SNVU682A July   2019  – March 2021 LM61495-Q1

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 LM61495RPHEVM Synchronous Step-Down Voltage Converter
  3. 2Quick Start
  4. 3Detailed Descriptions
  5. 4Schematic
  6. 5Board Layout
  7. 6Board Curves
  8. 7Bill of Materials
  9.   Revision History

3 Detailed Descriptions

This section describes the connectors and the test points on the EVM.

    VIN_EMI (J1) Input voltage to the converter connecting to VIN of the converter through an EMI filter.

    VIN_EMI terminal connects to the input capacitors and the VIN pins of the LM61495-Q1 through an input EMI filter. Connect the supply voltage (battery, bench-top supply, or other supply) between VIN_EMI and GND_EMI connectors. The voltage range should be higher than 3.5 V for the device to start up, and above 3V to continue operation. VIN higher than 6 V provides regulated 5 V output voltage. VIN should be no higher than 36 V to avoid damaging the device. The current limit on the supply must be high enough to provide the needed supply current, otherwise the supply voltage may not maintain the desired voltage. The supply voltage should be connected to the board with short, thick wires to handle the pulsing input current.
    GND_EMI (J1) Ground connection near the input filter.

    This is the current return path for the supply connected to VIN_EMI.
    VOUT (J2) Output voltage of the converter.

    VOUT terminal connects to the power inductor and the output capacitors. Connect the loading device between VOUT and GND connectors on J2 to load the converter output. Connect the loading device to the board with short, thick wires to handle the large DC output current.
    GND (J2) Ground connection near the output.

    This is the current return path for the output voltage connected to VOUT.
    Input Filter Prevents noise from contaminating supply voltage

    The input filter consists of a ferrite bead, filter inductor, and filter capacitors, located on the bottom side of the PCB. The output of the filter is connected to the VIN net, which is connected to the VIN pins of the LM61495-Q1 and the input capacitors.

    Conducted EMI arises from the normal operation of switching circuits. The ON and OFF actions of the power switches generate large discontinuous currents. The discontinuous currents are present at the input side of buck converters. Voltage ripple generated by discontinuous currents can be conducted to the voltage supply of the buck converter via physical contact of the conductors. Without control, excessive input voltage ripple can compromise operation of other devices connected to the source. The input filter helps to smooth out the voltage perturbations leading to the source.
    VIN_S Test point to monitor the input voltage of the device.
    PGND1 Test point for GND reference when measuring VIN_S.
    VOUT_S Test point to monitor the output voltage of the device.
    PGND3 Test point for GND reference when measuring VOUT_S.
    FB Test point for measuring the voltage on the FB pin of the device.
    AGND Test point for AGND reference when measuring FB.
    RT Test point for measuring the voltage on the RT pin of the device.
    RESET Test point for measuring the voltage on the RESET (power good) pin of the device.
    VCC Test point for measuring the voltage on the VCC pin of the device.
    PGND2 Additional GND reference point for test point measurements.
    BIAS jumper (J3)

    Plate the shunt to connect VOUT to BIAS to improve efficiency.
    FB jumper (J4)

    Place the shunt connecting FB and 5V to set VOUT = 5V. Place the shunt connecting FB and 3.3V to set VOUT = 3.3V.
    SPSP jumper (J5) Place the shunt connecting SPSP and OFF to disable spread spectrum. Place the shunt connecting SPSP and ON to enable spread spectrum. Remove the shunt to enable spread spectrum with ripple cancellation.
    MODE/SYNC jumper (J6) Place the shunt connecting MODE/SYNC and AUTO to enable automatic frequency foldback in light loads to improve light load efficiency. Place the shunt connecting MODE/SYNC and FPWM to enable forced FPWM mode to maintain a constant switching frequency regardless of load. Apply a clock signal to the MODE/SYNC pin to synchronize the device to an external clock.
    EN jumper (J7) Place the shunt connecting EN and OFF to disable the device. Place the shunt connecting EN and ON to enable the device. Remove the shunt to enable undervoltage lockout to enable the device when the supply voltage exceeds 6V.