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Signal
Injection
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Operation
5
SNVU664 – November 2019
Copyright © 2019, Texas Instruments Incorporated
LMR33640EVM User's Guide
•
VOUT -
Power output of EVM. Connect to desired load.
•
VOS -
Output voltage sense connection. Connect to DMM. This is also used for frequency response
analyzer connection.
•
VIS -
Input voltage sense connection. Connect to DMM.
•
GNDS -
Ground sense point for analog measurements. Connect to DMM.
•
VCC -
Test point to measure internal VCC of device; approximately 5 V. An on-board PGOOD pullup
resistor is connected to VCC.
•
EN -
Connection for external EN logic input. Remove EN jumper and connect controlling logic to EN
test point for external enable control.
•
PGOOD -
Power-good flag output. This test point is connected to VCC through a 20 k
Ω
resistor. The
power good function can be monitored at this test point.
•
A -
Connection for frequency response analyzer (on bottom of board). See
.
Figure 5. FRA Setup
2
Operation
Once the previously described connections are made and the appropriate jumpers are set, the EVM is
ready to use. If external control of the EN input is desired, remove the EN jumper and apply the external
signal to the EN test point and GND. The PGOOD output is pulled up to VCC through a 20-k
Ω
resistor.
This way, the PGOOD signal swings from 0 V to about 5 V to indicate when the output voltage is either
outside or inside of the PGOOD window, respectively. If an external pullup and supply is desired for the
PGOOD function, remove the 20-k
Ω
resistor and pull the PGOOD test point up to the desired voltage
through an appropriate resistance. See the
LMR33640 SIMPLE SWITCHER 3.8-V to 36-V, 4-A Step-
for more details.
