SNVU893 March   2025

 

  1.   1
  2.   Description
  3.   Features
  4.   4
  5. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  6. 2Hardware
    1. 2.1 Additional Images
    2. 2.2 Power Requirements
    3. 2.3 Setup and Operation
  7. 3Implementation Results
    1. 3.1 Evaluation Setup
    2. 3.2 Performance Data and Results
  8. 4Hardware Design Files
    1. 4.1 Schematics
    2. 4.2 PCB Layouts
    3. 4.3 Bill of Materials (BOM)
  9. 5Additional Information
    1. 5.1 Trademarks

2.3 Setup and Operation

This section describes the connectors, test points, and jumpers on the EVM and how to properly connect, set up, and use the LM65635EVM See Figure 2-3 for location of connectors and jumpers and typical setup.

    VOUTOutput voltage of the converter.VOUT banana post. Apply load to this connector.
    VOUTS The VOUTS test point is used to monitor output voltage.
    GNDS Test point next to VOUTS test point. This GNDS test point is use as the negative DMM connection for VOUT sensing.
    VINInput voltage to the converter.VIN banana post. Apply input voltage to this connector.
    VINS The VINS test point is used to monitor input voltage.
    GNDS Test point next to VINS test point. This GNDS test point is use as the negative DMM connection for VIN sensing.
    GND Ground of the converter GND banana posts. Apply load ground and input voltage ground to these connectors. The various GND test point are used as ground sense for input voltage and output voltage measurements.
    ENThe use of the EN jumper is self-explanatory. To supply an external signal to the EN input of the device, remove the EN jumper shunt and apply the signal to the EN test point. To use the external UVLO feature, populate Rent (R3) and Renb (R4) as desired and remove the EN jumper shunt. Note that for accurate shutdown current measurement, these resistors must be removed (if used) and the EN jumper shunt moved to "OFF".
    RTThe RT jumper is used to select the switching frequency and is self explanatory.The default inductor on the EVM is designed for 2.2MHz operation. Other frequencies require a different value of inductance. To adjust the switching frequency, remove the RT jumper shunt and populate RT (R5) with the desired value. See the LM656x5 data sheet for frequency vs. RT resistor value.
    MODEMODE jumper is used to select the operating mode of the device. With MODE in the AUTO position, the device operates in automatic PFM/FPWM mode depending on load current. With the MODE in the FPWM position, the device operates at fixed frequency for all load currents.The MODE pin is also the frequency synchronization input. To synchronize the device to an external clock, remove the MODE jumper shunt and apply the clock to the MODE test point.
    Feed-back Connections The EVM is set for a fixed 5V output, with Rfbt2 (R7), 0Ω, populated. To set the output voltage to 3.3V, remove Rfbt2 (R7) and populate Rfbb (R10) with a 0Ω resistor. To use the adjustable output voltage option, populate Rfbt (R9) and Rfbb (R10) with the appropriate value resistors. Rinj (R8) must also be populated with a 10Ω to 50Ω resistor. The reference voltage is 0.8V. See the LM656x5-Q1 High Performance Power Converter, 3V to 65V, Pin-Compatible, 2.5A/3.5A/4.5A, Automotive, Low EMI Synchronous Buck Converter data sheet for appropriate values of feed-back resistors. When using the adjustable output voltage mode, a Bode plot can be taken using the Rinj (R8) resistor. This resistor becomes the injection point for the frequency response analyzer, allowing the loop frequency response to be taken in the usual way. In the fixed output voltage mode, a Bode plot can not be taken.
    PGOODThe PGOOD test point is used to monitor the power-good indicator. This flag indicates whether the output voltage has reached the regulation level. PGOOD is an open-drain output that is tied to VOUT through a 100kΩ, resistor, Rpg (R1).
    VCC VCC Test point The VCC pin is the output of the internal LDO. The VCC voltage is typically 3.3V. This point can be used for logic inputs and/or pull-up. Do not connect to external loads.
    BIAS Auxiliary input to LDO Connected to VOUT through 0Ω Rbias (R11) on EVM. To change the input supply of the LDO, remove Rbias (R11) and connect external supply to BIAS pin, or ground BIAS pin as required. Populate Cbias (C11) when using an external bias supply. See the LM656x5 data sheet for more information.
    Bode Plot When using the adjustable output voltage mode, a bode plot can be taken using the connection shown in Figure 2-4. Rinj (R8) must be populated.
    EMI Filter The EMI filter is not populated on the EVM. To test the EMI filter, components L2, C1 and C2 must be populated, while R12 must be removed. Typical values of these components are given in Section 4.3.
LM65635EVM LM65635EVM Setup Figure 2-3 LM65635EVM Setup
LM65635EVM LM65635EVM Loop Response Connections Figure 2-4 LM65635EVM Loop Response Connections