Texas Instruments | LM25574-Q1 42-V, 0.5-A Step-Down Switching Regulator | Datasheet | Texas Instruments LM25574-Q1 42-V, 0.5-A Step-Down Switching Regulator Datasheet

Texas Instruments LM25574-Q1 42-V, 0.5-A Step-Down Switching Regulator Datasheet
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LM25574-Q1
SNVSB19 – DECEMBER 2017
LM25574-Q1 42-V, 0.5-A Step-Down Switching Regulator
1 Features
3 Description
•
•
The LM25574-Q1 is an easy to use buck regulator
which allows design engineers to design and optimize
a robust power supply using a minimum set of
components. Operating with an input voltage range of
6 V to 42 V, the LM25574-Q1 delivers 0.5-A of
continuous output current with an integrated 750-mΩ
N-Channel MOSFET. The regulator utilizes an
Emulated Current Mode architecture which provides
inherent line regulation, tight load transient response,
and ease of loop compensation without the usual
limitation of low-duty cycles associated with current
mode regulators. The operating frequency is
adjustable from 50 kHz to 1-MHz to allow
optimization of size and efficiency. To reduce EMI, a
frequency synchronization pin allows multiple IC’s
from the LM(2)557x family to self-synchronize or to
synchronize to an external clock. The LM25574-Q1
guarantees robustness with cycle-by-cycle current
limit, short-circuit protection, thermal shut-down, and
remote shut-down. The device is available in a
TSSOP-16 package.
1
•
•
•
•
•
•
•
•
•
•
•
•
Qualified for Automotive Applications
AEC-Q100 Qualified With the Following Results:
– Device Temperature Grade 1: –40°C to
+125°C Ambient Operating Temperature
Integrated 42-V, 750-mΩ N-Channel MOSFET
Ultra-Wide Input Voltage From 6 V to 42 V
Adjustable Output Voltage as Low as 1.225 V
1.5% Feedback Reference Accuracy
Operating Frequency Adjustable Between 50 kHz
and 1 MHz With Single Resistor
Master or Slave Frequency Synchronization
Adjustable Soft-Start
Emulated Current Mode Control Architecture
Wide Bandwidth Error Amplifier
Built-In Protection
TSSOP-16 Package
Create a Custom Design Using the LM25574-Q1
With the WEBENCH® Power Designer
Device Information(1)
PART NUMBER
2 Applications
•
LM25574-Q1
Industrial
PACKAGE
TSSOP (16)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Application Schematic
VIN
VIN
BST
SYNC
SW
VOUT
LM25574-Q1
SD
IS
RT
VCC
SS
RAMP
OUT
FB
COMP
GND
Copyright © 2017, Texas Instruments Incorporated
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM25574-Q1
SNVSB19 – DECEMBER 2017
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
5
6.1
6.2
6.3
6.4
6.5
6.6
5
5
5
5
5
7
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
7.4 Device Functional Modes........................................ 11
8
Application and Implementation ........................ 17
8.1 Application Information............................................ 17
8.2 Typical Application ................................................. 23
9
Layout ................................................................... 24
9.1 Layout Guidelines ................................................... 24
9.2 Layout Example ...................................................... 25
10 Device and Documentation Support ................. 27
10.1
10.2
10.3
10.4
10.5
10.6
Detailed Description ............................................ 10
7.1 Overview ................................................................. 10
7.2 Functional Block Diagram ....................................... 10
7.3 Feature Description................................................. 10
Device Support......................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
27
27
27
27
27
27
11 Mechanical, Packaging, and Orderable
Information ........................................................... 28
4 Revision History
2
DATE
REVISION
NOTES
December 2017
*
Initial release.
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5 Pin Configuration and Functions
PW
16-Pin TSSOP
Top View
1
VCC
BST
SD
PRE
VIN
SW
2
3
4
5
6
7
8
SYNC
IS
COMP
PGND
FB
OUT
RT
SS
RAMP
AGND
16
15
14
13
12
11
10
9
Pin Functions
PIN
NO.
NAME
1
VCC
DESCRIPTION
Output of the bias regulator
VCC tracks VIN up to 9 V. Beyond 9 V, VCC is regulated to 7 Volts. A 0.1 uF to 1 uF ceramic decoupling
capacitor is required. An external voltage (7.5 V – 14 V) can be applied to this pin to reduce internal power
dissipation.
2
SD
Shutdown or UVLO input
If the SD pin voltage is below 0.7 V the regulator will be in a low power state. If the SD pin voltage is between
0.7 V and 1.225 V the regulator will be in standby mode. If the SD pin voltage is above 1.225 V the regulator
will be operational. An external voltage divider can be used to set a line undervoltage shutdown threshold. If
the SD pin is left open circuit, a 5 µA pull-up current source configures the regulator fully operational.
3
VIN
Input supply voltage
Nominal operating range: 6 V to 42 V
4
SYNC
Oscillator synchronization input or output
The internal oscillator can be synchronized to an external clock with an external pull-down device. Multiple
LM25574-Q1 devices can be synchronized together by connection of their SYNC pins.
5
COMP
Output of the internal error amplifier
The loop compensation network should be connected between this pin and the FB pin.
6
FB
Feedback signal from the regulated output
This pin is connected to the inverting input of the internal error amplifier. The regulation threshold is 1.225 V.
7
RT
Internal oscillator frequency set input
The internal oscillator is set with a single resistor, connected between this pin and the AGND pin.
8
RAMP
Ramp control signal
An external capacitor connected between this pin and the AGND pin sets the ramp slope used for current
mode control. Recommended capacitor range 50 pF to 2000 pF.
9
AGND
Analog ground
Internal reference for the regulator control functions
10
SS
11
OUT
12
PGND
13
IS
14
SW
Soft-start
An external capacitor and an internal 10 µA current source set the time constant for the rise of the error amp
reference. The SS pin is held low during standby, VCC UVLO and thermal shutdown.
Output voltage connection
Connect directly to the regulated output voltage.
Power ground
Low side reference for the PRE switch and the IS sense resistor.
Current sense
Current measurement connection for the re-circulating diode. An internal sense resistor and a sample/hold
circuit sense the diode current near the conclusion of the off-time. This current measurement provides the DC
level of the emulated current ramp.
Switching node
The source terminal of the internal buck switch. The SW pin should be connected to the external Schottky
diode and to the buck inductor.
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Pin Functions (continued)
PIN
NO.
4
DESCRIPTION
NAME
15
PRE
Pre-charge assist for the bootstrap capacitor
This open drain output can be connected to SW pin to aid charging the bootstrap capacitor during very light
load conditions or in applications where the output may be pre-charged before the LM25574-Q1 is enabled.
An internal pre-charge MOSFET is turned on for 250 ns each cycle just prior to the on-time interval of the
buck switch.
16
BST
Boost input for bootstrap capacitor
An external capacitor is required between the BST and the SW pins. A 0.022 µF ceramic capacitor is
recommended. The capacitor is charged from VCC via an internal diode during the off-time of the buck switch.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MAX
UNIT
VIN to GND
MIN
45
V
BST to GND
60
V
PRE to GND
45
V
–1.5
V
BST to VCC
45
V
SD, VCC to GND
14
V
BST to SW
14
V
VIN
V
SW to GND (Steady State)
OUT to GND
Limited
SYNC, SS, FB, RAMP to GND
Storage temperature, Tstg
(1)
(2)
–65
7
V
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
Human-body model (HBM), per AEC Q100-002
VALUE
UNIT
±2
kV
(1)
AEC Q100-002 indicates that HBM stressing shall be in accordance with the ANSI/ESDA/JEDEC JS-001 specification.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
VIN
TJ Operation junction temperature
MAX
UNIT
6
42
V
–40
125
°C
6.4 Thermal Information
LM25574-Q1
THERMAL METRIC (1)
PW (TSSOP)
UNIT
16 PINS
RθJA
Junction-to-ambient thermal resistance
90
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
30
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
6.5 Electrical Characteristics
at TJ = 25°C, and VIN = 24 V, RT = 32.4 kΩ (unless otherwise noted). (1)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
6.85
7.15
7.45
V
STARTUP REGULATOR
VCCReg
VCC Regulator Output
TJ = –40°C to +125°C
VCC LDO Mode turn-off
VCC Current Limit
VCC = 0 V
9
V
25
mA
VCC SUPPLY
(1)
Min and Max limits are 100% production tested at 25°C. Limits over the operating temperature range are assured through correlation
using Statistical Quality Control (SQC) methods. Limits are used to calculate Texas Instruments' Average Outgoing Quality Level
(AOQL).
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Electrical Characteristics (continued)
at TJ = 25°C, and VIN = 24 V, RT = 32.4 kΩ (unless otherwise noted).(1)
PARAMETER
VCC UVLO Threshold
TEST CONDITIONS
(VCC increasing)
TJ = –40°C to +125°C
MIN
TYP
MAX
UNIT
5.03
5.35
5.67
V
VCC Undervoltage Hysteresis
0.35
V
Bias Current (Iin)
FB = 1.3 V
TJ = –40°C to +125°C
3.7
4.5
mA
Shutdown Current (Iin)
SD = 0 V
TJ = –40°C to +125°C
48
70
µA
(SD Increasing)
TJ = –40°C to +125°C
0.7
0.9
V
SHUTDOWN THRESHOLDS
Shutdown Threshold
0.47
Shutdown Hysteresis
Standby Threshold
0.1
(Standby Increasing)
TJ = –40°C to +125°C
1.17
1.225
V
1.28
V
Standby Hysteresis
0.1
V
SD Pull-up Current Source
5
µA
SWITCH CHARACTERSICS
Buck Switch Rds(on)
TJ = –40°C to +125°C
750
1500
mΩ
BOOST UVLO
4
V
BOOST UVLO Hysteresis
0.56
V
Pre-charge Switch Rds(on)
70
Ω
Pre-charge Switch on-time
250
ns
CURRENT LIMIT
Cycle by Cycle Current Limit
RAMP = 0 V
Cycle by Cycle Current Limit
Delay
RAMP = 2.5 V
TJ = –40°C to +125°C
0.6
0.7
0.8
75
A
ns
SOFT-START
SS Current Source
TJ = –40°C to +125°C
7
10
14
µA
Frequency 1
TJ = –40°C to +125°C
180
200
220
kHz
Frequency 2
RT = 11 kΩ
425
485
545
kHz
OSCILLATOR
TJ = –40°C to +125°C
SYNC Source Impedance
11
kΩ
SYNC Sink Impedance
110
Ω
SYNC Threshold (falling)
1.3
SYNC Frequency
RT = 11 kΩ
SYNC Pulse Width Minimum
TJ = –40°C to +125°C
TJ = –40°C to +125°C
V
550
kHz
15
ns
RAMP GENERATOR
Ramp Current 1
VIN = 36 V,
VOUT = 10 V
TJ = –40°C to +125°C
272
310
368
µA
Ramp Current 2
VIN = 10 V,
VOUT = 10 V
TJ = –40°C to +125°C
36
50
64
µA
416
500
575
ns
PWM COMPARATOR
Forced Off-time
6
TJ = –40°C to +125°C
Min On-time
80
ns
COMP to PWM Comparator
Offset
0.7
V
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Electrical Characteristics (continued)
at TJ = 25°C, and VIN = 24 V, RT = 32.4 kΩ (unless otherwise noted).(1)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
1.207
1.225
1.243
UNIT
ERROR AMPLIFIER
Feedback Voltage
Vfb = COMP
TJ = –40°C to +125°C
FB Bias Current
17
DC Gain
70
COMP Sink / Source Current
TJ = –40°C to +125°C
V
nA
dB
3
mA
Unity Gain Bandwidth
3
MHz
250
mΩ
Thermal Shutdown Threshold
165
°C
Thermal Shutdown Hysteresis
25
°C
DIODE SENSE RESISTANCE
DSENSE
THERMAL SHUTDOWN
Tsd
6.6 Typical Characteristics
100
10
1
10
100
1000
NORMALIZED OSCILLATOR FREQUENCY
OSCILLATOR FREQUENCY (kHz)
1000
1.010
1.005
1.000
0.995
0.990
-50
-25
0
25
50
75
100
125
RT (k:)
o
TEMPERATURE ( C)
FOSC = 200 kHz
Figure 1. Oscillator Frequency vs RT
Figure 2. Oscillator Frequency vs Temperature
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1.10
8
1.05
6
VCC (V)
NORMALIZED SOFTSTART CURRENT
Typical Characteristics (continued)
1.00
4
0.95
2
0.90
-50
-25
0
25
50
75
100
0
125
0
12
8
4
TEMPERATURE (oC)
16
20
24
ICC (mA)
VIN = 12V
Figure 4. VCC vs ICC
Figure 3. Soft Start Current vs Temperature
10
50
225
40
180
30
135
4
Ramp Down
20
PHASE
10
45
0
0
GAIN
-10
2
-45
Ramp Up
-20
0
0
2
4
6
8
10
-90
-30
10k
VIN (V)
8
90
PHASE (°)
6
GAIN (dB)
VCC (V)
8
100k
1M
10M
-135
100M
FREQUENCY (Hz)
RL = 7 kΩ
AVCL = 101
Figure 5. VCC vs VIN
Figure 6. Error Amplifier Gain and Phase
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Typical Characteristics (continued)
100
VIN = 7V
90
EFFICIENCY (%)
80
70
VIN = 24V
60
50
40
30
20
10
0
0.1
0.2
0.3
0.4
0.5
IOUT (A)
Figure 7. Demoboard Efficiency vs IOUT and VIN
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7 Detailed Description
7.1 Overview
The LM25574-Q1 switching regulator features all of the functions necessary to implement an efficient high
voltage buck regulator using a minimum of external components. This easy to use regulator integrates a 42-V NChannel buck switch with an output current capability of 0.5 Amps. The regulator control method is based on
current mode control utilizing an emulated current ramp. Peak current mode control provides inherent line
voltage feed-forward, cycle-by-cycle current limiting, and ease of loop compensation. The use of an emulated
control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable processing of very
small duty cycles necessary in high input voltage applications. The operating frequency is user programmable
from 50 kHz to 1 MHz. An oscillator synchronization pin allows multiple LM25574-Q1 regulators to self
synchronize or be synchronized to an external clock. The output voltage can be set as low as 1.225 V. Fault
protection features include, current limiting, thermal shutdown and remote shutdown capability. The device is
available in the TSSOP-16 package.
The functional block diagram and typical application of the LM25574-Q1 are shown in Functional Block Diagram.
The LM25574-Q1 can be applied in numerous applications to efficiently step-down a high, unregulated input
voltage. The device is well suited for telecom, industrial and automotive power bus voltage ranges.
7.2 Functional Block Diagram
VIN
7V ± 42 V
C1
1.0
VIN
3
5 PA
R1
OPEN
LM25574-Q1
VCC
7V
REGULATOR
1.225 V
2 SD
STANDBY
SHUTDOWN
SD
0.7 V
C2
OPEN
R2
OPEN
10 SS
BST
UVLO
C7
0.022
DRIVER
S Q
1.225 V
16
VIN
DIS
CLK
10 PA
C4
0.01
C8
0.47
THERMAL
SHUTDOWN
UVLO
1
R Q
LEVEL
SHIFT
SW 14
L1
100 PH
5V
PWM
0.7 V
PRE 15
C_LIMIT
6 FB
C6
open
C5
0.022
R4
24.9 k
ERROR
AMP
1.4 V
2V/A
+
5 COMP
CLK
Ir
OSCILLATOR
SYNC
4
RAMP
8
RT
7
SYNC
R3
21k
D1
CMSH2-60M
CLK
VIN
TRACK
SAMPLE
and
HOLD
RAMP GENERATOR
Ir = (10 PA x (VIN ± VOUT))
+ 50 PA
IS
13
PGND 12
AGND 9
CLK
OUT
11
C9
22
R5
5.11 k
R6
1.65 k
C3
470p
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7.3 Feature Description
7.3.1 High Voltage Start-Up Regulator
The LM25574-Q1 contains a dual-mode internal high voltage startup regulator that provides the VCC bias supply
for the PWM controller and boot-strap MOSFET gate driver. The input pin (VIN) can be connected directly to the
input voltage, as high as 42 Volts. For input voltages below 9 V, a low dropout switch connects VCC directly to
VIN. In this supply range, VCC is approximately equal to VIN. For VIN voltage greater than 9 V, the low dropout
switch is disabled and the VCC regulator is enabled to maintain VCC at approximately 7 V. The wide operating
range of 6 V to 42 V is achieved through the use of this dual mode regulator.
10
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Feature Description (continued)
The output of the VCC regulator is current limited to 25 mA. Upon power up, the regulator sources current into the
capacitor connected to the VCC pin. When the voltage at the VCC pin exceeds the VCC UVLO threshold of 5.35
V and the SD pin is greater than 1.225 V, the output switch is enabled and a soft-start sequence begins. The
output switch remains enabled until VCC falls below 5 V or the SD pin falls below 1.125 V.
An auxiliary supply voltage can be applied to the VCC pin to reduce the IC power dissipation. If the auxiliary
voltage is greater than 7.3 V, the internal regulator will essentially shut off, reducing the IC power dissipation.
The VCC regulator series pass transistor includes a diode between VCC and VIN that should not be forward biased
in normal operation. Therefore the auxiliary VCC voltage should never exceed the VIN voltage.
In high voltage applications extra care should be taken to ensure the VIN pin does not exceed the absolute
maximum voltage rating of 45 V. During line or load transients, voltage ringing on the VIN line that exceeds the
Absolute Maximum Ratings can damage the IC. Both careful PC board layout and the use of quality bypass
capacitors located close to the VIN and GND pins are essential.
VIN
9V
VCC
7V
5.25V
Internal Enable Signal
Figure 8. VIN and VCC Sequencing
7.4 Device Functional Modes
7.4.1 Shutdown and Stand-by Mode
The LM25574-Q1 contains a dual level Shutdown (SD) circuit. When the SD pin voltage is below 0.7 V, the
regulator is in a low current shutdown mode. When the SD pin voltage is greater than 0.7 V but less than 1.225
V, the regulator is in standby mode. In standby mode the VCC regulator is active but the output switch is disabled.
When the SD pin voltage exceeds 1.225 V, the output switch is enabled and normal operation begins. An internal
5 µA pull-up current source configures the regulator to be fully operational if the SD pin is left open.
An external set-point voltage divider from VIN to GND can be used to set the operational input range of the
regulator. The divider must be designed such that the voltage at the SD pin will be greater than 1.225 V when
VIN is in the desired operating range. The internal 5 µA pull-up current source must be included in calculations of
the external set-point divider. Hysteresis of 0.1 V is included for both the shutdown and standby thresholds. The
SD pin is internally clamped with a 1 kΩ resistor and an 8 V zener clamp. The voltage at the SD pin should never
exceed 14 V. If the voltage at the SD pin exceeds 8 V, the bias current will increase at a rate of 1 mA/V.
The SD pin can also be used to implement various remote enable and disable functions. Pulling the SD pin
below the 0.7 V threshold totally disables the controller. If the SD pin voltage is above 1.225 V the regulator will
be operational.
7.4.2 Oscillator and Sync Capability
The LM25574-Q1 oscillator frequency is set by a single external resistor connected between the RT pin and the
AGND pin. The RT resistor should be located very close to the device and connected directly to the pins of the IC
(RT and AGND).To set a desired oscillator frequency (F), the necessary value for the RT resistor can be
calculated Equation 1:
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Device Functional Modes (continued)
RT =
1 - 580 x 10-9
F
135 x 10-12
(1)
The SYNC pin can be used to synchronize the internal oscillator to an external clock. The external clock must be
of higher frequency than the free-running frequency set by the RT resistor. A clock circuit with an open drain
output is the recommended interface from the external clock to the SYNC pin. The clock pulse duration should
be greater than 15 ns.
LM25574-Q1
SYNC
SW
SYNC
AGND
CLK
SW
500 ns
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Figure 9. Sync from External Clock
LM25574-Q1
SYNC
LM25574-Q1
SYNC
UP TO 5
TOTAL
DEVICES
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Figure 10. Sync from Multiple Devices
Multiple LM25574-Q1 devices can be synchronized together simply by connecting the SYNC pins together. In
this configuration all of the devices will be synchronized to the highest frequency device. The diagram in
Figure 11 illustrates the SYNC input/output features of the LM25574-Q1. The internal oscillator circuit drives the
SYNC pin with a strong pull-down and weak pull-up inverter. When the SYNC pin is pulled low either by the
internal oscillator or an external clock, the ramp cycle of the oscillator is terminated and a new oscillator cycle
begins. Thus, if the SYNC pins of several LM25574-Q1 IC’s are connected together, the IC with the highest
internal clock frequency will pull the connected SYNC pins low first and terminate the oscillator ramp cycles of
the other IC’s. The LM25574-Q1 with the highest programmed clock frequency will serve as the master and
control the switching frequency of the all the devices with lower oscillator frequency.
12
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Device Functional Modes (continued)
5V
SYNC
10k
I = f(RT)
2.5V
Q
S
Q
R
DEADTIME
ONE-SHOT
Figure 11. Simplified Oscillator Block Diagram and SYNC I/O Circuit
7.4.3 Error Amplifier and PWM Comparator
The internal high gain error amplifier generates an error signal proportional to the difference between the
regulated output voltage and an internal precision reference (1.225 V). The output of the error amplifier is
connected to the COMP pin allowing the user to provide loop compensation components, generally a type II
network, as illustrated in Functional Block Diagram. This network creates a pole at DC, a zero and a noise
reducing high frequency pole. The PWM comparator compares the emulated current sense signal from the
RAMP generator to the error amplifier output voltage at the COMP pin.
7.4.4 Ramp Generator
The ramp signal used in the pulse width modulator for current mode control is typically derived directly from the
buck switch current. This switch current corresponds to the positive slope portion of the output inductor current.
Using this signal for the PWM ramp simplifies the control loop transfer function to a single pole response and
provides inherent input voltage feed-forward compensation. The disadvantage of using the buck switch current
signal for PWM control is the large leading edge spike due to circuit parasitics that must be filtered or blanked.
Also, the current measurement may introduce significant propagation delays. The filtering, blanking time and
propagation delay limit the minimum achievable pulsewidth. In applications where the input voltage may be
relatively large in comparison to the output voltage, controlling small pulsewidths and duty cycles is necessary for
regulation. The LM25574-Q1 utilizes a unique ramp generator, which does not actually measure the buck switch
current but rather reconstructs the signal. Reconstructing or emulating the inductor current provides a ramp
signal to the PWM comparator that is free of leading edge spikes and measurement or filtering delays. The
current reconstruction is comprised of two elements; a sample and hold DC level and an emulated current ramp.
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Device Functional Modes (continued)
RAMP
(10 µ x (VIN ± VOUT) + 50 µ) x
tON
CRAMP
Sample and
Hold DC Level
2V/A
TON
Figure 12. Composition of Current Sense Signal
The sample and hold DC level illustrated in Figure 12 is derived from a measurement of the re-circulating
Schottky diode anode current. The re-circulating diode anode should be connected to the IS pin. The diode
current flows through an internal current sense resistor between the IS and PGND pins. The voltage level across
the sense resistor is sampled and held just prior to the onset of the next conduction interval of the buck switch.
The diode current sensing and sample and hold provide the DC level of the reconstructed current signal. The
positive slope inductor current ramp is emulated by an external capacitor connected from the RAMP pin to AGND
and an internal voltage controlled current source. The ramp current source that emulates the inductor current is a
function of the Vin and Vout voltages per Equation 2:
IRAMP = (10 µ × (VIN – VOUT)) + 50 µA
(2)
Proper selection of the RAMP capacitor depends upon the selected value of the output inductor. The value of
CRAMP can be selected from: CRAMP = L × 5 × 10-6, where L is the value of the output inductor in Henrys. With this
value, the scale factor of the emulated current ramp will be approximately equal to the scale factor of the DC
level sample and hold (2.0 V / A). The CRAMP capacitor should be located very close to the device and connected
directly to the pins of the IC (RAMP and AGND).
For duty cycles greater than 50%, peak current mode control circuits are subject to sub-harmonic oscillation.
Sub-harmonic oscillation is normally characterized by observing alternating wide and narrow pulses at the switch
node. Adding a fixed slope voltage ramp (slope compensation) to the current sense signal prevents this
oscillation. The 50 µA of offset current provided from the emulated current source adds some fixed slope to the
ramp signal. In some high output voltage, high duty cycle applications, additional slope may be required. In these
applications, a pull-up resistor may be added between the VCC and RAMP pins to increase the ramp slope
compensation.
For VOUT > 7.5 V:
Calculate optimal slope current, IOS = VOUT x 10 µA/V.
For example, at VOUT = 10 V, IOS = 100 µA.
Install a resistor from the RAMP pin to VCC:
RRAMP = VCC / (IOS - 50 µA)
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Device Functional Modes (continued)
VCC
RRAMP
RAMP
CRAMP
Figure 13. RRAMP to VCC for VOUT > 7.5 V
7.4.5 Maximum Duty Cycle and Input Drop-out Voltage
There is a forced off-time of 500 ns implemented each cycle to guarantee sufficient time for the diode current to
be sampled. This forced off-time limits the maximum duty cycle of the buck switch. The maximum duty cycle will
vary with the operating frequency.
DMAX = 1 - Fs x 500 ns
(3)
Where Fs is the oscillator frequency. Limiting the maximum duty cycle will raise the input dropout voltage. The
input dropout voltage is the lowest input voltage required to maintain regulation of the output voltage. An
approximation of the input dropout voltage is:
VinMIN =
Vout + VD
1 - Fs x 500 ns
(4)
Where VD is the voltage drop across the re-circulatory diode. Operating at high switching frequency raises the
minimum input voltage necessary to maintain regulation.
7.4.6 Current Limit
The LM25574-Q1 contains a unique current monitoring scheme for control and over-current protection. When set
correctly, the emulated current sense signal provides a signal which is proportional to the buck switch current
with a scale factor of 2.0 V / A. The emulated ramp signal is applied to the current limit comparator. If the
emulated ramp signal exceeds 1.4 V (0.7 A) the present current cycle is terminated (cycle-by-cycle current
limiting). In applications with small output inductance and high input voltage the switch current may overshoot
due to the propagation delay of the current limit comparator. If an overshoot should occur, the diode current
sampling circuit will detect the excess inductor current during the off-time of the buck switch. If the sample and
hold DC level exceeds the 1.4 V current limit threshold, the buck switch will be disabled and skip pulses until the
diode current sampling circuit detects the inductor current has decayed below the current limit threshold. This
approach prevents current runaway conditions due to propagation delays or inductor saturation since the inductor
current is forced to decay following any current overshoot.
7.4.7 Soft-Start
The soft-start feature allows the regulator to gradually reach the initial steady state operating point, thus reducing
start-up stresses and surges. The internal soft-start current source, set to 10 µA, gradually increases the voltage
of an external soft-start capacitor connected to the SS pin. The soft-start capacitor voltage is connected to the
reference input of the error amplifier. Various sequencing and tracking schemes can be implemented using
external circuits that limit or clamp the voltage level of the SS pin.
In the event a fault is detected (over-temperature, VCC UVLO, SD) the soft-start capacitor will be discharged.
When the fault condition is no longer present a new soft-start sequence will commence.
7.4.8 Boost Pin
The LM25574-Q1 integrates an N-Channel buck switch and associated floating high voltage level shift / gate
driver. This gate driver circuit works in conjunction with an internal diode and an external bootstrap capacitor. A
0.022 µF ceramic capacitor, connected with short traces between the BST pin and SW pin, is recommended.
During the off-time of the buck switch, the SW pin voltage is approximately –0.5 V and the bootstrap capacitor is
charged from VCC through the internal bootstrap diode. When operating with a high PWM duty cycle, the buck
switch will be forced off each cycle for 500 ns to ensure that the bootstrap capacitor is recharged.
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Device Functional Modes (continued)
Under very light load conditions or when the output voltage is pre-charged, the SW voltage will not remain low
during the off-time of the buck switch. If the inductor current falls to zero and the SW pin rises, the bootstrap
capacitor will not receive sufficient voltage to operate the buck switch gate driver. For these applications, the
PRE pin can be connected to the SW pin to pre-charge the bootstrap capacitor. The internal pre-charge
MOSFET and diode connected between the PRE pin and PGND turns on each cycle for 250 ns just prior to the
onset of a new switching cycle. If the SW pin is at a normal negative voltage level (continuous conduction mode),
then no current will flow through the pre-charge MOSFET/diode.
7.4.9 Thermal Protection
Internal Thermal Shutdown circuitry is provided to protect the integrated circuit in the event the maximum junction
temperature is exceeded. When activated, typically at 165°C, the controller is forced into a low power reset state,
disabling the output driver and the bias regulator. This feature is provided to prevent catastrophic failures from
accidental device overheating.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 External Components
The procedure for calculating the external components is illustrated with the following design example. The Bill of
Materials for this design is listed in Table 1. The circuit shown in Functional Block Diagram is configured for the
following specifications:
• VOUT = 5 V
• VIN = 7 V to 42 V
• Fs = 300 kHz
• Minimum load current (for CCM) = 100 mA
• Maximum load current = 0.5 A
8.1.2 R3 (RT)
RT sets the oscillator switching frequency. Generally, higher frequency applications are smaller but have higher
losses. Operation at 300 kHz was selected for this example as a reasonable compromise for both small size and
high efficiency. The value of RT for 300 kHz switching frequency can be calculated in Equation 5:
[(1 / 300 x 103) – 580 x 10-9]
RT =
135 x 10-12
(5)
The nearest standard value of 21 kΩ was chosen for RT.
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Application Information (continued)
8.1.3 L1
The inductor value is determined based on the operating frequency, load current, ripple current, and the
minimum and maximum input voltage (VIN(min), VIN(max)).
L1 Current
IPK+
IRIPPLE
IO
IPK-
1/Fs
0 mA
Figure 14. Inductor Current Waveform
To keep the circuit in continuous conduction mode (CCM), the maximum ripple current IRIPPLE should be less
than twice the minimum load current, or 0.2 Ap-p. Using this value of ripple current, the value of inductor (L1) is
calculated using the following:
L1 =
VOUT x (VIN(max) – VOUT)
L1 =
IRIPPLE x FS x VIN(max)
(6)
5V x (42V - 5V)
= 73 PH
0.2A x 300 kHz x 42V
(7)
This procedure provides a guide to select the value of L1. The nearest standard value (100 µH) will be used. L1
must be rated for the peak current (IPK+) to prevent saturation. During normal loading conditions, the peak current
occurs at maximum load current plus maximum ripple. During an overload condition the peak current is limited to
0.7 A nominal (0.85 A maximum). The selected inductor (see Table 1) has a conservative 1.0 Amp saturation
current rating. For this manufacturer, the saturation rating is defined as the current necessary for the inductance
to reduce by 30%, at 20°C.
8.1.4 C3 (CRAMP)
With the inductor value selected, the value of C3 (CRAMP) necessary for the emulation ramp circuit is:
CRAMP = L × 5 × 10-6
(8)
Where L is in Henrys
With L1 selected for 100 µH the recommended value for C3 is 470 pF (nearest standard value).
8.1.5 C9
The output capacitor, C9 smoothes the inductor ripple current and provides a source of charge for transient
loading conditions. For this design a 22 µF ceramic capacitor was selected. The ceramic capacitor provides ultra
low ESR to reduce the output ripple voltage and noise spikes. An approximation for the output ripple voltage is:
§
¨
©
§
1
'VOUT = 'IL x ¨ESR +
8
x
F
x COUT
S
©
(9)
8.1.6 C1
The regulator supply voltage has a large source impedance at the switching frequency. Good quality input
capacitors are necessary to limit the ripple voltage at the VIN pin while supplying most of the switch current
during the on-time. When the buck switch turns on, the current into the VIN pin steps to the lower peak of the
inductor current waveform, ramps up to the peak value, then drops to zero at turn-off. The average current into
VIN during the on-time is the load current. The input capacitance should be selected for RMS current rating and
minimum ripple voltage. A good approximation for the required ripple current rating necessary is IRMS > IOUT / 2.
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Application Information (continued)
Quality ceramic capacitors with a low ESR should be selected for the input filter. To allow for capacitor
tolerances and voltage effects, one 1.0 µF, 100 V ceramic capacitor will be used. If step input voltage transients
are expected near the maximum rating of the LM25574-Q1, a careful evaluation of ringing and possible spikes at
the device VIN pin should be completed. An additional damping network or input voltage clamp may be required
in these cases.
8.1.7 C8
The capacitor at the VCC pin provides noise filtering and stability for the VCC regulator. The recommended value
of C8 should be no smaller than 0.1 µF, and should be a good quality, low ESR, ceramic capacitor. A value of
0.47 µF was selected for this design.
8.1.8 C7
The bootstrap capacitor between the BST and the SW pins supplies the gate current to charge the buck switch
gate at turn-on. The recommended value of C7 is 0.022 µF, and should be a good quality, low ESR, ceramic
capacitor.
8.1.9 C4
The capacitor at the SS pin determines the soft-start time, that is the time for the reference voltage and the
output voltage, to reach the final regulated value. The time is determined from Equation 10:
tss =
C4 x 1.225V
10 µA
(10)
For this application, a C4 value of 0.01 µF was chosen which corresponds to a soft-start time of 1 ms.
8.1.10 R5, R6
R5 and R6 set the output voltage level, the ratio of these resistors is calculated from Equation 11:
R5/R6 = (VOUT / 1.225 V) - 1
(11)
For a 5 V output, the R5 and R6 ratio calculates to 3.082. The resistors should be chosen from standard value
resistors, a good starting point is selection in the range of 1.0 kΩ - 10 kΩ. Values of 5.11 kΩ for R5, and 1.65 kΩ
for R6 were selected.
8.1.11 R1, R2, C2
A voltage divider can be connected to the SD pin to set a minimum operating voltage VIN(min) for the regulator. If
this feature is required, the easiest approach to select the divider resistor values is to select a value for R1
(between 10 kΩ and 100 kΩ recommended) then calculate R2 from Equation 12:
§
¨
©
§
R1
R2 = 1.225 x ¨
-6
V
+
(5
x
10
x R1) ± 1.225
© IN(min)
(12)
Capacitor C2 provides filtering for the divider. The voltage at the SD pin should never exceed 8 V, when using an
external set-point divider it may be necessary to clamp the SD pin at high input voltage conditions. The reference
design utilizes the full range of the LM25574-Q1 (6 V to 42 V); therefore these components can be omitted. With
the SD pin open circuit the LM25574-Q1 responds once the VCC UVLO threshold is satisfied.
8.1.12 R4, C5, C6
These components configure the error amplifier gain characteristics to accomplish a stable overall loop gain. One
advantage of current mode control is the ability to close the loop with only two feedback components, R4 and C5.
The overall loop gain is the product of the modulator gain and the error amplifier gain. The DC modulator gain of
the LM25574-Q1 is as follows:
DC Gain(MOD) = Gm(MOD) x RLOAD = 0.5 × RLOAD
(13)
The dominant low frequency pole of the modulator is determined by the load resistance (RLOAD,) and output
capacitance (COUT). The corner frequency of this pole is:
fp(MOD) = 1 / (2π RLOAD COUT)
(14)
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Application Information (continued)
For RLOAD = 20 Ω and COUT = 22 µF then fp(MOD) = 362 Hz
DC Gain(MOD) = 0.5 x 20 = 20 dB
For the design example of Functional Block Diagram the following modulator gain vs. frequency characteristic
was measured as shown in Figure 15.
REF LEVEL
0.000 dB
0.0 deg
/DIV
10.000 dB
45.000 deg
GAIN
0
PHASE
100
1k
START 100.000 Hz
10k
100k
STOP 100 000.000 Hz
Figure 15. Gain and Phase of Modulator RLOAD = 20 Ohms and COUT = 22µF
Components R4 and C5 configure the error amplifier as a type II configuration which has a pole at DC and a
zero at fZ = 1 / (2πR4C5). The error amplifier zero cancels the modulator pole leaving a single pole response at
the crossover frequency of the loop gain. A single pole response at the crossover frequency yields a very stable
loop with 90 degrees of phase margin.
For the design example, a target loop bandwidth (crossover frequency) of 25 kHz was selected. The
compensation network zero (fZ) should be selected at least an order of magnitude less than the target crossover
frequency. This constrains the product of R4 and C5 for a desired compensation network zero 1 / (2π R4 C5) to
be less than 2 kHz. Increasing R4, while proportionally decreasing C5, increases the error amp gain. Conversely,
decreasing R4 while proportionally increasing C5, decreases the error amp gain. For the design example C5 was
selected for 0.022 µF and R4 was selected for 24.9 kΩ. These values configure the compensation network zero
at 290 Hz. The error amp gain at frequencies greater than fZ is: R4 / R5, which is approximately 5 (14 dB).
REF LEVEL
0.000 dB
0.0 deg
/DIV
10.000 dB
45.000 deg
PHASE
GAIN
0
100
1k
START 100.000 Hz
10k
100k
STOP 100 000.000 Hz
Figure 16. Error Amplifier Gain and Phase
The overall loop can be predicted as the sum (in dB) of the modulator gain and the error amp gain.
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Application Information (continued)
REF LEVEL
0.000 dB
0.0 deg
/DIV
10.000 dB
45.000 deg
GAIN
PHASE
0
100
1k
START 100.000 Hz
10k
100k
STOP 100 000.000 Hz
Figure 17. Overall Loop Gain and Phase
If a network analyzer is available, the modulator gain can be measured and the error amplifier gain can be
configured for the desired loop transfer function. If a network analyzer is not available, the error amplifier
compensation components can be designed with the guidelines given. Step load transient tests can be
performed to verify acceptable performance. The step load goal is minimum overshoot with a damped response.
C6 can be added to the compensation network to decrease noise susceptibility of the error amplifier. The value
of C6 must be sufficiently small since the addition of this capacitor adds a pole in the error amplifier transfer
function. This pole must be well beyond the loop crossover frequency. A good approximation of the location of
the pole added by C6 is: fp2 = fz x C5 / C6.
8.1.13 Bias Power Dissipation Reduction
Buck regulators operating with high input voltage can dissipate an appreciable amount of power for the bias of
the IC. The VCC regulator must step-down the input voltage VIN to a nominal VCC level of 7 V. The large voltage
drop across the VCC regulator translates into a large power dissipation within the VCC regulator. There are several
techniques that can significantly reduce this bias regulator power dissipation. Figure 18 and Figure 19 depict two
methods to bias the IC from the output voltage. In each case the internal VCC regulator is used to initially bias the
VCC pin. After the output voltage is established, the VCC pin potential is raised above the nominal 7 V regulation
level, which effectively disables the internal VCC regulator. The voltage applied to the VCC pin should never
exceed 14 V. The VCC voltage should never be larger than the VIN voltage.
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Application Information (continued)
LM25574-Q1
BST
VOUT
SW
L1
COUT
D1
IS
GND
VCC
D2
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Figure 18. VCC Bias from VOUT for 8 V < VOUT < 14 V
LM25574-Q1
BST
L1
SW
D1
VOUT
COUT
IS
GND
D2
VCC
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Figure 19. VCC Bias with Additional Winding on the Output Inductor
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8.2 Typical Application
8.2.1 Typical Schematic for High Frequency (1 MHz) Application
BST
9 t 32 V
0.022 P 22 P
VIN
3.3V, 0.5A
SD
1P
SW
SYNC
5.11 k
LM25574-Q1
CMSH2-40
COMP
22 P
IS
24.9 k
3.01 k
GND
0.022 P
OUT
FB
RAMP RT
100 p
SS
VCC
3.5
7k
0.1 P
0.01 P
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9 Layout
9.1 Layout Guidelines
9.1.1 PCB Layout and Thermal Considerations
The circuit in Functional Block Diagram serves as both a block diagram of the LM25574-Q1 and a typical
application board schematic for the LM25574-Q1. In a buck regulator there are two loops where currents are
switched very fast. The first loop starts from the input capacitors, to the regulator VIN pin, to the regulator SW
pin, to the inductor then out to the load. The second loop starts from the output capacitor ground, to the regulator
PGND pins, to the regulator IS pins, to the diode anode, to the inductor and then out to the load. Minimizing the
loop area of these two loops reduces the stray inductance and minimizes noise and possible erratic operation. A
ground plane in the PC board is recommended as a means to connect the input filter capacitors to the output
filter capacitors and the PGND pins of the regulator. Connect all of the low power ground connections (CSS, RT,
CRAMP) directly to the regulator AGND pin. Connect the AGND and PGND pins together through the topside
copper trace. Place several vias in this trace to the ground plane.
The two highest power dissipating components are the re-circulating diode and the LM25574-Q1 regulator IC.
The easiest method to determine the power dissipated within the LM25574-Q1 is to measure the total conversion
losses (Pin – Pout) then subtract the power losses in the Schottky diode, output inductor and snubber resistor.
An approximation for the Schottky diode loss is P = (1-D) x Iout x Vfwd. An approximation for the output inductor
power is P = IOUT2 × R × 1.1, where R is the DC resistance of the inductor and the 1.1 factor is an approximation
for the AC losses. If a snubber is used, an approximation for the damping resistor power dissipation is P = VIN2 ×
Fsw × Csnub, where Fsw is the switching frequency and Csnub is the snubber capacitor.
The most significant variables that affect the power dissipated by the LM25574-Q1 are the output current, input
voltage and operating frequency. The power dissipated while operating near the maximum output current and
maximum input voltage can be appreciable. The operating frequency of the LM25574-Q1 evaluation board has
been designed for 300 kHz. When operating at 0.5 A output current with a 42 V input the power dissipation of the
LM25574-Q1 regulator is approximately 0.36 W.
The junction-to-ambient thermal resistance of the LM25574-Q1 will vary with the application. The most significant
variables are the area of copper in the PC board, and the amount of forced air cooling provided. The junction-toambient thermal resistance of the LM25574-Q1 mounted in the evaluation board varies from 90°C/W with no
airflow to 60°C/W with 900 LFM (Linear Feet per Minute). With a 25°C ambient temperature and no airflow, the
predicted junction temperature for the LM25574-Q1 will be 25 + (90 × 0.36) = 57°C. If the evaluation board is
operated at 0.5 A output current, 42 V input voltage and high ambient temperature for a prolonged period of time
the thermal shutdown protection within the IC may activate. The IC will turn off allowing the junction to cool,
followed by restart with the soft-start capacitor reset to zero.
Table 1. 5 V, 0.5 A Demo Board Bill of Materials
ITEM
24
PART NUMBER
DESCRIPTION
VALUE
C
1
C3225X7R2A105M
CAPACITOR, CER, TDK
C
2
OPEN
NOT USED
1 µ, 100 V
C
3
C0805A471K1GAC
CAPACITOR, CER, KEMET
470 p, 100 V
C
4
C2012X7R2A103K
CAPACITOR, CER, TDK
0.01 µ, 100 V
C
5
C2012X7R2A223K
CAPACITOR, CER, TDK
0.022 µ, 100 V
C
6
OPEN
NOT USED
C
7
C2012X7R2A223K
CAPACITOR, CER, TDK
0.022 µ, 100 V
C
8
C2012X7R1C474M
CAPACITOR, CER, TDK
0.47 µ, 16 V
C
9
C3225X7R1C226M
CAPACITOR, CER, TDK
22 µ, 16 V
D
1
CMSH2-60M
DIODE, 60V, CENTRAL
L
1
DR74-101
INDUCTOR, COOPER
R
1
OPEN
NOT USED
R
2
OPEN
NOT USED
R
3
CRCW08052102F
RESISTOR
21 kΩ
R
4
CRCW08052492F
RESISTOR
24.9 kΩ
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Layout Guidelines (continued)
Table 1. 5 V, 0.5 A Demo Board Bill of Materials (continued)
ITEM
PART NUMBER
DESCRIPTION
VALUE
R
5
CRCW08055111F
RESISTOR
5.11 kΩ
R
6
CRCW08051651F
RESISTOR
1.65 kΩ
U
1
LM25574-Q1
REGULATOR, TEXAS INSTRUMENTS
9.2 Layout Example
Figure 20. Component Side
Figure 21. Solder Side
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Layout Example (continued)
LM25574-Q1
Figure 22. Silkscreen
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10 Device and Documentation Support
10.1 Device Support
10.1.1 Developmental Support
10.1.1.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the LM25574-Q1 device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
• Run electrical simulations to see important waveforms and circuit performance
• Run thermal simulations to understand board thermal performance
• Export customized schematic and layout into popular CAD formats
• Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
10.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
10.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
10.4 Trademarks
E2E is a trademark of Texas Instruments.
WEBENCH is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
10.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
10.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
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Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: LM25574-Q1
27
LM25574-Q1
SNVSB19 – DECEMBER 2017
www.ti.com
11 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
28
Submit Documentation Feedback
Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: LM25574-Q1
PACKAGE OPTION ADDENDUM
www.ti.com
13-Oct-2017
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM25574QMT/NOPB
ACTIVE
TSSOP
PW
16
92
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
L25574
QMT
LM25574QMTX/NOPB
ACTIVE
TSSOP
PW
16
2500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
L25574
QMT
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
13-Oct-2017
OTHER QUALIFIED VERSIONS OF LM25574-Q1 :
• Catalog: LM25574
NOTE: Qualified Version Definitions:
• Catalog - TI's standard catalog product
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
19-Dec-2017
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
LM25574QMTX/NOPB
Package Package Pins
Type Drawing
TSSOP
PW
16
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
2500
330.0
12.4
Pack Materials-Page 1
6.95
B0
(mm)
K0
(mm)
P1
(mm)
5.6
1.6
8.0
W
Pin1
(mm) Quadrant
12.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
19-Dec-2017
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM25574QMTX/NOPB
TSSOP
PW
16
2500
367.0
367.0
35.0
Pack Materials-Page 2
PACKAGE OUTLINE
PW0016A
TSSOP - 1.2 mm max height
SCALE 2.500
SMALL OUTLINE PACKAGE
SEATING
PLANE
C
6.6
TYP
6.2
A
0.1 C
PIN 1 INDEX AREA
14X 0.65
16
1
2X
5.1
4.9
NOTE 3
4.55
8
9
B
0.30
0.19
0.1
C A B
16X
4.5
4.3
NOTE 4
1.2 MAX
(0.15) TYP
SEE DETAIL A
0.25
GAGE PLANE
0.15
0.05
0 -8
0.75
0.50
DETAIL A
A 20
TYPICAL
4220204/A 02/2017
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not
exceed 0.15 mm per side.
4. This dimension does not include interlead flash. Interlead flash shall not exceed 0.25 mm per side.
5. Reference JEDEC registration MO-153.
www.ti.com
EXAMPLE BOARD LAYOUT
PW0016A
TSSOP - 1.2 mm max height
SMALL OUTLINE PACKAGE
SYMM
16X (1.5)
(R0.05) TYP
1
16
16X (0.45)
SYMM
14X (0.65)
8
9
(5.8)
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE: 10X
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
METAL
SOLDER MASK
OPENING
EXPOSED METAL
EXPOSED METAL
0.05 MAX
ALL AROUND
NON-SOLDER MASK
DEFINED
(PREFERRED)
0.05 MIN
ALL AROUND
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
15.000
4220204/A 02/2017
NOTES: (continued)
6. Publication IPC-7351 may have alternate designs.
7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.
www.ti.com
EXAMPLE STENCIL DESIGN
PW0016A
TSSOP - 1.2 mm max height
SMALL OUTLINE PACKAGE
16X (1.5)
SYMM
(R0.05) TYP
1
16X (0.45)
16
SYMM
14X (0.65)
8
9
(5.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
SCALE: 10X
4220204/A 02/2017
NOTES: (continued)
8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
9. Board assembly site may have different recommendations for stencil design.
www.ti.com
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Copyright © 2019, Texas Instruments Incorporated
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