Texas Instruments TPS54A20EVM-770 User manual

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TPS54A20EVM-770, 10-A, SWIFT™ regulator evaluation module
User's Guide
SLVUAM8A–December 2015–Revised March 2019
TPS54A20EVM-770, 10-A, SWIFT™ regulator evaluation
module
This user’s guide contains information for the TPS54A20EVM-770 evaluation module (PWR770) as well
as for the TPS54A20 dc/dc converter. Also included are the performance specifications, the schematic,
and the bill of materials for the TPS54A20EVM-770.
Contents
1 Introduction ................................................................................................................... 2
2 Test Setup and Results..................................................................................................... 4
3 Board Layout................................................................................................................ 14
4 Schematic and Bill of Materials........................................................................................... 16
List of Figures
1 TPS54A20EVM-770 Efficiency............................................................................................. 6
2 TPS54A20EVM-770 Low Current Efficiency............................................................................. 6
3 TPS54A20EVM-770 Load Regulation .................................................................................... 7
4 TPS54A20EVM-770 Line Regulation ..................................................................................... 7
5 TPS54A20EVM-770 Transient Response................................................................................ 8
6 TPS54A20EVM-770 Loop Response ..................................................................................... 8
7 TPS54A20EVM-770 Output Ripple, 0 A Load........................................................................... 9
8 TPS54A20EVM-770 Output Ripple, 5 A Load........................................................................... 9
9 TPS54A20EVM-770 Output Ripple, 10 A Load........................................................................ 10
10 TPS54A20EVM-770 Input Ripple, 0 A Load............................................................................ 10
11 TPS54A20EVM-770 Input Ripple, 5 A Load............................................................................ 11
12 TPS54A20EVM-770 Input Ripple, 10 A Load .......................................................................... 11
13 TPS54A20EVM-770 Start-Up Relative to VIN........................................................................... 12
14 TPS54A20EVM-770 Start-Up Relative to Enable...................................................................... 12
15 Thermal Image ............................................................................................................. 13
16 TPS54A20EVM-770 Top-Side Assembly ............................................................................... 14
17 TPS54A20EVM-770 Top-Side Layout................................................................................... 14
18 TPS54A20EVM-770 Internal Layer-1 Layout........................................................................... 14
19 TPS54A20EVM-770 Internal Layer-2 Layout........................................................................... 14
20 TPS54A20EVM-770 Bottom-Side Layout............................................................................... 14
21 TPS54A20EVM-770 Schematic.......................................................................................... 16
List of Tables
1 Input Voltage and Output Current Summary............................................................................. 3
2 TPS54A20EVM-770 Performance Specification Summary ............................................................ 3
3 EVM Connectors and Test Points......................................................................................... 5
4 TPS54A20EVM-770 Bill of Materials .................................................................................... 17
Trademarks
SWIFT is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.

!
Introduction www.ti.com
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1 Introduction
1.1 Before You Begin
The following warnings and cautions are noted for the safety of anyone using or working close to the
TPS54A20EVM-770. Observe all safety precautions.
Warning The TPS54A20EVM-770 circuit module may become hot
during operation due to dissipation of heat. Avoid contact with
the board. Follow all applicable safety procedures applicable
to your laboratory.
Caution Do not leave the EVM powered when unattended.
WARNING
The circuit module has signal traces, components, and component
leads on the bottom of the board. This may result in exposed
voltages, hot surfaces or sharp edges. Do not reach under the
board during operation.
CAUTION
The circuit module may be damaged by over temperature. To avoid damage,
monitor the temperature during evaluation and provide cooling, as needed, for
your system environment.
CAUTION
Some power supplies can be damaged by application of external voltages. If
using more than 1 power supply, check your equipment requirements and use
blocking diodes or other isolation techniques, as needed, to prevent damage to
your equipment.

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1.2 Background
The TPS54A20 dc/dc converter is a two-phase synchronous series capacitor buck converter designed to
provide up to a 10-A output. The input (VIN) is rated for 8 V to 14 V. Rated input voltage and output
current range for the evaluation module are given in Table 1. This evaluation module is designed to
demonstrate the small printed-circuit-board areas that may be achieved when designing with the
TPS54A20 regulator. The switching frequency is externally set at a nominal 2 MHz for each side, 4 MHz
effective. The high-side and low-side MOSFETs are incorporated inside the TPS54A20 package along
with the gate drive circuitry. The low drain-to-source on-resistance of the MOSFET allows the TPS54A20
to achieve high efficiencies and helps keep the junction temperature low at high output currents. The
compensation components are internal to the integrated circuit (IC), and an external divider allows for an
adjustable output voltage. Additionally, the TPS54A20 provides adjustable slow start and undervoltage
lockout inputs. The absolute maximum input voltage is 15 V while switching and 17 V for non-switching
conditions.
Table 1. Input Voltage and Output Current Summary
EVM INPUT VOLTAGE RANGE OUTPUT CURRENT
RANGE
TPS54A20EVM-770 VIN = 9.2 V to 14 V 0 A to 10 A
1.3 Performance Specification Summary
A summary of the TPS54A20EVM-770 performance specifications is provided in Table 2. Specifications
are given for an input voltage of VIN = 12 V and an output voltage of 1.2 V, unless otherwise specified. The
TPS54A20EVM-770 is designed and tested for VIN = 9.2 V to 14 V. The ambient temperature is 25°C for
all measurements, unless otherwise noted.
Table 2. TPS54A20EVM-770 Performance Specification Summary
SPECIFICATION TEST CONDITIONS MIN TYP MAX UNIT
VIN voltage range 9.2 12 14 V
VIN start voltage 9.39 V
VIN stop voltage 9.14 V
Output voltage setpoint 1.2 V
Output current range VIN = 9.2 V to 14 V 0 10 A
Line regulation IO= 5 A, VIN = 9.2 V to 14 V ±0.04%
Load regulation VIN = 12 V, IO= 0 A to 10 A ±0.03%
Load transient response IO= 0 A to 9 A Voltage change –60 mV
Recovery time 60 µs
IO= 9 A to 0 A Voltage change 60 mV
Recovery time 60 µs
Loop bandwidth VIN = 12 V, IO= 5 A 280 kHz
Phase margin VIN = 12 V , IO= 5 A 45 degree
Input ripple voltage IO= 10 A 90 mVPP
Output ripple voltage IO= 10 A 20 mVPP
Output rise time 512 µs
Operating frequency 2 MHz
Maximum efficiency TPS54A20EVM-770, VIN = 9 V, IO= 5 A 84.7%

EN(TOP) EN
EN(BOT)
IN(FALL) EN EN(TOP) EN(FALL)
R V
R = V - V
x
+ xR I
IN(RISE) IN(FALL)
EN(TOP)
EN(FALL) EN(RISE)
V - V
R = I - I
(TON) OUT
R 3 k 15 k x V= +
( )
(BOT) OUT REF
(TOP)
REF
R x V - V
RV =
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1.4 Modifications
These evaluation modules are designed to provide access to the features of the TPS54A20. Some
modifications can be made to this module.
1.4.1 Output Voltage Setpoint
The output voltage is set by the resistor divider network of R9 (R(TOP)) and R7 (R(BOT)). R7 is fixed at 14.3
kΩ. To change the output voltage of the EVM, it is necessary to change the value of resistor R9. Changing
the value of R9 can change the output voltage above the 0.508 V reference voltage VREF. The value of R9
for a specific output voltage can be calculated using Equation 1.
(1)
1.4.2 On Time
The TON pin requires a resistor to set the nominal on-time and to support the input voltage feed forward
circuit. The resistance value used also influences the internal ramp in the controller. UseEquation 2 for
selecting the TON resistor.
(2)
The RTON resistor selected for this design example is 22.1 kΩ. During startup, the converter uses the
nominal on-time programmed through TON. The phase lock loop (PLL) is only activated after startup is
complete. When the PLL is engaged, the on-time is adjusted. If the nominal on-time programmed
through the TON pin is not close to the on-time when the PLL is engaged, the SYNC range of the
device may be reduced. The TON resistor can also be adjusted to tune the controller. Lowering the
RTON value will increase the internal ramp height. This will reduce the converter’s sensitivity to noise
and jitter but it will also reduce the transient response capabilities of the converter.
1.4.3 Adjustable UVLO
The undervoltage lockout (UVLO) can be adjusted externally using R2 (REN(TOP)) and R3 (REN(BOT)). The
EVM is set for a start voltage of 9.385 V and a stop voltage of 9.144 V using R2 = 80.6 kΩand R3 = 12.4
kΩ. Use Equation 3 and Equation 4 to calculate required resistor values for different start and stop
voltages. IEN(FALL) = 4 µA, IEN(RISE) = 1 µA and VEN = 1.23 V
(3)
(4)
2 Test Setup and Results
This section describes how to properly connect, set up, and use the TPS54A20EVM-770 evaluation
module. The section also includes test results typical for the evaluation module and covers efficiency,
output voltage regulation, load transients, loop response, output ripple, input ripple, and start-up.
2.1 Input/Output Connections
The TPS54A20EVM-770 is provided with input/output connectors and test points as shown in Table 3. A
power supply capable of supplying greater than 2 A must be connected to J1 through a pair of 20 AWG
wires or better. The load must be connected to J4 through a pair of 20 AWG wires or better. The
maximum load current capability is 10 A. Wire lengths must be minimized to reduce losses in the wires.
Test-point TP1 provides a place to monitor the VIN input voltages with TP2 providing a convenient ground
reference. TP7 is used to monitor the output voltage with TP8 as the ground reference.

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Table 3. EVM Connectors and Test Points
Reference Designator Function
J1 VIN input voltage connector. (See Table 1 for VIN range).
J2 2-pin header for enable. Connect EN to ground to disable, open to enable.
J3 External VG+ header. To improve converter efficiency, an external 5V supply is recommended to be
connected to the VG+ pin (J3-2) to GND (J3-1).
J4 VOUT, 1.2 V at 10 A maximum.
TP1 VIN test point.
TP2 GND test point at VIN connector.
TP3 PGOOD test point.
TP4 SYNC test point.
TP5 VG+ test point.
TP6 Test point between voltage divider network and output. Used for loop response measurements.
TP7 Output voltage test point.
TP8 GND test point
TP9 Test point at gate of transient load circuit.
TP10 GND test point at input of transient load circuit.
TP11 Test point at top of transient load circuit load resistor
TP12 Test point at bottom (GND) of transient load circuit load resistor
TP13 Analog ground (AGND) test point.

Output Current (A)
Efficiency (%)
0.001 0.01 0.1 1 10
0
10
20
30
40
50
60
70
80
90
100
D002
VIN = 9V
VIN = 12V
VIN = 14V
Output Current (A)
Efficiency (%)
0 1 2 3 4 5 6 7 8 9 10
0
10
20
30
40
50
60
70
80
90
100
D001
VIN = 9V
VIN = 12V
VIN = 14V
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2.2 Efficiency
The efficiency of this EVM peaks at a load current of about 5 A and then decreases as the load current
increases toward full load. Figure 1 shows the efficiency for the TPS54A20EVM-770 at an ambient
temperature of 25°C.
Figure 1. TPS54A20EVM-770 Efficiency
Figure 2 shows the efficiency for the TPS54A20EVM-770 using a semi-log scale to more easily show
efficiency at lower output currents. The ambient temperature is 25°C.
Figure 2. TPS54A20EVM-770 Low Current Efficiency
The efficiency may be lower at higher ambient temperatures, due to temperature variation in the drain-to-
source resistance of the internal MOSFET.

Input Voltage (V)
Line Regulation (%)
9 10 11 12 13 14
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
D004
Output Current (A)
Load Regulation (%)
0 1 2 3 4 5 6 7 8 9 10
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
D003
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2.3 Output Voltage Load Regulation
Figure 3 shows the load regulation for the TPS54A20EVM-770.
Figure 3. TPS54A20EVM-770 Load Regulation
Measurements are given for an ambient temperature of 25°C.
2.4 Output Voltage Line Regulation
Figure 4 shows the line regulation for the TPS54A20EVM-770.
Figure 4. TPS54A20EVM-770 Line Regulation

Frequency (Hz)
Gain (dB)
Phase (Degrees)
100 200300 500 1000 2000 5000 10000 20000 50000100000 1000000
-60 -180
-50 -150
-40 -120
-30 -90
-20 -60
-10 -30
0 0
10 30
20 60
30 90
40 120
50 150
60 180
EVMU
V = 50 mV / div (ac coupled)
O
Time = 50 µsec / div
I = 5 A / div
O
Load step = 0 A - 9 A, slew rate = 9 A / µsec
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2.5 Load Transients
Figure 5 shows the TPS54A20EVM-770 response to load transients. The current step is from 0 A to 9 A.
The current step slew rate is 9 A/µs. Total peak-to-peak voltage variation is as shown, including ripple and
noise on the output. The transient waveform is measured using the on-board fast transient circuit.
CAUTION
Q1 may get hot. Limit the power dissipation to 3W or less. Use low duty cycles.
Figure 5. TPS54A20EVM-770 Transient Response
2.6 Loop Characteristics
Figure 6 shows the TPS54A20EVM-770 loop-response characteristics. Gain and phase plots are shown
for VIN voltage of 12 V. Load current for the measurement is 5 A.
Figure 6. TPS54A20EVM-770 Loop Response

V = 20 mV / div (ac coupled)
O
Time = 200 nsec / div
SWA = 5 V / div
SWB = 5 V / div
V = 20 mV / div (ac coupled)
O
Time = 200 nsec / div
SWA = 5 V / div
SWB = 5 V / div
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2.7 Output Voltage Ripple
Figure 7,Figure 8, and Figure 9 show the TPS54A20EVM-770 output voltage ripple. The load currents are
0A,5Aand10A.VIN = 12 V. The ripple voltage is measured directly across TP7 and TP8.
Figure 7. TPS54A20EVM-770 Output Ripple, 0 A Load
Figure 8. TPS54A20EVM-770 Output Ripple, 5 A Load

V = 50 mV / div (ac coupled)
I
Time = 200 nsec / div
SWA = 5 V / div
SWB = 5 V / div
V = 20 mV / div (ac coupled)
O
Time = 200 nsec / div
SWA = 5 V / div
SWB = 5 V / div
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Figure 9. TPS54A20EVM-770 Output Ripple, 10 A Load
2.8 Input Voltage Ripple
Figure 10,Figure 11 and Figure 12 show the TPS54A20EVM-770 input voltage ripple. The load currents
are 0 A, 5 A and 10 A. VIN = 12 V. The ripple voltage is measured directly across TP1 and TP2.
Figure 10. TPS54A20EVM-770 Input Ripple, 0 A Load