Texas Instruments TPS7A78 User manual

SBVU048–March 2019

TPS7A78EVM-011 Evaluation module

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

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WARNING

General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines

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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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General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines

SBVU048–March 2019

TPS7A78EVM-011 Evaluation module

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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Introduction

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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.

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GND

SC_IN

GND

LDO_OUT

SC_IN

PFD

GND

PFD

100k

SC1

SC2

MAX 26V 2.5A

MAX 16V 1A

MAX 5.5V 300mA

1715721

TP1

AC P

TP8

LDO OUT

TP9

GND

TP10

GND

TP6

PFD

TP2

SC IN

TP11

EXT Pull-up

10µF

DNP

0.33uF

C17

DNP

1uF

10µF

C19

DNP

100uF

C20

DNP

2.21M

22uF

DNP

MAX 8V 1.5A

10µF

DNP

2.2uF

DNP

SC3

SC4

LDO_INMAX 6V 300mA

TP3

LDO IN

0.47uF

DNP

1uF

C10

DNP

470uF

C12

DNP

1000uF

C13

DNP

10µF

C11

GND

PG_S

ACp

ACn

TP4

AC N

GND

2.2uF

C16

DNP

270 VRMS 2.5A 50/60 Hz

270 VRMS 2.5 A 50/60 Hz

3403.0020.11

0.47uF

C15

0.068uF

C14

DNP

PF_S

8200pF C21

DNP

10uF

DNP

1uF

C18

120uF

GND

PG_S

PF_S

PG_S

PF_S

TP7

TP5

Line

Neutral

PF_S PG_S

GND

32Y 4

VCC 5

1Y 6

SN74LVC2G07DBVR

DNP

SC1+

SC1-

SCIN

PFD

AC+

GND 6

AC-

LDO_OUT 8

LDO_IN 9

PF 10

PG 11

GND 12

SC2+ 13

SC2- 14

GND 15

TPS7A7833PWPR

200k

RV1

V430MA7B

280

LDO_IN

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Electrical Performance Specifications

SBVU048–March 2019

TPS7A78EVM-011 Evaluation module

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

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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EVM Setup

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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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EVM Setup

SBVU048–March 2019

TPS7A78EVM-011 Evaluation module

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.

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Time (ms)

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

EVM Setup

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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

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AC Line

AC Neutral

TPS7A78EVM-011

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

Fuse Cap-Drop

TPS7A78

AC+

AC-

GND

TVS

CH.x

When High-Voltage Differential Scope Probes are used, second

surge resistor R7 is not needed; jumper J5 can be shorted

Line

Neutral

AC Power Supply

Oscilloscope

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EVM Setup

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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

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AC Line

AC Neutral

TPS7A78EVM-011

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

Fuse Cap-Drop

TPS7A78

AC+

AC-

GND

TVS

Earth GND

CH.x

Half-Bridge Configuration, jumper J3 is shorted

Default EVM setting

Line

Neutral

AC Power Supply

Oscilloscope

Equipment Connection and Operation

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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.

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