SLVU777A September   2012  – November 2021 TPS54020

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Background
    2. 1.2 Performance Specification Summary
    3. 1.3 Modifications
      1. 1.3.1 Output Voltage Setpoint
      2. 1.3.2 Slow-Start Time
      3. 1.3.3 Adjustable UVLO
      4. 1.3.4 Input Voltage Rails
  3. 2Test Setup and Results
    1. 2.1  Input / Output Connections
    2. 2.2  Efficiency
    3. 2.3  Output Voltage Load Regulation
    4. 2.4  Output Voltage Line Regulation
    5. 2.5  Load Transient
    6. 2.6  Control Loop Response
    7. 2.7  Output Voltage Ripple
    8. 2.8  Input Voltage Ripple
    9. 2.9  Start Up
    10. 2.10 Pre-Bias Start Up
    11. 2.11 Hiccup Mode Current Limit
  4. 3Board Layout
    1. 3.1 Layout
  5. 4Schematic and Bill of Materials
    1. 4.1 Schematic
    2. 4.2 Bill of Materials
  6. 5Revision History

1.3.3 Adjustable UVLO

The undervoltage lockout (UVLO) is adjusted externally using R6 and R11. The EVM is set for a start voltage of 7.5 V and a stop voltage of 7.1 V using R6 = 69.8 kΩ and R11 = 13.3 kΩ. Use Equation 3 and Equation 4 to calculate required resistor values for different start and stop voltages.

Equation 3. GUID-7F66CF9B-F2CB-47D1-A346-AEA2DF4E9566-low.gif

Equation 4. GUID-928F6BCF-8E04-4151-A909-15FE622CE637-low.gif

Where:

VariableDescriptionNominal Value
VStartDesired start voltageAs desired, but must be greater than 4.4 V
VStopDesired stop voltageAs desired, but must be greater than 4.2 V
VEN fallingEnable pin stop threshold voltage1.17-V nominal
VEN risingEnable pin start threshold voltage1.21-V nominal
IpEnable pin source current while OFF1.15-µA nominal
IhEnable pin hysteresis current2.15-µA nominal