TPS54380-Q1
SLVS836 − JUNE 2008
3-V TO 6-V INPUT, 3-A OUTPUT TRACKING SYNCHRONOUS BUCK
PWM SWITCHER WITH INTEGRATED FETs (SWIFT) FOR SEQUENCING
6,4 mm X 6,6 mm
Typical Size
FEATURES
DQualified for Automotive Applications
DPower-Up/Down Tracking for Sequencing
D60-mΩ MOSFET Switches for High Efficiency
at 3-A Continuous Output Source or Sink
Current
DWide PWM Frequency:
Fixed 350 kHz or Adjustable 280 kHz to
700 kHz
DPower Good and Enable
DLoad Protected by Peak Current Limit and
Thermal Shutdown
DIntegrated Solution Reduces Board Area and
Component Count
APPLICATIONS
DLow-Voltage, High-Density Distributed Power
Systems
DPoint of Load Regulation for
High-Performance DSPs, FPGAs, ASICs, and
Microprocessors Requiring Sequencing
DBroadband, Networking, and Optical
Communications Infrastructure
DESCRIPTION
As a member of the SWIFT family of dc/dc regulators,
the TPS54380 low-input voltage, high-output current,
synchronous buck PWM converter integrates all
required active components. Using the TRACKIN pin
with other regulators, simultaneous power up and down
are easily implemented. Included on the substrate with
the listed features are a true, high-performance, voltage
error amplifier that enables maximum performance and
flexibility in choosing the output filter L and C
components; an undervoltage-lockout circuit to prevent
start-up until the input voltage reaches 3 V; an internally
or externally set slow-start circuit to limit inrush
currents; and a power-good output useful for
processor/logic reset.
The TPS54380 is available in a thermally enhanced
20-pin TSSOP (PWP) PowerPAD package, which
eliminates bulky heatsinks. TI provides evaluation
modules and the SWIFT designer software tool to aid
in quickly achieving high-performance power supply
designs to meet aggressive equipment development
cycles.
SIMPLIFIED SCHEMATIC
VIN PH
BOOT
PGND
VSENSE
Core Supply
COMPAGND
VBIAS
Input
TPS54380
TRACKIN
I/O Supply
VI/O = 3.3 V
Vcore = 1.8 V
RL = 1 Ω
START-UP WAVEFORM
1 ms/div
500 mV/div
PRODUCTION DATA information is current as of publication date. Products
conform to specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
PowerPAD and SWIFT are trademarks of Texas Instruments.
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.
www.ti.com
Copyright 2008, Texas Instruments Incorporated
TPS54380-Q1
SLVS836 − JUNE 2008
www.ti.com
2
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.
ORDERING INFORMATION(1)
TJPACKAGE(2) ORDERABLE PART NUMBER TOP-SIDE MARKING
−40°C to 125°CHTSSOP − PW Reel of 2000 TPS54380QPWPRQ1 54380Q
(1) 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 http://www.ti.com.
(2)) Package drawings, thermal data, and symbolization are available at http://www.ti.com/packaging.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted(1)
VIN, ENA −0.3 V to 7 V
Itlt V
RT −0.3 V to 6 V
Input voltage range, VIVSENSE, TRACKIN −0.3 V to 4 V
BOOT −0.3 V to 17 V
Ot t lt V
VBIAS, COMP, PWRGD −0.3 V to 7 V
Output voltage range, VOPH −0.6 V to 10 V
StI
PH Internally Limited
Source current, IOCOMP, VBIAS 6 mA
PH 6 A
Sink current, ISCOMP 6 mA
Sink
current,
IS
ENA, PWRGD 10 mA
Voltage differential AGND to PGND ±0.3 V
Operating virtual-junction temperature range, TJ−40°C to 125°C
Storage temperature, Tstg −65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 300°C
Human-Body Model (HBM) 2000 V
Electrostatic discharge protection, ESD Charged-Device Model (CDM) 1500 V
(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.
RECOMMENDED OPERATING CONDITIONS
MIN MAX UNIT
Input voltage, VI3 6 V
Operating junction temperature, TJ−40 125 °C
DISSIPATION RATINGS(1)(2)
PACKAGE THERMAL IMPEDANCE
JUNCTION-TO-AMBIENT
TA =25°C
POWER RATING
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
20-pin PWP with solder 26 °C/W 3.85 W(3) 2.12 W 1.54 W
20-pin PWP without solder 57.5 °C/W 1.73 W 0.96 W 0.69 W
(1) For more information on the PWP package, see TI technical brief, literature number SLMA002.
(2) Test board conditions:
1. 3-in x 3-in, two layers, thickness: 0.062 in
2. 1.5-oz copper traces located on the top of the PCB
3. 1.5-oz copper ground plane on the bottom of the PCB
4. 10 thermal vias (see “Recommended Land Pattern” in applications section of this data sheet)
(3) Maximum power dissipation may be limited by overcurrent protection.
TPS54380-Q1
SLVS836 − JUNE 2008
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3
ELECTRICAL CHARACTERISTICS
over operating free-air temperature range unless otherwise noted
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
SUPPLY VOLTAGE, VIN
Input voltage range, VIN 3.0 6.0 V
I
Quiescent current
fs = 350 kHz, RT open,
PH pin open 6.2 9.6
mA
I(Q) Quiescent current fs = 500 kHz, RT = 100 kΩ, PH pin open 8.4 12.8 mA
Shutdown, ENA = 0 V 1 1.4
UNDERVOLTAGE LOCKOUT
Start threshold voltage, UVLO 2.95 3.0 V
Stop threshold voltage, UVLO 2.70 2.80 V
Hysteresis voltage, UVLO 0.14 0.16 V
Rising and falling edge deglitch, UVLO(1) 2.5 µs
BIAS VOLTAGE
Output voltage, VBIAS I(VBIAS) = 0 2.70 2.80 2.90 V
Output current, VBIAS (2) 100 µA
CUMULATIVE REFERENCE
Vref Accuracy 0.882 0.891 0.900 V
REGULATION
Line regulation(1)(3)
IL = 1.5 A,fs = 350 kHz, TJ = 85°C 0.07
%/V
Line regulation
(1)(3)
IL = 1.5 A,fs = 550 kHz, TJ = 85°C 0.07 %/V
Load regulation(1)(3)
IL = 0 A to 3 A, fs = 350 kHz, TJ = 85°C 0.03
%/A
Load regulation
(1)(3)
IL = 0 A to 3 A, fs = 550 kHz, TJ = 85°C 0.03 %/A
OSCILLATOR
Internally set—free running frequency RT open 280 350 420 kHz
RT = 180 kΩ (1% resistor to AGND)(1) 252 280 308
Externally set—free running frequency range RT = 100 kΩ (1% resistor to AGND) 460 500 540 kHz
Externally
set free
running
frequency
range
RT = 68 kΩ (1% resistor to AGND)(1) 663 700 762
kHz
Ramp valley(1) 0.75 V
Ramp amplitude (peak-to-peak)(1) 1 V
Minimum controllable on time(1) 200 ns
Maximum duty cycle 90%
(1) Specified by design
(2) Static resistive loads only
(3) Specified by the circuit used in Figure 9
TPS54380-Q1
SLVS836 − JUNE 2008
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4
ELECTRICAL CHARACTERISTICS (continued)
over operating free-air temperature range unless otherwise noted
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
ERROR AMPLIFIER
Error amplifier open-loop voltage gain 1 kΩ COMP to AGND(1) 90 110 dB
Error amplifier unity gain bandwidth Parallel 10 kΩ, 160 pF COMP to AGND(1) 3 5 MHz
Error amplifier common mode input voltage
range Powered by internal LDO(1) 0 VBIAS V
Input bias current, VSENSE VSENSE = Vref 60 250 nA
Output voltage slew rate (symmetric),
COMP(1) 1.0 1.4 V/µs
PWM COMPARATOR
PWM comparator propagation delay time,
PWM comparator input to PH pin (excluding
dead-time)
10-mV overdrive(1) 70 85 ns
ENABLE
Enable threshold voltage, ENA 0.82 1.20 1.40 V
Enable hysteresis voltage, ENA 0.03 V
Falling edge deglitch, ENA(1) 2.5 µs
Leakage current, ENA VI = 5.5 V 1.5 µA
POWER GOOD
Power-good threshold voltage VSENSE falling 90 %Vref
Power-good hysteresis voltage(1) 3 %Vref
Power-good falling edge deglitch(1) 35 µs
Output saturation voltage, PWRGD I(sink) = 2.5 mA 0.18 0.3 V
Leakage current, PWRGD VI = 5.5 V 1µA
CURRENT LIMIT
C t li it t i i t
VI = 3 V Output shorted(1) 4 6.5
A
Current limit trip point VI = 6 V Output shorted(1) 4.5 7.5 A
Current limit leading edge blanking time(1) 100 ns
Current limit total response time(1) 200 ns
THERMAL SHUTDOWN
Thermal shutdown trip point(1) 135 150 165 °C
Thermal shutdown hysteresis(1) 10 °C
OUTPUT POWER MOSFETS
r
Power MOSFET switches
VI = 6 V(4) 59 88
mΩ
rDS(on) Power MOSFET switches VI = 3 V(4) 85 136 mΩ
TRACKIN
Input offset, TRACKIN VSENSE = TRACKIN = 1.25 V(1) −1.5 1.5 mV
Input voltage range, TRACKIN See Note 1 0 Vref V
(1) Specified by design
(2) Static resistive loads only
(3) Specified by the circuit used in Figure 9
(4) Matched MOSFETs low-side rDS(on) production tested, high-side rDS(on) specified by design
TPS54380-Q1
SLVS836 − JUNE 2008
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5
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
AGND
VSENSE
COMP
PWRGD
BOOT
PH
PH
PH
PH
PH
RT
ENA
TRACKIN
VBIAS
VIN
VIN
VIN
PGND
PGND
PGND
PWP PACKAGE
(TOP VIEW)
THERMAL
PAD
TERMINAL FUNCTIONS
TERMINAL
DESCRIPTION
NAME NO. DESCRIPTION
AGND 1 Analog ground. Return for compensation network/output divider, slow-start capacitor, VBIAS capacitor, RT resistor.
Connect PowerPAD to AGND.
BOOT 5 Bootstrap output. 0.022-µF to 0.1-µF low-ESR capacitor connected from BOOT to PH generates floating drive for the
high-side FET driver.
COMP 3 Error amplifier output. Connect frequency compensation network from COMP to VSENSE
ENA 19 Enable input. Logic high enables oscillator, PWM control and MOSFET driver circuits. Logic low disables operation and
places device in low quiescent current state.
PGND 11−13 Power ground. High current return for the low-side driver and power MOSFET. Connect PGND with large copper areas
to the input and output supply returns, and negative terminals of the input and output capacitors. A single-point connection
to AGND is recommended.
PH 6−10 Phase output. Junction of the internal high-side and low-side power MOSFETs and output inductor.
PWRGD 4 Power-good open-drain output. High when VSENSE ≥ 90% Vref, otherwise PWRGD is low.
RT 20 Frequency setting resistor input. Connect a resistor from RT to AGND to set the switching frequency.
TRACKIN 18 External reference input. High impedance input to internal reference/multiplexer and error amplifier circuits.
VBIAS 17 Internal bias regulator output. Supplies regulated voltage to internal circuitry. Bypass VBIAS pin to AGND pin with a high
quality, low-ESR 0.1-µF to 1.0-µF ceramic capacitor.
VIN 14−16 Input supply for the power MOSFET switches and internal bias regulator. Bypass VIN pins to PGND pins close to device
package with a high quality, low-ESR 10-µF ceramic capacitor.
VSENSE 2 Error amplifier inverting input. Connect to output voltage through compensation network/output divider.
TPS54380-Q1
SLVS836 − JUNE 2008
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6
INTERNAL BLOCK DIAGRAM
Falling
Edge
Deglitch
Enable
Comparator
1.2 V
2.95 V
Hysteresis: 0.03 V 2.5 µs
Falling
and
Rising
Edge
Deglitch
2.5 µs
VIN UVLO
Comparator
Hysteresis: 0.16 V
Multiplexer
Reference
−
+
Error
Amplifier
Thermal
Shutdown
150°C
SHUTDOWN
SS_DIS
PWM
Comparator
OSC
Leading
Edge
Blanking
100 ns
RQ
S
Adaptive Dead-Time
and
Control Logic
SHUTDOWN
60 mΩ
VIN
REG
VBIAS
VIN
BOOT
VIN
PH
CO
PGND
PWRGD
Falling
Edge
Deglitch
35 µs
VSENSE
SHUTDOWN
0.90 Vref
Hysteresis: 0.03 Vref
Power-Good
Comparator
AGND VBIAS
ILIM
Comparator
Core
RTCOMPVSENSE
ENA
TPS54380
60 mΩ
LOUT
TRACKIN
25-ns Adaptive
Dead-Time
Sense FET
VIN
I/O
TPS54380-Q1
SLVS836 − JUNE 2008
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7
TYPICAL CHARACTERISTICS
Fi
g
ure 1
0
20
40
60
80
100
120
−40 0 25 85 125
IO = 3 A
VI = 3.3 V
TJ − Junction Temperature − °C
Drain-Source On-State Resistance −
DRAIN-SOURCE ON-STATE RESISTANCE
vs
JUNCTION TEMPERATURE
Ω
Fi
g
ure 2
0
20
40
60
80
100
−40 0 25 85 125
IO = 3 A
VI = 5 V
TJ − Junction Temperature − °C
Drain-Source On-State Resistance −
DRAIN-SOURCE ON-STATE RESISTANCE
vs
JUNCTION TEMPERATURE
Ω
Fi
g
ure 3
450
−40 0 25
f − Internally Set Oscillator Frequency −kHz
550
INTERNALLY SET OSCILLATOR
FREQUENCY
vs
JUNCTION TEMPERATURE
750
85 125
650
350
250
TJ − Junction Temperature − °C
Figure 4
400
−40 0 25
f − Externally Set Oscillator Frequency − kHz
500
EXTERNALLY SET OSCILLATOR
FREQUENCY
vs
JUNCTION TEMPERATURE
800
85 125
700
300
200
TJ − Junction Temperature − °C
600
RT = 68 k
RT = 100 k
RT = 180 k
Figure 5
0.889
−40 0 25
− Voltage Reference − V
VOLTAGE REFERENCE
vs
JUNCTION TEMPERATURE
0.895
85 125
0.893
0.887
0.885
TJ − Junction Temperature − °C
0.891
Vref
Figure 6
0.8850
0.8870
0.8890
0.8910
0.8930
0.8950
3456
f = 350 kHz
TA = 85°C
VI − Input Voltage − V
− Output Voltage Regulation − V
OUTPUT VOLTAGE REGULATION
vs
INPUT VOLTAGE
V
O
Figure 7
f − Frequency − Hz
60
40
0
0 10 100 1 k 10 k 100 k 1 M
Gain − dB
80
100
ERROR AMPLIFIER
OPEN LOOP RESPONSE
140
10 M
120
20
−20
Phase − Degrees
0
−20
−40
−60
−80
−100
−120
−140
−160
−180
−200
RL= 10 kΩ,
CL = 160 pF,
TA = 25°C
Phase
Gain
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2.25
01234
IL − Load Current − A
Device Power Losses − W
DEVICE POWER LOSSES
vs
LOAD CURRENT
TJ − 125°C
fs = 700 kHz
VI = 3.3 V
VI = 5 V
Figure 8
TPS54380-Q1
SLVS836 − JUNE 2008
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8
APPLICATION INFORMATION
Figure 9 shows the schematic diagram for a typical
TPS54380 application. The TPS54380 (U1) can provide
greater than 3 A of output current at a nominal output
voltage of 1.8 V. For proper thermal performance, the
exposed thermal PowerPAD underneath the integrated
circuit package must be soldered to the printed-circuit
board. To provide power-up tracking, the enable of the I/O
supply should be used. If the I/O enable is not used to
power up, then devices with similar undervoltage lockout
thresholds need to be implemented to ensure power-up
tracking. To ensure power-down tracking, the enable pin
must be used.
C7
10 µF
11
R3
Distribution Switch VOUT_I/O
U1
RT
ENA
TRACKIN
VBIAS
VIN
VIN
VIN
PGND
PGND
PGND
PwrPad
AGND
VSENSE
COMP
PWRGD
BOOT
PH
PH
PH
PH
PH
20
19
18
17
16
15
14
13
12
10
9
8
7
6
5
4
3
2
1
10 kΩ
R1
10 kΩ
R4
10 kΩ
R6
9.76 kΩ
VIN
C6
10 µF
C2
1 µFC5
0.047 µF
L1
1 µH
R9
2.4 Ω
C11
3300 pF
C1
120 pF
C4
100 pF
R5
7.15 kΩ
C8
22 µF
C9
22 µF
C10
22 µF
R7
768 Ω
C3
820 pF
R8
9.76 kΩ
R2
71.5 kΩ
Analog and Power Grounds are Tied at
the PowerPAD Under the Package of IC
VOUT_CORE
TPS2013
C12
0.1 µF
Figure 9. Application Circuit
COMPONENT SELECTION
The values for the components used in this design
example were selected for low output ripple voltage and
small PCB area. Additional design information is available
at www.ti.com.
INPUT FILTER
The input voltage is a nominal 5 Vdc. The input filter C6 is
a 10-µF ceramic capacitor (Taiyo Yuden). C7, also a 10-µF
ceramic capacitor (Taiyo Yuden), provides high-frequency
decoupling of the TPS54380 from the input supply and
must be located as close as possible to the device. Ripple
current is carried in both C6 and C7, and the return path to
PGND must avoid the current circulating in the output
capacitors C8, C9, and C10.
FEEDBACK CIRCUIT
The values for these components have been selected to
provide low output ripple voltage. The resistor divider
network of R3 and R8 sets the output voltage for the circuit
at 1.8 V. R3, along with R7, R5, C1, C3, and C4 form the
loop compensation network for the circuit. For this design,
a Type 3 topology is used.
OPERATING FREQUENCY
In the application circuit, the 350-kHz operation is selected
by leaving RT open. Connecting a 180-kΩ to 68-kΩ
resistor between RT (pin 20) and analog ground can be
used to set the switching frequency from 280 kHz to
700 kHz. To calculate the RT resistor, use the following
equation:
R+500 kHz
Switching Frequency 100 [kW](1)
TPS54380-Q1
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9
OUTPUT FILTER
The output filter is composed of a 1-µH inductor and
3 x 22-µF capacitor. The inductor is a low dc resistance
(0.010 Ω) type, Vishay 1HLP2525CZ01. The capacitors
used are 22-µF, 6.3-V ceramic types with X5R dielectric.
An additional high-frequency bypass capacitor, C12, is
also used. The feedback loop is compensated so that the
unity gain frequency is approximately 50 kHz.
PCB LAYOUT
Figure 10 shows a generalized PCB layout guide for the
TPS54380.
The VIN pins should be connected together on the
printed-circuit board (PCB) and bypassed with a low-ESR
ceramic bypass capacitor. Care should be taken to
minimize the loop area formed by the bypass capacitor
connections, the VIN pins, and the TPS54380 ground
pins. The minimum recommended bypass capacitance is
10 µF ceramic with a X5R or X7R dielectric and the
optimum placement is closest to the VIN pins and the
PGND pins.
The TPS54380 has two internal grounds (analog and
power). Inside the TPS54380, the analog ground ties to all
of the noise-sensitive signals, while the power ground ties
to the noisier power signals. Noise injected between the
two grounds can degrade the performance of the
TPS54380, particularly at higher output currents. Ground
noise on an analog ground plane can also cause problems
with some of the control and bias signals. For these
reasons, separate analog and power ground traces are
recommended. There should be an area of ground on the
top layer directly under the IC, with an exposed area for
connection to the PowerPAD. Use vias to connect this
ground area to any internal ground planes. Use additional
vias at the ground side of the input and output filter
capacitors as well. The AGND and PGND pins should be
tied to the PCB ground by connecting them to the ground
area under the device as shown. The only components
that should tie directly to the power ground plane are the
input capacitors, the output capacitors, the input voltage
decoupling capacitor, and the PGND pins of the
TPS54380. Use a separate wide trace for the analog
ground signal path. This analog ground should be used for
the voltage set-point divider, timing resistor RT, and bias
capacitor grounds. Connect this trace directly to AGND
(pin 1).
The PH pins should be tied together and routed to the
output inductor. Because the PH connection is the
switching node, inductor should be located close to the PH
pins and the area of the PCB conductor minimized to
prevent excessive capacitive coupling.
Connect the boot capacitor between the phase node and
the BOOT pin as shown. Keep the boot capacitor close to
the IC and minimize the conductor trace lengths.
Connect the output filter capacitor(s) as shown, between
the VOUT trace and PGND. It is important to keep the loop
formed by the PH pins, Lout, Cout, and PGND as small as
practical.
Place the compensation components from the VOUT trace
to the VSENSE and COMP pins. Do not place these
components too close to the PH trace. Due to the size of
the IC package and the device pinout, they have to be
routed somewhat close, but maintain as much separation
as possible while still keeping the layout compact.
Connect the bias capacitor from the VBIAS pin to analog
ground using the isolated analog ground trace. If an RT
resistor is used, connect it to this trace as well.
LAYOUT CONSIDERATIONS FOR THERMAL
PERFORMANCE
For operation at full rated load current, the analog ground
plane must provide an adequate heat dissipating area. A
3-inch by 3-inch plane of 1-ounce copper is
recommended, though not mandatory, depending on
ambient temperature and airflow. Most applications have
larger areas of internal ground plane available, and the
PowerPAD must be connected to the largest area
available. Additional areas on the top or bottom layers also
help dissipate heat, and any area available must be used
when 3-A or greater operation is desired. Connection from
the exposed area of the PowerPAD to the analog ground
plane layer must be made using 0.013-inch diameter vias
to avoid solder wicking through the vias. Six vias must be
in the PowerPAD area with four additional vias located
under the device package. The size of the vias under the
package, but not in the exposed thermal pad area, can be
increased to 0.018. Additional vias beyond the twelve
recommended that enhance thermal performance must be
included in areas not under the device package.
TPS54380-Q1
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10
AGND
BOOT
VSENSE
COMP
PWRGD
PH
PH
PH
PH
PH
RT
ENA
TRACKIN
VBIAS
VIN
VIN
VIN
PGND
PGND
PGND
VOUT
PH
Vin
TOPSIDE GROUND AREA
VIA to Ground Plane
ANALOG GROUND TRACE
EXPOSED
COMPENSATION
NETWORK
OUTPUT INDUCTOR
OUTPUT
FILTER
CAPACITOR
BOOT
CAPACITOR
INPUT
BYPASS
CAPACITOR
INPUT
BULK
FILTER
BIAS CAPACITOR
TRACKING VOLTAGE
POWERPAD
AREA
RESISTOR DIVIDER
NETWORK
Figure 10. TPS54380 PCB Layout
PERFORMANCE GRAPHS
Figure 11
50
55
60
65
70
75
80
85
90
95
100
0 0.5 1 1.5 2 2.5 3 3.5
VI = 3.3 V
VI = 5 V
Efficiency − %
EFFICIENCY
vs
OUTPUT CURRENT
IO − Output Current − A
Fi
g
ure 12
1.77
1.78
1.79
1.8
1.81
1.82
1.83
0 0.5 1 1.5 2 2.5 3 3.5
OUTPUT VOLTAGE
vs
OUTPUT CURRENT
IO − Output Current − A
− Output Voltage − V
VO
VI = 3.3 V
VI = 5 V
Fi
g
ure 13
1.77
1.78
1.79
1.8
1.81
1.82
1.83
3456
VI− Input Voltage − V
− Output Voltage − V
VO
IO = 0 A
IO = 1.5 A
IO = 3 A
OUTPUT VOLTAGE
vs
INPUT VOLTAGE
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11
Figure 14
−60
−50
−40
−30
−20
−10
0
10
20
30
40
50
60
100 1 k 10 k 100 k 1 M
−180
−150
−120
−90
−60
−30
0
30
60
90
120
150
180
Gain − dB
f − Frequency − Hz
MEASURED LOOP RESPONSE
Phase − Degrees
Gain
Phase
Figure 15
25
35
45
55
65
75
85
95
105
115
125
01234
− Ambient Temperature −
AMBIENT TEMPERATURE
vs
LOAD CURRENT
IL − Load Current − A
C
°
TA
Safe Operating Area(1)
VI = 3.3 V
VI = 5 V
Fi
g
ure 16
Time − 1 µs/div
OUTPUT RIPPLE VOLTAGE
Output Ripple Voltage − 10 mV/div
Figure 17
100 µs/div
20 mV/div
LOAD TRANSIENT RESPONSE
1 A/div
I = 0.75 A to 2.25 A
Figure 18
2 V/div
Vcore
V I/O
V I/O ~Enable
START-UP TIMING
2 ms/div
1 V/div
Figure 19
2 V/div
Vcore
V I/O
V I/O ~Enable
POWER-DOWN TIMING
2 ms/div
1 V/div
(1) Safe operating area is applicable to the test board conditions in the Dissipation Ratings table.
TPS54380-Q1
SLVS836 − JUNE 2008
www.ti.com
12
DETAILED DESCRIPTION
UNDERVOLTAGE LOCKOUT (UVLO)
The TPS54380 incorporates an undervoltage lockout
circuit to keep the device disabled when the input voltage
(VIN) is insufficient. During power up, internal circuits are
held inactive until VIN exceeds the nominal UVLO
threshold voltage of 2.95 V. Once the UVLO start threshold
is reached, device start-up begins. The device operates
until VIN falls below the nominal UVLO stop threshold of
2.8 V. Hysteresis in the UVLO comparator, and a 2.5-µs
rising and falling edge deglitch circuit reduce the likelihood
of shutting the device down due to noise on VIN.
TRACKIN/INTERNAL SLOW-START
The internal slow-start circuit provides start-up slope
control of the output voltage. The nominal internal
slow-start rate is 25 V/ms. When the voltage on TRACKIN
rises faster than the internal slope or is present when
device operation is enabled, the output rises at the internal
rate. If the reference voltage on TRACKIN rises more
slowly, then the output rises at about the same rate as
TRACKIN.
Once the voltage on the TRACKIN pin is greater than the
internal reference of 0.891 V, the multiplexer switches the
noninverting node to the high-precision reference.
ENABLE (ENA)
The enable pin, ENA, provides a digital control enable or
disable (shutdown) for the TPS54380. An input voltage of
1.4 V or greater ensures that the TPS54380 is enabled. An
input of 0.82 V or less ensures that device operation is
disabled. These are not standard logic thresholds, even
though they are compatible with TTL outputs.
When ENA is low, the oscillator, slow-start, PWM control
and MOSFET drivers are disabled and held in an initial
state ready for device start-up. On an ENA transition from
low to high, device start-up begins with the output starting
from 0 V.
VBIAS REGULATOR (VBIAS)
The VBIAS regulator provides internal analog and digital
blocks with a stable supply voltage over variations in
junction temperature and input voltage. A high quality,
low-ESR, ceramic bypass capacitor is required on the
VBIAS pin. X7R- or X5R-grade dielectrics are
recommended because their values are more stable over
temperature. The bypass capacitor must be placed close
to the VBIAS pin and returned to AGND.
External loading on VBIAS is allowed, with the caution that
internal circuits require a minimum VBIAS of 2.70 V, and
external loads on VBIAS with ac or digital switching noise
may degrade performance. The VBIAS pin may be useful
as a reference voltage for external circuits.
VOLTAGE REFERENCE
The voltage reference system produces a precise Vref
signal by scaling the output of a temperature stable
bandgap circuit. During manufacture, the bandgap and
scaling circuits are trimmed to produce 0.891 V at the
output of the error amplifier, with the amplifier connected
as a voltage follower. The trim procedure adds to the
high-precision regulation of the TPS54380, because it
cancels offset errors in the scale and error amplifier
circuits.
OSCILLATOR AND PWM RAMP
The oscillator frequency is set internally to 350 kHz. If a
different frequency of operation is required for the
application, the oscillator frequency can be externally
adjusted from 280 to 700 kHz by connecting a resistor
between the RT pin and AGND. The switching frequency
is approximated by the following equation, where R is the
resistance from RT to AGND:
Switching Frequency +100 kW
R 500 [kHz]
SWITCHING FREQUENCY RT PIN
350 kHz, internally set Float
Externally set 280 kHz to 700 kHz R = 180 kΩ to 68 kΩ
ERROR AMPLIFIER
The high-performance, wide bandwidth, voltage error
amplifier sets the TPS54380 apart from most dc/dc
converters. The user is given the flexibility to use a wide
range of output L and C filter components to suit the
particular application needs. Type-2 or type-3
compensation can be employed using external
compensation components.
PWM CONTROL
Signals from the error amplifier output, oscillator, and
current limit circuit are processed by the PWM control
logic. Referring to the internal block diagram, the control
logic includes the PWM comparator, OR gate, PWM latch,
and portions of the adaptive dead-time and control logic
block. During steady-state operation below the current
limit threshold, the PWM comparator output and oscillator
pulse train alternately reset and set the PWM latch. Once
the PWM latch is reset, the low-side FET remains on for a
minimum duration set by the oscillator pulse width. During
this period, the PWM ramp discharges rapidly to its valley
voltage. When the ramp begins to charge back up, the
low-side FET turns off and high-side FET turns on. As the
PWM ramp voltage exceeds the error amplifier output
voltage, the PWM comparator resets the latch, thus
turning off the high-side FET and turning on the low-side
FET. The low-side FET remains on until the next oscillator
pulse discharges the PWM ramp.
(2)
TPS54380-Q1
SLVS836 − JUNE 2008
www.ti.com
13
During transient conditions, the error amplifier output
could be below the PWM ramp valley voltage or above the
PWM peak voltage. If the error amplifier is high, the PWM
latch is never reset, and the high-side FET remains on until
the oscillator pulse signals the control logic to turn the
high-side FET off and the low-side FET on. The device
operates at its maximum duty cycle until the output voltage
rises to the regulation set-point, setting VSENSE to
approximately the same voltage as VREF. If the error
amplifier output is low, the PWM latch is continually reset
and the high-side FET does not turn on. The low-side FET
remains on until the VSENSE voltage decreases to a
range that allows the PWM comparator to change states.
The TPS54380 is capable of sinking current continuously
until the output reaches the regulation set-point.
If the current limit comparator trips for longer than 100 ns,
the PWM latch resets before the PWM ramp exceeds the
error amplifier output. The high-side FET turns off and
low-side FET turns on to decrease the energy in the output
inductor and consequently the output current. This
process is repeated each cycle in which the current limit
comparator is tripped.
DEAD-TIME CONTROL AND MOSFET
DRIVERS
Adaptive dead-time control prevents shoot-through
current from flowing in both N-channel power MOSFETs
during the switching transitions by actively controlling the
turnon times of the MOSFET drivers. The high-side driver
does not turn on until the voltage at the gate of the low-side
FET is below 2 V. While the low-side driver does not turn
on until the voltage at the gate of the high-side MOSFET
is below 2 V.
The high-side and low-side drivers are designed with
300-mA source and sink capability to quickly drive the
power MOSFETs gates. The low-side driver is supplied
from VIN, while the high-side drive is supplied from the
BOOT pin. A bootstrap circuit uses an external BOOT
capacitor and an internal 2.5-Ω bootstrap switch
connected between the VIN and BOOT pins. The
integrated bootstrap switch improves drive efficiency and
reduces external component count.
OVERCURRENT PROTECTION
The cycle-by-cycle current limiting is achieved by sensing
the current flowing through the high-side MOSFET and
comparing this signal to a preset overcurrent threshold.
The high-side MOSFET is turned off within 200 ns of
reaching the current limit threshold. A 100-ns leading edge
blanking circuit prevents the current limit from false
tripping. Current limit detection occurs only when current
flows from VIN to PH when sourcing current to the output
filter. Load protection during current sink operation is
provided by thermal shutdown.
THERMAL SHUTDOWN
The device uses the thermal shutdown to turn off the power
MOSFETs and disable the controller if the junction
temperature exceeds 150°C. The device is released from
shutdown automatically when the junction temperature
decreases to 10°C below the thermal shutdown trip-point,
and starts up under control of the slow-start circuit.
Thermal shutdown provides protection when an overload
condition is sustained for several milliseconds. With a
persistent fault condition, the device cycles continuously;
starting up by control of the soft-start circuit, heating up due
to the fault condition, and then shutting down on reaching
the thermal shutdown trip-point. This sequence repeats
until the fault condition is removed.
POWER GOOD (PWRGD)
The power-good circuit monitors for under-voltage
conditions on VSENSE. If the voltage on VSENSE is 10%
below the reference voltage, the open-drain PWRGD
output is pulled low. PWRGD is also pulled low if VIN is
less than the UVLO threshold or ENA is low, or a thermal
shutdown occurs. When VIN ≥ UVLO threshold, ENA ≥
enable threshold, and VSENSE > 90% of Vref, the
open-drain output of the PWRGD pin is high. A hysteresis
voltage equal to 3% of Vref and a 35-µs falling edge
deglitch circuit prevent tripping of the power-good
comparator due to high-frequency noise.
PACKAGING INFORMATION
Orderable Device Status (1) Package
Type Package
Drawing Pins Package
Qty Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
TPS54380QPWPRQ1 ACTIVE HTSSOP PWP 20 2000 Green (RoHS &
no Sb/Br) CU NIPDAU Level-3-260C-168 HR
(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.
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 TPS54380-Q1 :
•Catalog: TPS54380
NOTE: Qualified Version Definitions:
•Catalog - TI's standard catalog product
PACKAGE OPTION ADDENDUM
www.ti.com 22-Sep-2008
Addendum-Page 1
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