SLVUCS1A july   2023  – august 2023 TPS7H2140-SEP

 

  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 Connection Descriptions
      1. 2.1.1 Connectors
    2. 2.2 Variable Resistors for CS and CL
      1. 2.2.1 Current Sense Resistor
      2. 2.2.2 Current Limit Resistors
    3. 2.3 Open-Load Detection Pull-Up Resistors
    4. 2.4 Connecting Channels In Parallel
  7. 3Implementation Results
    1. 3.1 Separated Output Results
      1. 3.1.1 Power Up and Power Down
      2. 3.1.2 Enable and Disable
      3. 3.1.3 Current Sensing
      4. 3.1.4 Load Step Effects Across Output Channels
      5. 3.1.5 Overcurrent Protection
    2. 3.2 Modified Configuration Results
      1. 3.2.1 Short-to-GND (Fast-Trip) Overcurrent
  8. 4Hardware Design Files
    1. 4.1 Schematic
    2. 4.2 PCB Layouts
    3. 4.3 Bill of Materials
  9. 5Additional Information
    1.     Trademarks
  10. 6Related Documentation
  11. 7Revision History

2.2.2 Current Limit Resistors

  • For the most accurate and detailed guidance, please refer to the Adjustable Current Limit section of the TPS7H2140-SEP data sheet

External resistors are used to convert a proportional load current into a voltage, which is compared with an internal reference voltage. When the voltage on the CL pin exceeds the reference voltage, the output current is clamped.

The inherent current limit (ICL_INTERNAL) is still present when using an external current limit. The smaller value between the internal or external set value decides the actual nominal current limit. If the user decides to not use an external programmable current, then tie the CL pin to ground.

Use Equation 4 and Equation 5 to calculate the value of RCL. The internal band gap voltage, VCL_TH, has a typical value of 0.8 V. KCL (2500) is the output current and the current-limit set value and is constant across temperature and supply voltage.

Equation 4. ICL=VCL_THRCL=IOUT  KCL
Equation 5. RCL=VCL_TH ×KCL  IOUT

The current-limit resistors, R11 and R15 are both 3.01kΩ resistors connected in parallel. Populate/depopulate R11 and R15 to vary CL. When a shunt is inserted in J11, there is no external current limit function, the internal current limit is active.