TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
TM
4.5V to 18V Input, 2-A Synchronous Step-Down SWIFT Converter
Check for Samples: TPS54225-Q1
FEATURES
1
•
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23
•
•
•
•
•
•
•
•
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Qualified for Automotive Applications
D-CAP2™ Mode Enables Fast Transient
Response
Low Output Ripple and Allows Ceramic Output
Capacitor
Wide VCC Input Voltage Range: 4.5 V to 18 V
Wide VIN Input Voltage Range: 2 V to 18 V
Output Voltage Range: 0.76 V to 5.5 V
Highly Efficient Integrated FET’s Optimized
for Lower Duty Cycle Applications
- 160 mΩ (High Side) and 110 mΩ (Low Side)
High Efficiency, less than 10 μA at shutdown
High Initial Bandgap Reference Accuracy
Adjustable Soft Start
Pre-Biased Soft Start
700-kHz Switching Frequency (fSW)
Cycle-By-Cycle Overcurrent Limit
Power Good Output
APPLICATIONS
DESCRIPTION
The TPS54225-Q1 is an adaptive on-time D-CAP2™
mode
synchronous
buck
converter.
The
TPS54225-Q1 enables system designers to complete
the suite of various end equipment’s power bus
regulators with a cost effective, low component count,
low standby current solution. The main control loop
for the TPS54225-Q1 uses the D-CAP2™ mode
control which provides a fast transient response with
no external compensation components.
The TPS54225-Q1 also has a proprietary circuit that
enables the device to adapt to both low equivalent
series resistance (ESR) output capacitors, such as
POSCAP or SP-CAP, and ultra-low ESR ceramic
capacitors. The device operates from 4.5-V to 18-V
VCC input , and from 2-V to 18-V VIN input power
supply voltage. The output voltage can be
programmed between 0.76 V and 5.5 V. The device
also features an adjustable slow start time and a
power good function. The TPS54225-Q1 is available
in the 14 pin HTSSOP package, and designed to
operate from –40°C to 85°C.
•
Wide Range of Applications for Low Voltage
System
– Digital TV Power Supply
– High Definition Blu-ray Disc™ Players
– Networking Home Terminal
– Digital Set Top Box (STB)
space
VOUT (50 mV/div)
IOUT (1 A/div)
100 ms/div
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
D-CAP2, PowerPAD are trademarks of Texas Instruments.
Blu-ray Disc is a trademark of Blu-ray Disc Association.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
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.
ORDERING INFORMATION (1)
TA
PACKAGE
–40°C to 105°C
(1)
(2)
(3)
(2) (3)
PowerPAD™
(HTSSOP) – PWP (14 Pins)
ORDERABLE PART NUMBER
TOP-SIDE MARKING
TPS54225TPWPRQ1
54225Q1
Tape and Reel
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
Package drawings, thermal data, and symbolization are available at www.ti.com/packaging.
All package options have Cu NIPDAU lead/ball finish.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)
(1)
VALUE
UNIT
–0.3 to 20
V
VBST
–0.3 to 26
V
VBST (vs SW1, SW2)
–0.3 to 6.5
V
VFB, VO, SS, PG
–0.3 to 6.5
V
–2 to 20
V
VIN, VCC, EN
VI
Input voltage range
SW1, SW2
–3 to 20
V
VREG5
–0.3 to 6.5
V
PGND1, PGND2
–0.3 to 0.3
V
SW1, SW2 (10 ns transient)
VO
Output voltage range
Vdiff
Voltage from GND to POWERPAD
ESD rating Electrostatic discharge
–0.2 to 0.2
V
Human Body Model (HBM)
2
kV
Charged Device Model (CDM)
1
kV
TJ
Operating junction temperature
–40 to 150
°C
Tstg
Storage temperature
–55 to 150
°C
(1)
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.
THERMAL INFORMATION
TPS54225-Q1
THERMAL METRIC (1)
PWP
UNITS
14 PINS
θJA
Junction-to-ambient thermal resistance
55.6
θJCtop
Junction-to-case (top) thermal resistance
51.3
θJB
Junction-to-board thermal resistance
26.4
ψJT
Junction-to-top characterization parameter
1.8
ψJB
Junction-to-board characterization parameter
20.6
θJCbot
Junction-to-case (bottom) thermal resistance
4.3
(1)
2
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
RECOMMENDED OPERATING CONDITIONS
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
VCC
Supply input voltage range
4.5
18
V
VIN
Power input voltage range
2
18
V
VBST
–0.1
24
VBST (vs SW1, SW2)
–0.1
5.7
SS, PG
–0.1
5.7
EN
–0.1
18
VO, VFB
–0.1
5.5
SW1, SW2
–1.8
18
VI
Input voltage range
–3
18
PGND1, PGND2
–0.1
0.1
SW1, SW2 (10 ns transient)
V
VO
Output voltage range
VREG5
–0.1
5.7
V
IO
Output current range
IVREG5
0
10
mA
TA
Operating free-air temperature
–40
105
°C
TJ
Operating junction temperature
–40
125
°C
TYP
MAX
UNIT
ELECTRICAL CHARACTERISTICS
over operating free-air temperature range, VCC, VIN = 12V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
SUPPLY CURRENT
IVCC
Operating - non-switching supply
current
VCC current, TA = 25°C, EN = 5 V,
VFB = 0.8 V
800
1200
μA
IVCCSDN
Shutdown supply current
VCC current, TA = 25°C, EN = 0 V
1.8
10
μA
LOGIC THRESHOLD
VENH
EN high-level input voltage
EN
VENL
EN low-level input voltage
EN
2
V
0.4
V
VFB VOLTAGE AND DISCHARGE RESISTANCE
VFB
Threshold voltage
TA = 25°C, VO = 1.05 V
757
TA = 0°C to 85°C, VO = 1.05 V (1)
753
777
TA = -40°C to 85°C, VO = 1.05 V (1)
751
780
IVFB
Input current
VFB = 0.8 V, TA = 25°C
RDischg
VO discharge resistance
EN = 0 V, VO = 0.5 V, TA = 25°C
765
773
mV
0
±0.1
μA
50
100
Ω
5.5
5.7
V
20
mV
100
mV
VREG5 OUTPUT
VVREG5
Output voltage
TA = 25°C, 6 V < VCC < 18 V,
0 < IVREG5 < 5 mA
VLN5
Line regulation
6 V < VCC < 18 V, IVREG5 = 5 mA
VLD5
Load regulation
0 mA < IVREG5 < 5 mA
IVREG5
Output current
VCC = 6 V, VREG5 = 4 V, TA = 25°C
RDS(on)h
High side switch resistance
RDS(on)l
Low side switch resistance
5.3
70
mA
25°C, VBST - SW1, SW2 = 5.5 V
160
mΩ
25°C
110
mΩ
MOSFET
CURRENT LIMIT
Iocl
Current limit
LOUT = 2.2µH
(1)
2.5
3.1
4.5
A
THERMAL SHUTDOWN
TSDN
(1)
Thermal shutdown threshold
Shutdown temperature
Hysteresis
(1)
(1)
150
25
°C
Specified by Design (not production tested).
Copyright © 2011, Texas Instruments Incorporated
3
TPS54225-Q1
SLVSAV9 – JUNE 2011
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ELECTRICAL CHARACTERISTICS (continued)
over operating free-air temperature range, VCC, VIN = 12V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ON-TIME TIMER CONTROL
tON
On time
VIN = 12 V, VO = 1.05 V
145
tOFF(MIN)
Minimum off time
TA = 25°C, VFB = 0.7 V
260
310
ns
2.6
ns
SOFT START
ISSC
Charge current
VSS = 0 V
1.4
2
ISSD
Discharge current
VSS = 0.5 V
0.1
0.2
VFB rising (good)
85
90
μA
mA
POWER GOOD
VTHPG
Threshold
IPG
Sink current
VFB falling (fault)
PG = 0.5 V
95
85
2.5
5
115
120
%
mA
OUTPUT UNDERVOLTAGE AND OVERVOLTAGE PROTECTION
VOVP
Output OVP trip threshold
tOVPDEL
Output OVP prop delay
VUVP
Output UVP trip threshold
tUVPDEL
Output UVP delay
tUVPEN
Output UVP enable delay
OVP detect
125
UVP detect
65
Hysteresis
70
75
10
0.25
Relative to soft-start time
%
μs
5
%
ms
x 1.7
UVLO
UVLO
4
UVLO threshold
Wake up VREG5 voltage
3.55
3.8
4.05
Hysteresis VREG5 voltage
0.23
0.35
0.47
V
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
DEVICE INFORMATION
PWP PACKAGE
(TOP VIEW)
1
VO
2
VFB
3
VREG5
VCC
14
VIN
13
VBST
12
SW2
11
POWER PAD
4
SS
5
GND
6
PG
PGND2
9
7
EN
PGND1
8
SW1 10
PIN FUNCTIONS
PIN
NAME
NO.
DESCRIPTION
VO
1
Connect to output of converter. This pin is used for On-Time Adjustment.
VFB
2
Converter feedback input. Connect with feedback resistor divider.
VREG5
3
5.5 V power supply output. A capacitor (typical 1μF) should be connected to GND.
SS
4
Soft-start control. A external capacitor should be connected to GND.
GND
5
Signal ground pin
PG
6
Open drain power good output
EN
7
Enable control input
PGND1, PGND2
SW1, SW2
8, 9
10, 11
Ground returns for low-side MOSFET. Also serve as inputs of current comparators. Connect PGND and
GND strongly together near the IC.
Switch node connection between high-side NFET and low-side NFET. Also serve as inputs to current
comparators.
VBST
12
Supply input for high-side NFET gate driver (boost terminal). Connect capacitor from this pin to
respective SW1, SW2 terminals. An internal PN diode is connected between VREG5 to VBST pin.
VIN
13
Power input and connected to high side NFET drain
VCC
14
Supply input for 5 V internal linear regulator for the control circuitry
PowerPAD™
Back side
Thermal pad of the package. Must be soldered to achieve appropriate dissipation. Should be connected
to PGND.
Copyright © 2011, Texas Instruments Incorporated
5
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
Functional Block Diagram
-30%
UV
14
VO
VIN
VIN
OV
1
VCC
13
+20%
VREG5
12
Control logic
VBST
Ref
SS
1 shot
SW
VFB
SGND
10
XCON
VREG5
VREG5
Ceramic
Capacitor
3
1mF
VO
11
2
SS
9
4
8
SW
Softstart
ZC
SS
PGND
5
PGND
PGND
GND
SW
OCP
SGND
PG
Ref
6
PGND
VCC
-10%
UV
VREG5
EN
7
EN
Logic
OV
UVLO
UVLO
Protection
Logic
TSD
REF
Ref
OVERVIEW
The TPS54225-Q1 is a 2-A synchronous step-down (buck) converter with two integrated N-channel MOSFETs. It
operates using D-CAP2™ mode control. The fast transient response of D-CAP2™ control reduces the output
capacitance required to meet a specific level of performance. Proprietary internal circuitry allows the use of low
ESR output capacitors including ceramic and special polymer types.
DETAILED DESCRIPTION
PWM Operation
The main control loop of the TPS54225-Q1 is an adaptive on-time pulse width modulation (PWM) controller that
supports a proprietary D-CAP2™ mode control. D-CAP2™ mode control combines constant on-time control with
an internal compensation circuit for pseudo-fixed frequency and low external component count configuration with
both low ESR and ceramic output capacitors. It is stable even with virtually no ripple at the output.
At the beginning of each cycle, the high-side MOSFET is turned on. This MOSFET is turned off after internal one
6
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
www.ti.com
SLVSAV9 – JUNE 2011
shot timer expires. This one shot timer is set by the converter input voltage ,VIN, and the output voltage ,VO, to
maintain a pseudo-fixed frequency over the input voltage range, hence it is called adaptive on-time control. The
one-shot timer is reset and the high-side MOSFET is turned on again when the feedback voltage falls below the
reference voltage. An internal ramp is added to the reference voltage to simulate output ripple, eliminating the
need for ESR induced output ripple from D-CAP2™ mode control.
PWM Frequency and Adaptive On-Time Control
TPS54225-Q1 uses an adaptive on-time control scheme and does not have a dedicated on board oscillator. The
TPS54225-Q1 runs with a pseudo-constant frequency of 700 kHz by using the input voltage and output voltage
to set the on-time one-shot timer. The on-time is inversely proportional to the input voltage and proportional to
the output voltage. The actual frequency may vary from 700 kHz depending on the off time, which is ended when
the fed back portion of the output voltage falls to the VFBthreshold voltage.
Soft Start and Pre-Biased Soft Start
The soft start function is adjustable. When the EN pin becomes high, 2-μA current begins charging the capacitor
which is connected from the SS pin to GND. Smooth control of the output voltage is maintained during start up.
The equation for the slow start time is shown in Equation 1. VFB voltage is 0.765 V and SS pin source current is
2 μA.
C6(nF) • Vref
C6(nF) • 0.765
Tss(ms) = − = −
Iss(µA)
2
(1)
A unique circuit to prevent current from being pulled from the output during startup if the output is pre-biased.
When the soft-start commands a voltage higher than the pre-bias level (internal soft start becomes greater than
feedback voltage VFB), the controller slowly activates synchronous rectification by starting the first low side FET
gate driver pulses with a narrow on-time. It then increments that on-time on a cycle-by-cycle basis until it
coincides with the time dictated by (1-D), where D is the duty cycle of the converter. This scheme prevents the
initial sinking of the pre-bias output, and ensure that the out voltage (VO) starts and ramps up smoothly into
regulation and the control loop is given time to transition from pre-biased start-up to normal mode operation.
Power Good
The power good function is activated after soft start has finished. The power good function becomes active after
1.7 times soft-start time. When the output voltage is within –10% of the target value, internal comparators detect
power good state and the power good signal becomes high. Rpg resister value, which is connected between PG
and VREG5, is required from 20 kΩ to 150 kΩ. If the feedback voltage goes under 15% of the target value, the
power good signal becomes low after a 10 ms internal delay.
Output Discharge Control
The TPS54225-Q1 discharges the output when EN is low, or the controller is turned off by the protection
functions (OVP, UVP, UVLO and thermal shutdown). The output is discharged by an internal 50-Ω MOSFET
which is connected from VO to PGND. The internal low-side MOSFET is not turned on during the output
discharge operation to avoid the possibility of causing negative voltage at the output.
Current Protection
The output over-current protection (OCP) is implemented using a cycle-by-cycle valley detect control circuit. The
switch current is monitored by measuring the low-side FET switch voltage between the SW pin and GND. This
voltage is proportional to the switch current. To improve accuracy, the voltage sensing is temperature
compensated.
During the on time of the high-side FET switch, the switch current increases at a linear rate determined by Vin,
Vout, the on-time, and the output inductor value. During the on time of the low-side FET switch, this current
decreases linearly. The average value of the switch current is the load current Iout. If the measured voltage is
above the voltage proportional to the current limit, then the device constantly monitors the low-side FET switch
voltage, which is proportional to the switch current, during the low-side on-time.
The converter maintains the low-side switch on until the measured voltage is below the voltage corresponding to
the current limit at which time the switching cycle is terminated and a new switching cycle begins. In subsequent
switching cycles, the on-time is set to a fixed value and the current is monitored in the same manner.
Copyright © 2011, Texas Instruments Incorporated
7
TPS54225-Q1
SLVSAV9 – JUNE 2011
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There are some important considerations for this type of over-current protection. The load current one half of the
peak-to-peak inductor current higher than the over-current threshold. Also when the current is being limited, the
output voltage tends to fall as the demanded load current may be higher than the current available from the
converter. This may cause the output under-voltage protection circuit to be activated. When the over current
condition is removed, the output voltage will return to the regulated value. This protection is non-latching.
Over/Undervoltage Protection
The TPS54225-Q1 detects over and undervoltage conditions by monitoring the feedback voltage (VFB). This
function is enabled after approximately 1.7 times the soft-start time.When the feedback voltage becomes higher
than 120% of the target voltage, the OVP comparator output goes high and the circuit latches the high-side
MOSFET driver turns off and the low-side MOSFET turns on. When the feedback voltage becomes lower than
70% of the target voltage, the UVP comparator output goes high and an internal UVP delay counter begins. After
250 μs, the device latches off both internal top and bottom MOSFET.
UVLO Protection
Undervoltage lock out protection (UVLO) monitors the voltage of the VREG5 pin. When the VREG5 voltage is lower
than UVLO threshold voltage, the TPS54225-Q1 is shut off. This is protection is non-latching.
Thermal Shutdown
Thermal protection is self-activating. If the junction temperature exceeds the threshold value (typically 150°C),
the TPS54225-Q1 shuts off. This protection is non-latching.
8
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
TYPICAL CHARACTERISTICS
VCC TEMPERATURE
vs
JUNCTION TEMPERATURE
VCC SHUTDOWN CURRENT
vs
JUNCTION TEMPERATURE
1200
8
IVCCSDN - Shutdown Current - mA
IVCC Supply Current - mA
1000
800
600
400
200
0
-50
0
50
100
TJ - Junction Temperature - °C
6
4
2
0
-50
150
0
50
100
TJ - Junction Temperature - °C
Figure 1.
Figure 2.
EN CURRENT
vs
EN VOLTAGE
1.05-V OUTPUT VOLTAGE
vs
OUTPUT CURRENT
100
150
1.1
VOUT - Output Voltage - V
EN Input Current - mA
80
60
40
1.075
VI = 18 V
1.05
VI = 12 V
VI = 5.5 V
1.025
20
0
0
5
10
15
EN Input Voltage - V
Figure 3.
Copyright © 2011, Texas Instruments Incorporated
20
1
0
0.5
1
1.5
Iout - Output Current - A
2
Figure 4.
9
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SLVSAV9 – JUNE 2011
www.ti.com
TYPICAL CHARACTERISTICS (continued)
1.05-V OUTPUT VOLTAGE
vs
INPUT VOLTAGE
1.05-V, 0-A TO 2-A-LOAD TRANSIENT RESPONSE
1.1
VOUT - Output Voltage - V
VOUT - 50 mV/div
1.075
IO = 0 A
1.05
IO = 1 A
IOUT - 2 A/div
1.025
100 ms/div
1
0
5
10
15
VIN - Input Voltage - V
20
Figure 5.
Figure 6.
START-UP WAVEFORM
EFFICIENCY
vs
OUTPUT CURRENT
100
VO = 3.3 V
EN - 10 V/div
90
VO = 2.5 V
Efficiency - %
80
VOUT - 0.5 V/div
VO = 1.8 V
70
60
PG - 5 V/div
50
400 ms/div
Figure 7.
10
40
0
0.5
1
1.5
IOUT - Output Current - A
2
Figure 8.
Copyright © 2011, Texas Instruments Incorporated
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SLVSAV9 – JUNE 2011
www.ti.com
TYPICAL CHARACTERISTICS (continued)
SWITCHING FREQUENCY
vs
INPUT VOLTAGE
SWITCHING FREQUENCY
vs
OUTPUT CURRENT
900
fsw - Switching Frequency - kHz
fsw - Switching Frequency - kHz
900
800
VO = 1.8 V
700
600
VO = 3.3 V
800
VO = 1.8 V
700
VO = 3.3 V
600
500
500
0
5
10
15
VIN - Input Voltage - V
20
0
0.5
1
1.5
IO - Output Current - A
Figure 9.
Figure 10.
VOLTAGE RIPPLE AT OUTPUT
VOLTAGE RIPPLE AT INPUT
2
VO = 1.05 V
VO = 1.05 V
VIN - 50 mV/div
VO - 10 mV/div
SW - 5 V/div
Figure 11.
Copyright © 2011, Texas Instruments Incorporated
SW - 5 V/div
Figure 12.
11
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SLVSAV9 – JUNE 2011
www.ti.com
DESIGN GUIDE
Step By Step Design Procedure
To
•
•
•
•
•
begin the design process, the following application parameters must be known:
Input voltage range
Output voltage
Output current
Output voltage ripple
Input voltage ripple
VIN
4.5 to 18V
U1
TPS542225PWP
14
13
1
2
4
7
VCC
SW1
VIN
SW2
VO
VBST
VFB
PG
SS
VREG5
EN
PGND1
5 GND
10
VOUT
1.05V, 2A
11
12
6
3
8
PGND2 9
PwPd
15
Figure 13. Schematic Diagram
Output Voltage Resistors Selection
The output voltage is set with a resistor divider from the output node to the VFB pin. It is recommended to use
1% tolerance or better divider resistors. Start by using Equation 2 and Equation 3 to calculate VOUT.
To improve efficiency at light loads consider using larger value resistors, too high of resistance is more
susceptible to noise and voltage errors from the VFB input current is more noticeable.
For output voltage from 0.76 V to 2.5 V:
R1
VOUT = 0.765 • 1 + −
R2
(
)
(2)
For output voltage over 2.5 V:
R1
VOUT = (0.763 + 0.0017 • VOUT) • 1 + −
R2
(
)
(3)
Where:
VOUT_SET = Target VOUT voltage
Output Filter Selection
The output filter used with the TPS54225-Q1 is an LC circuit. This LC filter has double pole at:
FP =
12
1
2p LOUT ´ COUT
(4)
Copyright © 2011, Texas Instruments Incorporated
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SLVSAV9 – JUNE 2011
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At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54225-Q1. The low frequency phase is 180 degrees. At the output filter pole frequency, the gain
rolls off at a -40 dB per decade rate and the phase drops rapidly. D-CAP2™ introduces a high frequency zero
that reduces the gain roll off to -20 dB per decade and increases the phase to 90 degrees one decade above the
zero frequency. The inductor and capacitor selected for the output filter must be selected so that the double pole
of Equation 4 is located below the high frequency zero but close enough that the phase boost provided be the
high frequency zero provides adequate phase margin for a stable circuit. To meet this requirement use the
values recommended in Table 1.
Table 1. Recommended Component Values
OUTPUT VOLTAGE
(V)
R1 (kΩ)
R2 (kΩ)
1
6.81
1.05
1.2
(1)
C4 (pF) (1)
L1 (µH)
C8 + C9 (µF)
22.1
2.2
22 - 68
8.25
22.1
2.2
22 - 68
12.7
22.1
2.2
22 - 68
1.8
30.1
22.1
10 - 47
3.3
22 - 68
2.5
49.9
22.1
10 - 47
3.3
22 - 68
3.3
73.2
22.1
10 - 47
3.3
22 - 68
5
121
22.1
10 - 47
4.7
22 - 68
Optional
For higher output voltages at or above 1.8 V, additional phase boost can be achieved by adding a feed forward
capacitor (C4) in parallel with R1.
The inductor peak-to-peak ripple current, peak current, and RMS current are calculated using Equation 5,
Equation 6, and Equation 7. The inductor saturation current rating must be greater than the calculated peak
current and the RMS or heating current rating must be greater than the calculated RMS current. Use 700 kHz for
fSW.
Make sure the chosen inductor is rated for the peak current of Equation 6 and the RMS current of Equation 7.
VOUT VIN (max) - VOUT
• 
Ilp - p = V
L •f
IN (max)
O
SW
Ilp - p
Ilpeak = IO + 
2
−
1 Ilp - p2
ILo(RMS) = IO2 + −
12
√
(5)
(6)
(7)
For this design example, the calculated peak current is 2.23 A and the calculated RMS current is 2.01 A. The
inductor used is a TDK SPM6530-2R2M100 with a peak current rating of 11.5 A and an RMS current rating of 11
A.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54225-Q1 is intended for
use with ceramic or other low ESR capacitors. Recommended values range from 22 µF to 68 µF. Use Equation 8
to determine the required RMS current rating for the output capacitor.
VOUT • (VIN - VOUT)
ICO(RMS) =−
−
√12 • VIN • LO • fSW
(8)
For this design two TDK C3216X5R0J226M 22 µF output capacitors are used. The typical ESR is 2 mΩ each.
The calculated RMS current is 0.271 A and each output capacitor is rated for 4 A.
Input Capacitor Selection
The TPS54225-Q1 requires an input decoupling capacitor and a bulk capacitor is needed depending on the
application. A ceramic capacitor over 10 μF is recommended for the decoupling capacitor. An additional 0.1 µF
capacitor from pin 14 to ground is recommended to improve the stability of the over-current limit function. The
capacitor voltage rating needs to be greater than the maximum input voltage.
Copyright © 2011, Texas Instruments Incorporated
13
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
Bootstrap Capacitor Selection
A 0.1 µF ceramic capacitor must be connected between the VBST to SW pin for proper operation. It is
recommended to use a ceramic capacitor.
VREG5 Capacitor Selection
A 1.0 µF ceramic capacitor must be connected between the VREG5 to GND pin for proper operation. It is
recommended to use a ceramic capacitor.
THERMAL INFORMATION
This PowerPAD™ package incorporates an exposed thermal pad that is designed to be connected to an external
heatsink. The thermal pad must be soldered directly to the printed board (PCB). After soldering, the PCB can be
used as a heatsink. In addition, through the use of thermal vias, the thermal pad can be attached directly to the
appropriate copper plane shown in the electrical schematic for the device, or alternatively, can be attached to a
special heatsink structure designed into the PCB. This design optimizes the heat transfer from the integrated
circuit (IC).
For additional information on the PowerPAD™ package and how to use the advantage of its heat dissipating
abilities, refer to Technical Breif, PowerPAD™ Thermally Enhanced Package, Texas Instruments Literature No.
SLMA002 and Application Brief, PowerPAD™ Made Easy, Texas Instruments Literature No. SLMA004.
The exposed thermal pad dimensions for this package are shown in the following illustration.
8
14
Thermal Pad
2.46
°
7
1
2.31
Figure 14. Thermal Pad Dimensions
14
Copyright © 2011, Texas Instruments Incorporated
TPS54225-Q1
SLVSAV9 – JUNE 2011
www.ti.com
LAYOUT CONSIDERATIONS
1. Keep the input switching current loop as small as possible.
2. Keep the SW node as physically small and short as possible to minimize parasitic capacitance and
inductance and to minimize radiated emissions. Kelvin connections should be brought from the output to the
feedback pin of the device.
3. Keep analog and non-switching components away from switching components.
4. Make a single point connection from the signal ground to power ground.
5. Do not allow switching current to flow under the device.
6. Keep the pattern lines for VIN and PGND broad.
7. Exposed pad of device must be connected to PGND with solder.
8. VREG5 capacitor should be placed near the device, and connected PGND.
9. Output capacitor should be connected to a broad pattern of the PGND.
10. Voltage feedback loop should be as short as possible, and preferably with ground shield.
11. Lower resistor of the voltage divider which is connected to the VFB pin should be tied to SGND.
12. Providing sufficient via is preferable for VIN, SW and PGND connection.
13. PCB pattern for VIN, SW, and PGND should be as broad as possible.
14. If VIN and VCC is shorted, VIN and VCC patterns need to be connected with broad pattern lines.
15. VIN Capacitor should be placed as near as possible to the device.
Additional
Thermal
Vias
FEEDBACK
RESISTORS
VCC
INPUT
BYPASS
CAPACITOR
VCC
VCC
VOUT
BIAS
CAP
VFB
VIN
VREG5
VBST
SS
SW1
GND
Connection to
POWER GROUND
on internal or
bottom layer
SLOW
START
CAP
ANALOG
GROUND
TRACE
PG
EN
VIN
VIN
INPUT
BYPASS
CAPACITOR
SW2
PGND1
EXPOSED
POWERPAD
AREA
BOOST
CAPACITOR
OUTPUT
INDUCTOR
PGND2
VOUT
OUTPUT
FILTER
CAPACITOR
Additional
Thermal
Vias
To Enable
Control
POWER GROUND
VIA to Ground Plane
Etch on Bottom Layer
or Under Component
Figure 15. TPS54225-Q1 Layout
Copyright © 2011, Texas Instruments Incorporated
15
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
TPS54225TPWPRQ1
ACTIVE
Package Type Package Pins Package
Drawing
Qty
HTSSOP
PWP
14
2000
Eco Plan
Lead/Ball Finish
(2)
Green (RoHS
& no Sb/Br)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
CU NIPDAU
Level-3-260C-168 HR
(4)
-40 to 105
54225Q1
(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)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side 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 Top-Side Marking for that device.
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.
OTHER QUALIFIED VERSIONS OF TPS54225-Q1 :
• Catalog: TPS54225
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
NOTE: Qualified Version Definitions:
• Catalog - TI's standard catalog product
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Jul-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
TPS54225TPWPRQ1
Package Package Pins
Type Drawing
SPQ
HTSSOP
2000
PWP
14
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
330.0
12.4
Pack Materials-Page 1
6.9
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
14-Jul-2012
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
TPS54225TPWPRQ1
HTSSOP
PWP
14
2000
367.0
367.0
35.0
Pack Materials-Page 2
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