TIDT293 October   2022

 

  1.   Description
  2.   Features
  3.   Applications
  4. 1Design Variants
  5. 2Design Overview
    1. 2.1 Board Contents
    2. 2.2 Connector Description
    3. 2.3 User Interface
      1. 2.3.1 Switches and Push-buttons
      2. 2.3.2 Jumpers
      3. 2.3.3 Potentiometers
    4. 2.4 Functional Block Diagram
    5. 2.5 Functional Block Descriptions
  6. 3Features and Performance Curves
    1. 3.1  Test Setup
    2. 3.2  Pulse
    3. 3.3  Levels and Free Run
    4. 3.4  INP
    5. 3.5  Dual-Output Power Supply
    6. 3.6  Overtemperature Protection
    7. 3.7  Slew Rate Adjust
    8. 3.8  Settling Time Adjust
    9. 3.9  Low- and High-Level Adjust
    10. 3.10 Pulse-Width Adjust
    11. 3.11 Period and Delay Adjust
    12. 3.12 Frequency Response
  7. 4Operation
    1. 4.1 Initial Setup – Jumper Selection and Potentiometer Settings
    2. 4.2 Procedure
      1. 4.2.1 Initial Power Up
      2. 4.2.2 Connecting the Circuit Under Test
  8. 5Limitations and Capabilities
    1. 5.1 Wiring Inductance
    2. 5.2 Minimum Voltage
    3. 5.3 Battery Life
  9. 6Typical Failure Mechanism
    1. 6.1 Fast Thermal Failure
    2. 6.2 Slow Thermal Failure

3.6 Overtemperature Protection

The overtemperature protection uses the LM26LVCISD-075, a 75ºC temperature sensor to shut down the driver and load switch. When thermal shutdown occurs, the sensor trips and turns off the driver and load switch circuit by pulling the power-down signal high. The overtemperature LED, D5, turns on to indicate that thermal shutdown has occurred. During thermal recovery, the LED turns off, and normal operation resumes.

For testing a 15-V, 5-A, 66-ms low-level pulse was used. The high-level pulse was set to 25 A at the minimum width of 11 μs. The average power dissipation was 5 W.

Thermal shutdown occurs when the sensor reaches a case temperature of about 67ºC. The thermal plot shows that the FET reaches around 114ºC. The results in the following image use a PSMN008-75B MOSFET in the 125-A, 50-V variant.

GUID-20220531-SS0I-DQGL-B5XC-65X1906ZMVCH-low.png Figure 3-11 LM26LVCISD-075, PSMN008-75B Load Step Board Thermal Shutdown

Thermal recovery occurs at a lower temperature of about 63ºC. The thermal plot shows that the FET reaches around 94ºC. The results in the following image use a PSMN008-75B MOSFET in the 125-A, 50-V variant.

GUID-20220531-SS0I-RTHL-KVWS-37N76V61RPJ3-low.png Figure 3-12 LM26LVCISD-075, PSMN008-75B Load Step Board Thermal Recovery