This section describes the connectors and the test
points on the EVM and how to properly connect, set up, and use the LMR38020QEVM. See Figure 2-1 for a top view
of the EVM.
VOUT (J2)Output voltage of the converterVOUT 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.
GNDGround of the converterIt is connected to the LMR38020-Q1 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 converterVIN connector and test point connects to the input capacitors and the VIN pin of the LMR38020-Q1. Connect the supply
voltage from a power supply or a battery between the VIN and GND connectors.
The voltage range should be higher than 4.2 V for the device to be active.
VVIN higher than 6 V provides a regulated 5-V output voltage.
To avoid damaging the device, VVIN 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.
VIN_EMIInput voltage to input filter of the converterIf an input filter is desired between the supply voltage and the LMR38020-Q1, connect the supply
voltage between VIN_EMI and GND on the 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 GNDGround connection near the input EMI filterThis is the current return path for the supply connected to VIN_EMI. It provides a direct connection to the input filter capacitors to filter conducted noise generated by the converter. Use VIN_EMI and GND connections at the input filter to minimize EMI.
SYNC (J5)SYNC clock injectionJ5 is used to synchronize the switching frequency to external clock. Refer to the LMR38020-Q1 SIMPLE SWITCHER? 4.2-V to
80-V, 2-A Synchronous Buck Converter Data Sheet for
detail application information.Do not short J5
SYNC pin to ground.
EN (J4)Set EN pin optionsUse this jumper to enable/disable the LMR38020-Q1. PIN-1 is connected to
GND and PIN-2 is connected to EN.
- Connect PIN-1 to
PIN-2 to disable the device.
- 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, R7, was not assembled on this
board, so the EN/UVLO voltage pulls up to the input voltage.Calculate the lower UVLO
resistor, R7, based on the desired turn-on voltage and the
upper UVLO resistor, R5, of 115 KΩ. Refer to the External
UVLO section of the LMR38020-Q1 SIMPLE SWITCHER? 4.2-V to 80-V, 2-A Synchronous
Buck Converter Data Sheet for more detailed
application information.
PWRGD (J1)Power-good indicationPWRGD jumper with PIN-1 connected to PGOOD and
PIN-2 connected to the pullup 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-Q1 PGOOD is an
open-drain output that is tied to voltage below 20 V through pullup
resistor R10.
Header (J6)Measure VOUT and loop responseJ6 PIN-2 (VO_S) is connected to the output for output voltage sensing and efficiency
measurement. PIN-1 (VINJ) is connected to the noise injection
resistor R3. The loop response can be measured on J6.