EVM Setup
6
SBVU048 – March 2019
Copyright © 2019, Texas Instruments Incorporated
TPS7A78EVM-011 Evaluation module
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
for the proper connections of test equipment.
5.1
Input/Output Connectors and Jumpers Descriptions
5.1.1
J1: V
AC
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
for the proper
connections of test equipment.
HB configuration is achieved by tying V
AC
neutral to the TPS7A78 device GND pin, whereas in FB
configuration V
AC
neutral is connected to the AC– pin and the device GND pin track V
AC
neutral and
therefore must be floating. See
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 V
LDO_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.
