SNVU838A October   2022  – November 2022 LMR51450

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 LMR51450 Synchronous Step-Down Voltage Converter
    2. 1.2 LMR51450 Evaluation Module
  4. 2Quick Start
  5. 3Detailed Descriptions
    1. 3.1 Connectors
    2. 3.2 Jumpers
  6. 4Schematic
  7. 5Board Layout
  8. 6Bill of Materials
  9. 7Revision History

3.1 Connectors

This section describes the connectors on the EVM and how to properly connect, set up, and use the EVM. See Figure 2-1 for a top view of the EVM.

    VOUTOutput voltage of the converter

    The VOUT connector connects to the power inductor and output capacitors. Connect the load between VOUT connector and the GND connector right next to it to provide load current. Connect the loading device to the board with short and thick wires to handle the large DC output current.

    GND1-GND5Ground of the converter

    The GND is connected to the PGND and AGND pins of the device, as well as the ground of the input and output capacitors. The GND connections next to VIN, VIN_EMI, and VOUT connectors are meant for current return path for the supply voltage and load, respectively. Connectors are provided in pairs to allow easy and accurate sensing of voltages. Connect to supply and load grounds with short and thick wires. Other GND connectors are for signal measurement and probing.

    VINInput voltage to the converter

    The VIN connector connects to the input capacitors and the VIN pins of the LMR51450. Connect the supply voltage from a power supply or a battery between VIN and GND connectors as power input to the device. The voltage range must be higher than 3.9 V for the device to start up. VIN higher than 6 V provides regulated 5-V output voltage. VIN must be no higher than 36 V to avoid damaging the device. After start-up, the device stays active until VIN drops below 3.4 V. The current limit on the supply must be high enough to provide the needed supply current. Otherwise, the supply voltage does not maintain the desired voltage. The supply voltage must be connected to the board with short and thick wires to handle the pulsing input current.

    VIN_EMIInput voltage to input filter of the converter

    LMR51450 EVM provides the option for the use of input filter. C1, C2 and L4 are placeholders for input filter networks to be populated. If the input filter is desired between the supply and the LMR51450, put C1, C2, and L4 on the board and connect the supply voltage between VIN_EMI and GND_EMI connectors. The supply voltage must be connected to the board with short and thick wires to handle pulsing input current. The output of the filter is connected to VIN, which is connected to the VIN pins of the LMR51450 and the input capacitors.

    GND_EMIGround return for the input filter

    This connector is the current return path for the supply connected to VIN_EMI. This connector provides a short-loop connection to the input filter capacitors to best filter the conducted noise generated from the PCB. Use VIN_EMI and GND_EMI connection if input filter is used and conducted EMI test is desired.

    ENTo monitor the EN pin or input EN control signal

    This test point is used to monitor the voltage on the device EN pin. By default, the EN pin is connected to Vin.

    PGTo monitor the PGOOD pin

    The PGOOD flag indicates whether the output voltage is within the regulation band. The PGOOD pin of the device is an open-drain output and it is pulled up to VOUT on this board through a pullup resistor. This flag is high impedance when the output voltage is in regulation.

    VO

    This connector is provided to allow VOUT to be measured more accurately.

    VI

    This connector is provided to allow VIN to be measured more accurately.