High-efficiency Buck Converter with Ultra-low

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TPS62748
SLVSD37A – SEPTEMBER 2015 – REVISED OCTOBER 2015
TPS62748 300 mA High Efficiency Buck Converter with Ultra-low Quiescent Current and
Load Switch
1 Features
3 Description
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The TPS62748 is a high efficiency step down
converter with ultra low quiescent current of typical
360 nA. The device is optimized to operate with a
2.2-µH inductor and 10µF output capacitor. The
device uses DCS-Control™ and operates with a
typical switching frequency of 1.2 MHz. In Power
Save Mode the device extends the light load
efficiency down to a load current range of 10-µA and
below. TPS62748 provides an output current of 300
mA. Once started the device operates down to an
input voltage range of 2.0 V. This allows to operate
the device directly from a single Li-MnO2 coin cell.
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Input Voltage Range VIN from 2.15 V to 5.5 V
Input Voltage Range Down to 2.0 V Once Started
300 mA Output Current
360 nA Operational Quiescent Current
Up to 90% Efficiency at 10-µA Output Current
Power Save Mode Operation
Selectable Output Voltages
– 1.2 V and 1.8 V
Output Voltage Discharge
100 mA/2.2 Ω Integrated Load Switch
Low Output Voltage Ripple
Automatic Transition to No Ripple 100% Mode
RF Friendly DCS-Control™
Total Solution Size <10mm2
Small 1.6 mm × 0.9 mm, 8 Ball WCSP Package
2 Applications
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Wearables
Fitness Tracker
Smart Watch
Health Monitoring
Bluetooth® Low Energy, RF4CE, Zigbee
High-efficiency, Ultra Low Power Applications
Energy Harvesting
The TPS62748 provides two programmable output
voltages of 1.2V and 1.8V selectable by one voltage
select pin. The TPS62748 is optimized to provide a
low output voltage ripple and low noise using a small
output capacitor. Once the input voltage comes close
to the output voltage the device enters the No Ripple
100% mode to prevent an increase of output ripple
voltage. In this operation mode the device stops
switching and turns the high side MOSFET switch on.
The TPS62748 has a 100 mA load switch between
pins VOS and LOAD with a typical ON-resistance of
0.6 Ohm. The load switch is typically used to
distribute the buck converter output voltage to the
sub-system.
Device Information(1)
PART NUMBER
TPS62748
PACKAGE
DSBGA (8)
BODY SIZE (NOM)
1.6 mm × 0.9 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Typical Application
CIN
4.7 PF
TPS62748
L 2.2 PH
100%
VOUT
VIN
SW
EN
VOS
VSEL
95%
90%
COUT
10 PF
Low Power
MCU & RF
CTRL
85%
Efficiency
VIN
2.0V to 5.5V
80%
75%
70%
65%
GND
LOAD
Sensor
60%
VIN = 3.6 V
VIN = 4.2 V
VIN = 5.0 V
55%
50%
0.001
0.01
0.1
1
IOUT (mA)
10
100
1000
D006
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.
TPS62748
SLVSD37A – SEPTEMBER 2015 – REVISED OCTOBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
9
Features ..................................................................
Applications ...........................................................
Description .............................................................
Typical Application ................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
1
2
3
3
4
8.1
8.2
8.3
8.4
8.5
8.6
8.7
4
4
4
5
5
6
7
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information .................................................
Electrical Characteristics...........................................
Timing Requirements ................................................
Typical Characteristics ..............................................
Detailed Description .............................................. 8
9.1 Overview ................................................................... 8
9.2 Functional Block Diagram ......................................... 8
9.3 Feature Description................................................... 8
9.4 Device Functional Modes........................................ 10
10 Application and Implementation........................ 11
10.1 Application Information.......................................... 11
10.2 Typical Application ............................................... 11
10.3 System Example ................................................... 16
11 Power Supply Recommendations ..................... 17
12 Layout................................................................... 17
12.1 Layout Guidelines ................................................. 17
12.2 Layout Example .................................................... 17
12.3 Package Dimensions ............................................ 17
13 Device and Documentation Support ................. 18
13.1
13.2
13.3
13.4
13.5
Device Support......................................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
18
18
18
18
18
14 Mechanical, Packaging, and Orderable
Information ........................................................... 18
5 Revision History
Changes from Original (September 2015) to Revision A
•
2
Page
Changed Feature bullet from "60 nA Operational Quiescent Current" to "360 nA Operational Quiescent Current" ............. 1
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6 Device Comparison Table
TA
PART NUMBER
–40°C to 85°C
OUTPUT VOLTAGE SETTINGS
TPS62748
1.2 V and 1.8 V (VSEL)
OUTPUT CURRENT
[mA]
PACKAGE
MARKING
300 mA
TPS748
7 Pin Configuration and Functions
YFP Package
8-Pin DSBGA
Top View
1
2
A
SW
VIN
B
EN
GND
C
VSEL
VOS
D
CTRL
LOAD
Pin Functions TPS62748
PIN
NAME
NO
VIN
A2
SW
GND
I/O
DESCRIPTION
PWR
VIN power supply pin. Connect the input capacitor close to this pin for best noise and voltage spike
suppression. A ceramic capacitor of 4.7 µF is required.
A1
OUT
The switch pin is connected to the internal MOSFET switches. Connect the inductor to this terminal.
B2
PWR
GND supply pin. Connect this pin close to the GND terminal of the input and output capacitor.
VOS
C2
IN
Feedback pin for the internal feedback divider network and regulation loop. An internal load switch is
connected between VOUT pin and LOAD pin. Connect this pin directly to the output capacitor with a short
trace. Discharges VOUT when the converter is disabled.
VSEL
C1
IN
Output voltage selection pin. See Table 1 for VOUT selection. This pin must be terminated. The pin can be
dynamically changed during operation.
EN
B1
IN
High level enables the devices, low level turns the device into shutdown mode. The pin must be
terminated.
CTRL
D1
IN
This pin controls the load switch between VOS and LOAD. With CTRL = low, the LOAD switch is disabled.
This pin must be terminated.
LOAD
D2
OUT
Output terminal of the internal load switch. With CTRL = high, the internal load switch connects VOS to the
LOAD pin. This pin is pulled to GND with the CTRL = low. If not used, leave the pin open.
Table 1. Output Voltage Setting TPS62748
Device
TPS62748
VOUT
VSEL
1.2
0
1.8
1
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8 Specifications
8.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1)
MIN
MAX
UNIT
VIN
–0.3
6
V
SW, VSEL, LOAD, CTRL
–0.3
VIN +0.3V
V
EN
–0.3
VIN +0.3V
V
VOS
–0.3
3.7
V
Operating junction temperature, TJ
–40
125
°C
Storage temperature, Tstg
–65
150
°C
Pin voltage (2)
(1)
(2)
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute–maximum–rated conditions for extended periods may affect device reliability.
All voltage values are with respect to network ground terminal GND.
8.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (1)
±2000
Charged device model (CDM), per JEDEC specification
JESD22-C101, all pins (2)
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. The human body
model is a 100-pF capacitor discharged through a 1.5-kΩ resistor into each pin.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
8.3 Recommended Operating Conditions
MIN NOM MAX
VIN
Supply voltage VIN
VIN
Supply voltage VIN , once started
IOUT
ILOAD
TJ
Operating junction temperature range
4
UNIT
2.15
5.5
V
2.0
5.5
V
Device output current
300
mA
Load switch current
100
mA
125
°C
-40
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8.4 Thermal Information
TPS62748
THERMAL METRIC (1)
YFP
UNIT
8 PINS
RθJA
Junction-to-ambient thermal resistance
103
°C/W
RθJCtop
Junction-to-case (top) thermal resistance
1.0
°C/W
RθJB
Junction-to-board thermal resistance
20
°C/W
ψJT
Junction-to-top characterization parameter
0.3
°C/W
ψJB
Junction-to-board characterization parameter
20
°C/W
RθJCbot
Junction-to-case (bottom) thermal resistance
N/A
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
8.5 Electrical Characteristics
VIN = 3.6V, TJ = –40°C to 125°C typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
1800
UNIT
SUPPLY
IQ
Operating
quiescent current
EN = VIN, CTRL = GND, IOUT = 0µA, VOUT = 1.8V, device not switching
360
EN = VIN, IOUT = 0mA, CTRL = GND, VOUT = 1.8V , device switching
460
ISD
Shutdown current
EN = GND, shutdown current into VIN
70
1000
Undervoltage
lockout threshold
Rising VIN
2.075
2.15
Falling VIN
1.925
2
VTH_ UVLO+
VTH_UVLO-
nA
nA
V
INPUTS (EN, VSEL, CTRL )
High level input
threshold
2.2V ≤ VIN ≤ 5.5V
VIL TH
Low level input
threshold
2.2V ≤ VIN ≤ 5.5V
IIN
Input bias Current
VIH
TH
1.1
0.4
V
V
10
25
0.45
1.12
0.22
0.65
600
720
nA
POWER SWITCHES
RDS(ON)
ILIMF
High side
MOSFET onresistance
Low Side
MOSFET onresistance
Ω
IOUT = 50mA
High side
MOSFET switch
current limit
480
Low side MOSFET
switch current limit
600
mA
mA
OUTPUT VOLTAGE DISCHARGE
RDSCH_VOS
MOSFET onresistance
EN = GND, IVOS = -10mA into VOS pin
30
65
Ω
IIN_VOS
Bias current into
VOS pin
EN = VIN, VOUT = 2V
40
1010
nA
RLOAD
MOSFET onresistance
ILOAD = 50mA, CTRL = VIN, VOUT = 1.8V, 2.2V ≤ VIN ≤ 5.5V
0.6
1.27
Ω
RDCHRG
MOSFET onresistance
2.2V ≤ VIN ≤ 5.5V; CTRL=GND
30
65
Ω
LOAD Switch
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Electrical Characteristics (continued)
VIN = 3.6V, TJ = –40°C to 125°C typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
150
250
350
85
200
290
80
150
200
UNIT
AUTO 100% MODE TRANSITION
VTH_100+
Auto 100% Mode
leave detection
threshold (1)
Rising VIN,100% Mode is left with VIN = VOUT + VTH_100+
VTH_100-
Auto 100% Mode
enter detection
threshold (1)
Falling VIN, 100% Mode is entered with VIN = VOUT + VTH_100-
mV
OUTPUT
ILIM_softstart
High side softstart
switch current limit
Low side softstart
switch current limit
Output voltage
range
Output voltage
accuracy
VOUT
(1)
EN=low to high
mA
150
Output voltages are selected with pins VSEL
1.2
IOUT = 10mA, VOUT = 1.8V
IOUT = 100mA, VOUT = 1.8V
DC output voltage
load regulation
VOUT = 1.8V
DC output voltage
line regulation
VOUT = 1.8V, IOUT = 100mA, 2.2V ≤ VIN ≤ 5.0V
1.8
-2.5
0%
2.5
–2
0%
2
0.001
V
%/mA
0
%/V
VIN is compared to the programmed output voltage (VOUT). When VIN–VOUT falls below VTH_100- the device enters 100% Mode by turning
the high side MOSFET on. The 100% Mode is exited when VIN–VOUT exceeds VTH_100+ and the device starts switching. The hysteresis
for the 100% Mode detection threshold VTH_100+ - VTH_100- will always be positive and will be approximately 50 mV(typ)
8.6 Timing Requirements
VIN = 3.6V, TJ = –40°C to 125°C typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
800
μs
LOAD Switch
VLOAD rise time
CTRL= low to high, VOUT = 1.8V, 2.2V ≤ VIN ≤ 5.5V, ILOAD = 20mA
tONmin
Minimum ON time
VOUT = 2.0V, IOUT = 0 mA
225
ns
tOFFmin
Minimum OFF time VIN = 2.3V
50
ns
tStartup_delay
Regulator start up
delay time
From transition EN = low to high until device starts switching
10
25
ms
tSoftstart
Softstart time
2.2V ≤ VIN ≤ 5.5V, EN = VIN
700
1200
µs
trise_LOAD
315
OUTPUT
6
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8.7 Typical Characteristics
250
700
VIN = 2.2 V
VIN = 2.5 V
VIN = 3.6 V
VIN = 5.5 V
VIN = 6.0 V
200
Shutdown Current (nA)
Quiescent Current (nA)
600
VIN = 2.2 V
VIN = 2.5 V
VIN = 3.6 V
VIN = 5.5 V
VIN = 6.0 V
225
500
400
175
150
125
100
75
50
300
25
200
-60
-40
-20
0
20
40
Temperature (qC)
EN = VIN, VOUT = 1.8V, CTRL = GND
60
80
0
-60
100
Device Not Switching
0
20
40
Temperature (qC)
60
80
100
D002
Figure 2. Shutdown Current ISD vs Temperature
1
0.5
0.9
0.45
0.4
Low Side RDSON (:)
0.8
High Side RDSON (:)
-20
EN = GND
Figure 1. Quiescent Current vs Temperature
0.7
0.6
0.5
0.4
0.3
0.2
-40
-20
0
20
40
Temperature (qC)
60
80
0.35
0.3
0.25
0.2
0.15
0.1
VIN = 2.2 V
VIN = 2.5 V
VIN = 3.6 V
0.1
0
-60
-40
D001
VIN = 2.2 V
VIN = 2.5 V
VIN = 3.6 V
0.05
100
0
-60
-40
D003
Figure 3. High Side RDSON vs Temperature
-20
0
20
40
Temperature (qC)
60
80
100
D004
Figure 4. Low-side RDSON vs Temperature
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9 Detailed Description
9.1 Overview
The TPS62748 is a high frequency step down converter with ultra low quiescent current. The device operates
with a quasi fixed switching frequency typically at 1.2 MHz. Using TI's DCS-Control™ topology the device
extends the high efficiency operation area down to a few microamperes of load current during Power Save Mode
Operation.
9.2 Functional Block Diagram
CTRL
VOS
EN
Ultra Low Power
Reference VREF = 1.2V
UVLO
Softstart
VOUT
Load Switch
Internal
VFB feedback
divider
network*
VSEL
UVLO
Comp
VIN
UVLO
Auto 100% Mode
Comp
100%
VIN
Mode
Current
Limit Comparator
Timer
VIN
VOUT
Slew Rate
CTRL
Control
EN
UVLO Discharge
LOAD
VTH_100
VTH_UVLO
DCS
Control
VOUT
Discharge
EN
UVLO
Min. On
Limit
High Side
Power Stage
VIN
PMOS
Min. OFF
VOUT
Direct Control
& Compensation
EN
Control
Logic
Gate Driver
Anti
Shoot-Through
SW
VFB
VREF
Error
amplifier
Main
Comparator
Limit
Low Side
Current
Limit Comparator
NMOS
GND
* typical 50MW
9.3 Feature Description
9.3.1 DCS-Control™
TI's DCS-Control™ (Direct Control with Seamless Transition into Power Save Mode) is an advanced regulation
topology, which combines the advantages of hysteretic and voltage mode control. Characteristics of DCSControl™ are excellent AC load regulation and transient response, low output ripple voltage and a seamless
transition between PFM and PWM mode operation. DCS-Control™ includes an AC loop which senses the output
voltage (VOS pin) and directly feeds the information to a fast comparator stage. This comparator sets the
switching frequency, which is constant for steady state operating conditions, and provides immediate response to
dynamic load changes. In order to achieve accurate DC load regulation, a voltage feedback loop is used. The
internally compensated regulation network achieves fast and stable operation with small external components
and low ESR capacitors.
8
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Feature Description (continued)
The DCS-Control™ topology supports PWM (Pulse Width Modulation) mode for medium and high load
conditions and a Power Save Mode at light loads. During PWM mode, it operates in continuous conduction
mode. The switching frequency is typically 1.2 MHz with a controlled frequency variation depending on the input
voltage and load current. If the load current decreases, the converter seamlessly enters Power Save Mode to
maintain high efficiency down to very light loads. In Power Save Mode, the switching frequency varies linearly
with the load current. Since DCS-Control™ supports both operation modes within one single building block, the
transition from PWM to Power Save Mode is seamless with minimum output voltage ripple. The TPS62748 offers
both excellent DC voltage and superior load transient regulation, combined with low output voltage ripple,
minimizing interference with RF circuits.
9.3.2 Power Save Mode Operation
In Power Save Mode the device operates in PFM (Pulse Frequency Modulation) that generates a single
switching pulse to ramp up the inductor current and recharges the output capacitor, followed by a sleep period
where most of the internal circuits are shutdown to achieve lowest operating quiescent current. During this time,
the load current is supported by the output capacitor. The duration of the sleep period depends on the load
current and the inductor peak current. During the sleep periods, the current consumption of TPS62748 is
reduced to 360 nA. This low quiescent current consumption is achieved by an ultra low power voltage reference,
an integrated high impedance feedback divider network and an optimized Power Save Mode operation.
9.3.3 100mA Load Switch
The load switch connects VOS pin to the LOAD pin and is able to support 100 mA. The on-resistance depends
on the output voltage. At 1.2 V Vout the on-resistance is maximum 2.2 Ω and at 1.8 V Vout the on-resistance is
maximum 1.2Ω. The load switch can be used to power a sub system. With CTRL=high the load switch is turned
on. To avoid a voltage drop at the output of the buck converter the load switch has a internal softstart. With
CTRL=low the load switch is turned off and the LOAD pin is internally discharged to GND by typically 30Ω. This
makes sure the output of the load switch is always discharged to GND before the load switch is turned on again.
9.3.4 Output Voltage Selection
The TPS62748 doesn't require an external resistor divider network to program the output voltage. The device
integrates a high impedance feedback resistor divider network which is programmed by the pin VSEL. TPS62748
supports two output voltage options: 1.2 V and 1.8 V. The output voltage is programmed according to Table 1.
The output voltage can be changed during operation and supports a simple dynamic output voltage scaling.
9.3.5 Output Voltage Discharge of the Buck Converter
The device provides automatic output voltage discharge when EN is pulled low or the UVLO is triggered. The
output of the buck converter is discharged over VOS. Because of this the output voltage will ramp up from zero
once the device is enabled again. This is very helpful for accurate start-up sequencing.
9.3.6 Undervoltage Lockout UVLO
To avoid misoperation of the device at low input voltages, an undervoltage lockout is used. The UVLO shuts
down the device at a maximum voltage level of 2.0 V. The device will start at a UVLO level of 2.15 V.
9.3.7 Short circuit protection
The TPS62748 has an integrated current limit on the high side, as well as on the low side MOSFETs. The peak
current in the switch is monitored cycle by cycle and typically limited to 600 mA. The High side MOSFET is
turned off when the typical current limit of 600 mA is reached. The low side MOSFET is turned on when the
current decreases below the low side MOSFET current limit of typically 600 mA.
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9.4 Device Functional Modes
9.4.1 Enable and Shutdown
The device is turned on with EN=high. With EN=low the device enters shutdown and turns off the load switch.
This pin must be terminated.
9.4.2 Device Start-up and Softstart
The device has an internal softstart to minimize input voltage drop during start-up. This allows the operation from
high impedance battery cells. Once the device is enabled the device starts switching after a typical delay time of
10ms. Then the softstart time of typical 700 µs begins with a reduced current limit of typical 150 mA. When this
time passed by the device enters full current limit operation. This allows a smooth start-up and the device can
start into full load current. Furthermore, larger output capacitors impact the start-up behaviour of the DC/DC
converter. Especially when the output voltage does not reach its nominal value after the typical soft-start time of
700 µs, has passed.
9.4.3 Automatic Transition Into No Ripple 100% Mode
Once the input voltage comes close to the output voltage, the DC/DC converter stops switching and enters 100%
duty cycle operation. It connects the output VOUT via the inductor and the internal high side MOSFET switch to
the input VIN, once the input voltage VIN falls below the 100% mode enter threshold, VTH_100-. The DC/DC
regulator is turned off, switching stops and therefore no output voltage ripple is generated. Since the output is
connected to the input, the output voltage follows the input voltage minus the voltage drop across the internal
high side switch and the inductor. Once the input voltage increases and trips the 100% mode exit threshold,
VTH_100+ , the DC/DC regulator turns on and starts switching again. See Figure 5 and Figure 18.
VIN
VIN,
VOUT
100%
Mode
100%
Mode
VTH_100+
VTH_100VOUT
tracks VIN
Step Down Operation
VOUT
tracks VIN
VUVLO+
VUVLOVOUT
discharge
tsoftstart
Figure 5. Automatic Transition into 100% Mode
10
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10 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.
10.1 Application Information
The TPS62748 is a high efficiency step down converter with ultra low quiescent current of typically 360 nA. The
device operates with a tiny 2.2-µH inductor and 10-µF output capacitor over the entire recommended operation
range. A dedicated measurement set-up is required for the light load efficiency measurement and device
quiescent current due to the operation in the sub microampere range. In this range any leakage current in the
measurement set-up will impact the measurement results.
10.2 Typical Application
VIN
2.0V to 5.5V
TPS62748
L 2.2 PH
VOUT
CIN
4.7 PF
VIN
SW
EN
VOS
Low Power
MCU & RF
COUT
10 PF
VSEL
CTRL
GND
Sensor
LOAD
Figure 6. TPS62748 Typical Application Circuit
10.2.1 Design Requirements
The TPS62748 is a highly integrated DC/DC converter. The output voltage is set via a VSEL pin interface. The
design guideline provides a component selection to operate the device within the recommended operating
conditions.
Table 2 shows the list of components for the Application Characteristic Curves
Table 2. Components for Application Characteristic Curves
Reference
Description
TPS62748
360nA Iq step down converter
Value
CIN
Ceramic capacitor, GRM155R61C475ME15
COUT
L
Manufacturer
Texas Instruments
4.7 µF
Murata
Ceramic capacitor, GRM155R60J106ME11
10 µF
Murata
Inductor DFE201610C
2.2 µH
Toko
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10.2.2 Detailed Design Procedure
The first step in the design procedure is the selection of the output filter components. To simplify this process,
Table 3 outlines possible inductor and capacitor value combinations.
Table 3. Recommended LC Output Filter Combinations
Output Capacitor Value [µF] (2)
Inductor Value
[µH] (1)
4.7µF
10µF
22µF
47µF
2.2
√
√ (3)
√
√
(1)
(2)
(3)
100µF
Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.
Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance varies by +20% and –50%.
Typical application configuration. Other check marks indicate alternative filter combinations.
10.2.2.1 Inductor Selection
The inductor value affects the peak-to-peak ripple current, the PWM-to-PFM transition point, the output voltage
ripple and the efficiency. The selected inductor has to be rated for its DC resistance and saturation current. The
inductor ripple current (ΔIL) decreases with higher inductance and increases with higher VIN or VOUT and can be
estimated according to Equation 1.
Equation 2 calculates the maximum inductor current under static load conditions. The saturation current of the
inductor should be rated higher than the maximum inductor current, as calculated with Equation 2. This is
recommended because during a heavy load transient the inductor current rises above the calculated value. A
more conservative way is to select the inductor saturation current according to the high-side MOSFET switch
current limit, ILIMF.
Vout
1Vin
D IL = Vout ´
L ´ ¦
(1)
ILmax = Ioutmax +
DIL
2
where
•
•
•
•
f = Switching Frequency
L = Inductor Value
ΔIL= Peak to Peak inductor ripple current
ILmax = Maximum Inductor current
(2)
The table below shows a list of possible inductors.
Table 4. List of Possible Inductors (1)
(1)
INDUCTANCE [µH]
DIMENSIONS
[mm3]
INDUCTOR TYPE
Isat/DCR
SUPPLIER
Comment
2.2
2.0 x 1.6 x 1.0
DFE201610C
1.4 A/170 mΩ
TOKO
2.2
2.0 × 1.25 × 1.0
MIPSZ2012D 2R2
0.7 A/230 mΩ
FDK
Efficiency plot
Figure 9
2.2
2.0 x 1.2 x 1.0
744 797 752 22
0.7 A/200 mΩ
Würth Elektronik
2.2
1.6 x 0.8 x 0.8
MDT1608CH2R2M
0.7 A/300 mΩ
TOKO
See Third-party Products Disclaimer
10.2.2.2 Output Capacitor Selection
The DCS-Control™ scheme of the TPS62748 allows the use of tiny ceramic capacitors. Ceramic capacitors with
low ESR values have the lowest output voltage ripple and are recommended. The output capacitor requires
either an X7R or X5R dielectric. At light load currents, the converter operates in Power Save Mode and the
output voltage ripple is dependent on the output capacitor value. A larger output capacitors can be used reducing
the output voltage ripple. The leakage current of the output capacitor adds to the overall quiescent current.
12
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10.2.2.3 Input Capacitor Selection
Because the buck converter has a pulsating input current, a low ESR input capacitor is required for best input
voltage filtering to minimize input voltage spikes. For most applications a 4.7-µF input capacitor is sufficient.
When operating from a high impedance source, like a coin cell a larger input buffer capacitor ≥10uF is
recommended avoiding voltage drops during start-up and load transients. The input capacitor can be increased
without any limit for better input voltage filtering. The leakage current of the input capacitor adds to the overall
quiescent current. Table 5 shows a selection of input and output capacitors.
Table 5. List of Possible Capacitors (1)
(1)
CAPACITANCE [μF]
SIZE
CAPACITOR TYPE
SUPPLIER
4.7
0402
GRM155R61C475ME15
Murata
10
0402
GRM155R60J106ME11
Murata
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10.2.3 Application Curves
100%
90%
95%
85%
90%
80%
85%
75%
Efficiency
Efficiency
80%
75%
70%
65%
60%
50%
45%
40%
0.001
0.01
0.1
1
IOUT (mA)
10
100
65%
60%
55%
VIN = 2.5 V
VIN = 3.0 V
VIN = 3.6 V
VIN = 4.2 V
VIN = 5.0 V
55%
70%
45%
40%
0.001
1000
1600
90%
1400
Switching Frequency (kHz)
85%
Efficiency
80%
75%
70%
65%
DEF201610
MIPSZ2012
WE 744 797 752 22
MDT1608
50%
0.001
0.1
1
IOUT (mA)
10
100
1000
D009
Figure 8. Efficiency vs Load Current; VOUT = 1.2 V
95%
55%
0.01
D008
Figure 7. Efficiency vs Load Current; VOUT = 1.8 V
60%
VIN = 2.5 V
VIN = 3.0 V
VIN = 3.6 V
VIN = 4.2 V
VIN = 5.0 V
50%
1200
1000
800
VIN = 5.0 V
VIN = 3.6 V
VIN = 3.0 V
VIN = 2.2 V
600
400
200
0
0.01
0.1
1
IOUT (mA)
10
100
1000
0
50
D010
Figure 9. Efficiency vs Load Current; VOUT = 1.8 V
100
150
200
IOUT (mA)
250
300
350
D012
Figure 10. Switching Frequency vs Load Current
VOUT = 1.8 V
1400
Switching Frequency (kHz)
1200
1000
800
600
400
VIN = 5.0 V
VIN = 3.6 V
VIN = 3.0 V
VIN = 2.0 V
200
0
0
50
100
150
200
IOUT (mA)
250
300
350
D013
Figure 11. Switching Frequency vs Load Current
VOUT = 1.2 V
14
Figure 12. PFM (Power Save Mode) Mode Operation
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IL
Figure 14. Startup Into 100 mA Electronic Load
EN Delay + Soft-Start Delay
Figure 13. PWM Mode Operation
IL
IL
Figure 15. Startup Into 300 mA Electronic Load
Soft-Start Delay
Figure 16. Load Transient Response; 100 mA to 290 mA
IL
Figure 17. Load Transient Response; 5 mA to 290 mA
Figure 18. 100% Mode Entry and Leave Operation
IOUT = 30 mA
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10.3 System Example
Temperature
Sensor
Electronic
Compass
3-Axis Sensor
Radio
VIN
2.0V to 5.5V
CIN
4.7 PF
TPS62748
VIN
SW
EN
VOS
VSEL
L 2.2 PH
VOUT = 1.8V
Main Rail
COUT
10 PF
MCU
CTRL
GND
LOAD
Sensor
Figure 19. Example Of Implementation In A Master MCU Based System
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11 Power Supply Recommendations
The power supply must provide a current rating according to the supply voltage, output voltage and output
current of the TPS62748.
12 Layout
12.1 Layout Guidelines
•
•
•
•
As for all switching power supplies, the layout is an important step in the design. Care must be taken in board
layout to get the specified performance.
It is critical to provide a low inductance, impedance ground path. Therefore, use wide and short traces for the
main current paths.
The input capacitor should be placed as close as possible to the IC pins VIN and GND. This is the most
critical component placement.
The VOS line is a sensitive high impedance line and should be connected to the output capacitor and routed
away from noisy components and traces (e.g. SW line) or other noise sources.
12.2 Layout Example
VOUT
GND
COUT
L
CIN
VIN
Figure 20. Recommended PCB Layout
12.3 Package Dimensions
D: Max=1.592 mm, Min=1.532 mm
E: Max=0.896 mm, Min=0.836 mm
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13 Device and Documentation Support
13.1 Device Support
13.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
13.2 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.
13.3 Trademarks
DCS-Control, E2E are trademarks of Texas Instruments.
Bluetooth is a registered trademark of Bluetooth SIG, Inc.
All other trademarks are the property of their respective owners.
13.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
13.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
14 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.
18
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PACKAGE OPTION ADDENDUM
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20-Oct-2015
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)
TPS62748YFPR
ACTIVE
DSBGA
YFP
8
3000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 125
TPS748
TPS62748YFPT
ACTIVE
DSBGA
YFP
8
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 125
TPS748
(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)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(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.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
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20-Oct-2015
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 2
D: Max = 1.592 mm, Min =1.531 mm
E: Max = 0.896 mm, Min =0.836 mm
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