Texas Instruments TPS7A78EVM-011 User manual

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User's Guide
SBVU048–March 2019
TPS7A78EVM-011 Evaluation module
This user’s guide describes the operational use of the TPS7A78EVM-011 evaluation module (EVM) as a
reference design for engineering demonstration and evaluation of the TPS7A78, non-isolated smart linear
voltage regulator (LDO). Included in this user’s guide are setup and operating instructions, thermal and
layout guidelines, a printed circuit board (PCB) layout, a schematic diagram, and a bill of materials (BOM).
Throughout this document, the terms demonstration kit,evaluation board, and evaluation module are
synonymous with the TPS7A78EVM-011.
The following related documents are available through the Texas Instruments web site at www.ti.com.
Table 1. Related Documentation
Device Literature Number
TPS7A78 SBVS343

WARNING
General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines www.ti.com
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Contents
1 General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines ...................... 2
2 Introduction ................................................................................................................... 4
3 Electrical Performance Specifications..................................................................................... 5
4 Schematic..................................................................................................................... 5
5 EVM Setup.................................................................................................................... 6
6 Equipment Connection and Operation.................................................................................... 9
7 PCB Layout ................................................................................................................. 11
8 Bill of Materials (BOM)..................................................................................................... 13
List of Figures
1 TPS7A78EVM-011 Schematic............................................................................................. 5
2 Startup: 120-VAC Half-Bridge (HB) and 27-mA Load Current .......................................................... 8
3 Startup: 120-VAC Full-Bridge (FB) and 55-mA Load Current........................................................... 8
4 Startup: 230-VAC Half-Bridge (HB) and 27-mA Load Current .......................................................... 8
5 Startup: 230-VAC Full-Bridge (FB) and 55-mA Load Current........................................................... 8
6 PF Signal Glitch.............................................................................................................. 8
7 Proper Test Equipment Connections for the FB EVM Configuration ................................................. 9
8 Proper Test Equipment Connections for the Half-Bridge (HB) EVM Configuration ............................... 10
9 Assembly Layer ............................................................................................................ 11
10 Top Layer Routing ......................................................................................................... 11
11 Bottom Layer Routing...................................................................................................... 12
List of Tables
1 Related Documentation..................................................................................................... 1
2 TPS7A78EVM-011 Electrical Performance Specifications ............................................................ 5
3 Test Point Functions ........................................................................................................ 7
4 TPS7A78EVM-011 BOM ................................................................................................. 13
Trademarks
All trademarks are the property of their respective owners.
1 General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines
Always follow TI’s setup and application instructions, including use of all interface components within their
recommended electrical rated voltage and power limits. Always use electrical safety precautions to help
ensure your personal safety and those working around you. Contact TI's Product Information Center
http://support/ti./com for further information.
Save all warnings and instructions for future reference.
WARNING
Failure to follow warnings and instructions may result in personal injury,
property damage or death due to electrical shock and burn hazards.

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The term TI HV EVM refers to an electronic device typically provided as an open framed, unenclosed
printed circuit board assembly. It is intended strictly for use in development laboratory environments,
solely for qualified professional users having training, expertise and knowledge of electrical safety risks in
development and application of high voltage electrical circuits. Any other use and/or application are strictly
prohibited by Texas Instruments. If you are not suitable qualified, you should immediately stop from further
use of the HV EVM.
1. Work Area Safety
a. Keep work area clean and orderly.
b. Qualified observer(s) must be present anytime circuits are energized.
c. Effective barriers and signage must be present in the area where the TI HV EVM and its interface
electronics are energized, indicating operation of accessible high voltages may be present, for the
purpose of protecting inadvertent access.
d. All interface circuits, power supplies, evaluation modules, instruments, meters, scopes and other
related apparatus used in a development environment exceeding 50Vrms/75VDC must be
electrically located within a protected Emergency Power Off EPO protected power strip.
e. Use stable and nonconductive work surface.
f. Use adequately insulated clamps and wires to attach measurement probes and instruments. No
freehand testing whenever possible.
2. Electrical Safety
As a precautionary measure, it is always a good engineering practice to assume that the entire EVM
may have fully accessible and active high voltages.
a. De-energize the TI HV EVM and all its inputs, outputs and electrical loads before performing any
electrical or other diagnostic measurements. Revalidate that TI HV EVM power has been safely
de-energized.
b. With the EVM confirmed de-energized, proceed with required electrical circuit configurations,
wiring, measurement equipment connection, and other application needs, while still assuming the
EVM circuit and measuring instruments are electrically live.
c. After EVM readiness is complete, energize the EVM as intended.
WARNING
While the EVM is energized, never touch the EVM or its electrical
circuits, as they could be at high voltages capable of causing electrical
shock hazard.
3. Personal Safety
a. Wear personal protective equipment (for example, latex gloves or safety glasses with side shields)
or protect EVM in an adequate lucent plastic box with interlocks to protect from accidental touch.
Limitation for safe use:
EVMs are not to be used as all or part of a production unit.

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2 Introduction
Texas Instruments' TPS7A78EVM-011 helps design engineers evaluate the operation and performance of
the TPS7A78 smart linear voltage regulator for possible use in their own circuit application. This particular
EVM is intended for evaluation purposes and is not intended to be an end product. The EVM configuration
contains a single 3.3-V output regulator optimized for e-metering applications. The TPS7A78EVM-011
regulates VAC supply to 3.3-V DC supply and can source up to 27 mA (max) current.
The EVM also features a power-fail detection signal and a power-good indication signal to warrant a VAC
supply failure and to indicate to a microcontroller (MCU) that the regulated DC voltage is greater than 90%
of the targeted regulation DC voltage.
2.1 Before You Begin
This evaluation module is not encapsulated and has exposed terminals with voltages that are connected
to the main AC supply; the following warnings are noted for the safety of anyone using or working close to
the TPS7A78EVM-011. Observe all safety precautions.
WARNING
Failure to adhere to these steps or to not heed the safety
requirements at each step may lead to shock, injury, and damage
to the hardware. Texas Instruments is not responsible or liable in
any way for shock, injury, or damage caused by negligence or
failure to heed advice. If you are not trained in the proper safety of
handling and testing power electronics please do not test this
evaluation module.
WARNING
Danger: HIGH VOLTAGE! This evaluation board is intended for
professional use only. This board has exposed high voltages. Do
not operate this board without proper high-voltage/high-current
safety practices. Read this user guide carefully before testing with
TPS7A78EVM-011. Use floating measurement equipment such as
high-voltage differential scope probes and see Section 5 and
Section 6 for proper EVM setup and test equipment connection.

GND
SC_IN
GND
LDO_OUT
SC_IN
PFD
GND
PFD
100k
R4
100k
R3
SC1
SC2
MAX 26V 2.5A
MAX 16V 1A
MAX 5.5V 300mA
1
2
J2
1715721
TP1
AC P
TP8
LDO OUT
TP9
GND
TP10
GND
TP6
PFD
TP2
SC IN
TP11
EXT Pull-up
10µF
C7
DNP
0.33uF
C17
DNP
1uF
C1
10µF
C19
DNP
100uF
C20
DNP
2.21M
R1
22uF
C6
DNP
MAX 8V 1.5A
10µF
C5
DNP
2.2uF
C4
DNP
SC3
SC4
LDO_INMAX 6V 300mA
TP3
LDO IN
0.47uF
C9
DNP
1uF
C10
DNP
470uF
C12
DNP
1000uF
C13
DNP
10µF
C11
GND
PG_S
ACp
ACn
TP4
AC N
GND
1
2
J1
2.2uF
C16
DNP
270 VRMS 2.5A 50/60 Hz
270 VRMS 2.5 A 50/60 Hz
F1
3403.0020.11
0.47uF
C15
0.068uF
C14
DNP
1 2
J5
PF_S
8200pF C21 DNP
10uF
C2
DNP
1uF
C3
1uF
C18
120uF
C8
1
2
J4
GND
PG_S
PF_S
PG
PF
1
2
J6
1
2
J7
PG_S
PF_S
PG
PF
TP7
PG
TP5
PF
Line
Neutral
PF_S PG_S
1A
1
GND
2
2A
32Y 4
VCC 5
1Y 6
SN74LVC2G07DBVR
U2
DNP
1 2
J3
SC1+
2
SC1-
1
SCIN
3
PFD
4
AC+
5
GND 6
AC-
7
LDO_OUT 8
LDO_IN 9
PF 10
PG 11
GND 12
SC2+ 13
SC2- 14
GND 15
TPS7A7833PWPR
U1
200k
R2
RV1
V430MA7B
280
R5
280
R6
280
R7
LDO_IN
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3 Electrical Performance Specifications
Table 2 lists the electrical specifications for the TPS7A78EVM-011 evaluation board.
(1) All measurements are done with a half-bridge (HB) default EVM setting (unless otherwise noted).
(2) Output current level is determined by the size of the cap-drop (C15), the size of the bulk capacitor (C8), and the device
configuration. When VAC is 70 V (60 Hz), the EVM can source 16 mA (max); see Section 5 for EVM configuration and Section 6
for proper connection of test equipment.
(3) When VAC is 120 V (60 Hz), the EVM can source 55 mA (max) with a full-bridge configuration.
Table 2. TPS7A78EVM-011 Electrical Performance Specifications(1)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
INPUT CHARACTERISTICS
VAC
AC input (RMS) 70 120
V
70 230
Wall plug (RMS) 120
230
fAC Line frequency 45 60/50 Hz
PSTANDBY Standby power VAC = 120 V (60 Hz), IOUT = 0 mA, R6 and R7 are
shorted; see Section 4.104 mW
OUTPUT CHARACTERISTICS
VLDO_OUT Output voltage VAC = 120 V (60 Hz) 3.201 3.3 3.399 V
VLDO_OUT
ripple Output ripple voltage VAC = 120 V (60 Hz) 10 mVpp
IOUT Output current VAC = 120 V (60 Hz) 16(2) 27 55(3) mA
SYSTEMS CHARACTERISTICS
Standby power VAC = 120 V (60 Hz),
IOUT = 0 mA 104 mW
4 Schematic
Figure 1 shows a schematic for the TPS7A78EVM-011.
Figure 1. TPS7A78EVM-011 Schematic

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5 EVM Setup
This section describes how to properly connect and setup the TPS7A78EVM-011, including the jumpers
and connectors on the EVM board. See Section 6 for the proper connections of test equipment.
5.1 Input/Output Connectors and Jumpers Descriptions
5.1.1 J1: VAC
Input AC power-supply connector. Ensure that the AC input power supply is turned off before making the
connection to the EVM. The AC supply line lead must be connected to the line pin on the J1 connector,
whereas the neutral lead must be connected to the neutral pin on the J1 connector to ensure proper
operation of the TPS7A78 LDO.
NOTE: If the AC supply line and neutral leads are flipped when connected to the J1 connector, then
the TPS7A78 device GND pin is referenced to the AC supply line and only floating
measurement equipment must be used.
5.1.2 J3: Full-Bridge (FB) and Half-Bridge (HB) Configurations
This EVM comes configured for half-bridge (HB) configuration usage, when J3 jumper is connected.
However, to use the full-bridge (FB) configuration, leave jumper J3 open and see Section 6 for the proper
connections of test equipment.
HB configuration is achieved by tying VAC neutral to the TPS7A78 device GND pin, whereas in FB
configuration VAC neutral is connected to the AC– pin and the device GND pin track VAC neutral and
therefore must be floating. See Section 6 for the proper connections of test equipment.
NOTE: When FB configuration is used, the device GND must float (that is, the device GND must not
be tied to Earth-GND). Floating the device GND is required to limit the shunted AC current
(the excess AC current charging the bulk capacitor C8) while the device active bridge shunts
this current to circulate this current back to neutral. Jumper J5 is open by default to limit the
circulating current though neutral when the device GND is intentionally or accidentally
connected to Earth-GND, such as when using regular scope probes or a bench digital
multimeter (DMM) where such equipment have their GNDs always tied to Earth-GND. Use
floating measurement equipment when the FB EVM configuration is used.
5.1.3 J4: Power-Good Indication and Power-Fail Detection Pullup Voltage
Jumper J4 pulls up the open-drain power-good and power-fail detection indicators to VLDO_IN by athe
default EVM setting. An external DC pullup voltage can be used via test point TP11; however, jumper J4
must be open in order not to short the external pullup voltage to the LDO_IN pin.
NOTE: When an external DC voltage is used to pullup the PG and PF pins, this external supply
must be a floating supply when FB configuration is used.
For HB configuration, the device GND can be tied to Earth-GND, and the external pullup
supply can be referenced to the device GND.
5.1.4 J5: Second Surge Resistor (R7) Jumper
This EVM has three surge resistors, R5, R6, and R7. However, only one resistor R5 is required. R7 is
needed when the device GND is tied to Earth-GND intentionally or accidentally when using regular scope
probes.
R6 was populated for test purposes only. Capacitor C21 is a placeholder for conducting electromagnetic
interference (EMI) filtering.

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5.1.5 J6 and J7: Power-Good (PG) and Power-Fail (PF) Signals
The TPS7A78 device has two open-drain signals (power-good and power-fail) that are both pulled up to
VLDO_IN by default.
Becuase of the high-impedance open-drain logic, the AC supply frequency noise may be present on those
signals when they are high. A low-impedance digital buffer isolation circuit is recommended, such as the
U2 device in Section 4, to obtain noise-free PG ans PF signals. Jumpers J6 and J7 connect the device PG
and PF signals directly to the TP7 and TP5 test points because the digital buffer circuit is not populated
with the default EVM setting.
NOTE: When high-voltage differential scope probes are used when testing the TPS7A78EVM-011,
the digital buffer circuit U2 in Section 4 is recommended to be populated and jumpers J6 and
J7 must be open to obtain noise-free PG and PF signals.
5.1.6 J2: VLDO_OUT
Regulated DC output voltage connector.
NOTE: This EVM is optimized for a 3.3-V output and a 27-mA to 55-mA (max) load current. If your
application requires higher output current, see the TPS7A78 Application and Implementation
section for the proper setting of your application requirement.
5.2 Test Points
Table 3 lists the test points for the TPS7A78EVM-011.
Table 3. Test Point Functions
TEST POINTS NAME DESCRIPTION
TP1 AC_P AC supply line input to the device after the cap-drop capacitor and surge
resistor.
TP2 SC_IN Rectified DC voltage pin; see the TPS7A78 Application and Implementation
section for the proper setting of your application requirement.
TP3 LDO_IN Charge-pump output pin.
TP4 AC_N AC supply neutral input to the device after the cap-drop capacitor and surge
resistor.
TP5 PF Power-fail pin.
TP6 PFD Power-fail detect pin.
TP7 PG Power-good pin.
TP8 LDO_OUT Regulated DC output pin.
TP9 GND Device GND connected to the thermal pad.
TP10 GND
5.3 Performance Data for the TPS7A78EVM-011
As specified in Section 5.1.2, this EVM is configured for an HB 3.3-V output voltage and 27 mA of output
current, and the EVM can also be configured for FB use.

Time (ms)
Voltage (V) Voltage (V)
0 1 2 3 4 5 6 7 8 9 10
0 0
1 8
2 16
3 24
4 32
5 40
6 48
VLDO_OUT
VPF VAC_P
Time (sec)
DC Voltage (V)
AC Voltage (V)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-1 -400
0 0
1 400
2 800
3 1200
4 1600
5 2000
VLDO_IN
VLDO_OUT VAC VPG
Time (sec)
DC Voltage (V)
AC Voltage (V)
0 0.1 0.2 0.3 0.4 0.5
-1 -400
0 0
1 400
2 800
3 1200
4 1600
5 2000
VLDO_IN
VLDO_OUT VAC VPG
Time (sec)
DC Voltage (V)
AC Voltage (V)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-1 -200
0 0
1 200
2 400
3 600
4 800
5 1000
VLDO_IN
VLDO_OUT VAC VPG
Time (sec)
DC Voltage (V)
AC Voltage (V)
0 0.1 0.2 0.3 0.4 0.5
-1 -200
0 0
1 200
2 400
3 600
4 800
5 1000
VLDO_IN
VLDO_OUT VAC VPG
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5.3.1 Startup
Figure 2 to Figure 5 show various start-up plots for the TPS7A78EVM-011.
Figure 2. Startup: 120-VAC Half-Bridge (HB) and 27-mA
Load Current Figure 3. Startup: 120-VAC Full-Bridge (FB) and 55-mA Load Current
Figure 4. Startup: 230-VAC Half-Bridge (HB) and 27-mA
Load Current Figure 5. Startup: 230-VAC Full-Bridge (FB) and 55-mA Load Current
In Figure 6, the power-fail detect (PFD) trace and resistor divider was placed close to the AC_P pin and as
a result the power-fail (PF) signal glitches whenever there is a shunt event; see the TPS7A78 Feature
Description section for details on the device active bridge control. Figure 6 shows the PF signal glitch.
Figure 6. PF Signal Glitch

AC Line
AC Neutral
TPS7A78EVM-011
J1
High-Voltage
Differential
Scope Probe
Device GND must be floating and must not be tied to Earth-GND
when Full-Bridge configuration is used.
Use differential measurement as shown below
Device GND
LDO_OUT
Earth GND TP8TP10TP9
Earth GND
Load
J2
J3
R5
Fuse Cap-Drop
TPS7A78
AC+
AC-
GND
TVS
CH.x
R7
J5
xx
When High-Voltage Differential Scope Probes are used, second
surge resistor R7 is not needed; jumper J5 can be shorted
xx
Line
Neutral
AC Power Supply
Oscilloscope
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5.4 Soldering Guidelines
To avoid damaging the LDO, use a hot-air system for any solder rework to modify the EVM for the
purpose of repair or other application reasons.
6 Equipment Connection and Operation
6.1 Equipment Connection
Connect test equipment as described in this section and follow the listed steps to properly take
measurements:
NOTE: The FB configuration for the EVM requires a differential measurement. The TPS7A78 device
GND must not be tied to Earth-GND.
6.1.1 Full-Bridge (FB) Test Equipment Connection
Figure 7 shows an FB connection diagram.
Figure 7. Proper Test Equipment Connections for the FB EVM Configuration

AC Line
AC Neutral
TPS7A78EVM-011
J1
Regular Scope
Probe or
High-Voltage
Differential
Scope Probes
Device GND can be floating or tied to Earth GND when Half-Bridge
configuration is used.
Device GND
LDO_OUT
Earth GND TP8TP10TP9
Load
J2
J3
R5
Fuse Cap-Drop
TPS7A78
AC+
AC-
GND
TVS
x
x
Earth GND
CH.x
R7
J5
Half-Bridge Configuration, jumper J3 is shorted
Default EVM setting
xx
Line
Neutral
AC Power Supply
Oscilloscope
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6.1.2 Half-Bridge (HB) Test Equipment Connection
Figure 8 shows an HB connection diagram.
Figure 8. Proper Test Equipment Connections for the Half-Bridge (HB) EVM Configuration
To ensure proper connectivity:
1. Set the AC input power supply to 120 VAC and 60 Hz, and turn the power supply off.
2. Connect the line lead from the AC power supply to the line pin on the J1 connector of the EVM.
3. Connect the neutral lead from the AC power supply to the neutral pin on the J1 connector of the EVM.
4. Connect a 0-mA to 27-mA load between J2 connecter terminals of the EVM.
6.2 Equipment Operation
Operate the test equipment using the following steps:
1. Turn on the AC power supply.
2. Vary the respective load and input voltage, as necessary, for test purposes.