2.2 Detailed Descriptions
This section describes the connectors and the test points on the EVM and how to properly connect, set up and
use the LMR38020EVM. See
VOUT (J2)
Output voltage of the converter
VOUT connector and test point connected to the power inductor and the output capacitors.
Connect the loading device between VOUT and GND connectors to provide loading to the
regulator. Connect the loading device to the board with short wires to handle the DC output current.
GND
Ground of the converter
It is connected to the LMR38020 GND as well as the return terminals of the input and output
capacitors. GND is the current return path for both supply voltage and load. Connect to supply and
load grounds with short wires.
VIN (J3)
Input voltage to the converter
VIN connector and test point connects to the input capacitors and the VIN pin of the LMR38020.
Connect the supply voltage from a power supply or a battery between the VIN and GND
connectors. The voltage range should be higher than 4.5 V for the device to be active. V
VIN
higher
than 6 V provides a regulated 5 V output voltage. To avoid damaging the device V
VIN
should be
no greater than 80 V. The current limit on the supply should be high enough to provide the needed
supply current when the output is fully loaded. The supply voltage should be connected to the
board with short wires.
EMI IN+
Input voltage to input filter of the converter
If an input filter is desired between the supply voltage and the LMR38020, connect the supply
voltage between EMI IN+ and EMI GND on bottom layer. The supply voltage should be connected
to the board with short wires.
The EMI filter components were not assembled on this evaluation board.
EMI GND
Ground connection near the input filter
This is the current return path for the supply connected to EMI IN+. It provides a direct connection
to the input filter capacitors to filter conducted noise generated by the converter. Use EMI IN+ and
EMI GND connections at the input filter to minimize EMI.
SYNC (J5)
SYNC clock injection
J5 is used to synchronize the switching frequency to external clock. Refer to data sheet for detail
application information.
Do NOT short J5 SYNC pin to ground.
EN (J4)
Set EN pin options
Use this jumper to enable/disable the LMR38020. PIN-1 is connected to GND and PIN-2 is
connected to EN.
1. Connect PIN-1 to PIN-2 to disable the device.
2. Leave PIN-1 and PIN-2 open for EN to be connected to VIN through a resistor divider.
The system UVLO voltage can be programmed by resistor divider on EN pin. The lower UVLO
resistor, R
7,
was not assembled on this board, so the EN/UVLO voltage pulls up to the input
voltage.
Calculate the lower UVLO resistor, R
7
, based on the desired turn-on voltage and the upper UVLO
resistor, R
5
, of 115 KΩ. Refer to LMR38020 data sheet "External UVLO" section for more detail
application information.
PWRGD
(J1)
Power Good indication
PWRGD jumper with PIN-1 connected to PGOOD and PIN-2 connected to Pull-Up voltage. PIN-1
can be used as a test point to monitor the power-good indicator. This flag indicates whether the
output voltage has reached its regulation level. The LMR38020 PGOOD is an open-drain output
that is tied to voltage below 20 V through pull-up resistor R
10
.
LMR38020 Evaluation Module
SNVU787 – JULY 2021
LMR38020EVM User Guide
5
Copyright © 2021 Texas Instruments Incorporated
