SLVUCB8A May   2022  – September 2022 TPS25985

 

  1.   TPS25985 evaluation module for eFuse User's Guide
  2.   Trademarks
  3. 1Introduction
    1. 1.1 EVM Features
    2. 1.2 EVM Applications
  4. 2Description
  5. 3Schematic
  6. 4General Configurations
    1. 4.1 Physical Access
    2. 4.2 Test Equipment and Setup
      1. 4.2.1 Power supplies
      2. 4.2.2 Meters
      3. 4.2.3 Oscilloscope
      4. 4.2.4 Loads
  7. 5Test Setup and Procedures
    1. 5.1  Hot Plug
    2. 5.2  Start-up with Enable
    3. 5.3  Difference Between Current Limit and DVDT Based Start-up Mechanisms
    4. 5.4  Power-up into Short
    5. 5.5  Overvoltage Lockout
    6. 5.6  Transient Overload Performance
    7. 5.7  Overcurrent Event
    8. 5.8  Provision to Apply Load Transient and Overcurrent Event Using an Onboard Switching Circuit
    9. 5.9  Output Hot Short
    10. 5.10 PROCHOT# Implementation Using General-Purpose Comparator
    11. 5.11 Quick Output Discharge (QOD)
    12. 5.12 Thermal Performance of TPS25985EVM
  8. 6EVAL Board Assembly Drawings and Layout Guidelines
    1. 6.1 PCB Drawings
  9. 7Bill Of Materials (BOM)
  10. 8Revision History

5.8 Provision to Apply Load Transient and Overcurrent Event Using an Onboard Switching Circuit

The TPS25985EVM provides an add-on circuit to facilitate load transients and persistent overcurrent events. The implementation consists of three (3) low side MOSFETs (Q7, Q8, and Q9) and a monoshot gate driver circuit (U5 and U6) as well as six (6) onboard load resistors of 1 ohm each (R28 to R33) in parallel. Using a single pole single through (SPST) switch (S1), the monoshot gate driver generates a gate signal of 1 ms, 2 ms, 5 ms, 10 ms, and 20 ms durations. By doing this, the low side MOSFETs (Q7, Q8, and Q9) are turned on for that specific duration, creating a load transient in addition to the steady-state load. Use the following instructions to apply a load transient or persistent overcurrent event using this onboard switching circuit:

  1. Configure the Jumper J3 to an appropriate position to obtain required overcurrent blanking period (tTIMER) as per Table 4-3.

  2. Configure the Jumper J6 position to desired reference voltage for overcurrent protection and active current sharing as mentioned in Table 4-3.

  3. Configure the Jumper J4 in a suitable position to set required circuit breaker threshold (IOCP) as per Table 4-3.

  4. Set the input supply voltage VIN to 12 V and current limit to 200 A.

  5. Connect the power supply between VIN (Connector T1) and PGND (Connector T3) and enable the power supply.

  6. Connect a steady state load between VOUT (Connector T2) and PGND (Connector T3).

  7. Use the single pole single through (SPST) switch (S1) to configure the transient load turn on duration.

  8. Press the switch SW3 to turn on the Q7, Q8, and Q9 MOSFETs, which creates a load transient of 72 A (typical) between VOUT and PGND with 12 V output.

  9. Observe the waveforms of VOUT (TP4), MOSFET GATE (J9), and input current using an oscilloscope.

Another option is to apply a custom load transient using an external function generator, connected between TP38 and TP39, and the shunt of jumper J9 set to "2-3".

CAUTION:

In that case, make sure to limit the transient load current magnitude to a safe level for reliable operation of the load resistors (R28 to R33) based on their maximum permissible peak pulse power vs pulse duration plot.

Figure 5-13 and Figure 5-14 show the test waveforms of transient overload and persistent overload events respectively using the onboard switching circuit.

Figure 5-13 Transient Overload Performance in TPS25985EVM Using the Onboard Switching Circuit (VIN = 12 V, CITIMER = 22 nF, COUT = 470 μF, RIMON = 1.1 ∥ 1.1 kΩ, RIREF = 40.2 kΩ, IOUT(Steady-State) = 100 A, and IOUT(Transient) = 69 A for 9 ms)
Figure 5-14 Persistent Overload Performance in TPS25985EVM Using the Onboard Switching Circuit (VIN = 12 V, CITIMER = 22 nF, COUT = 470 μF, RIMON = 1.1 ∥ 1.1 kΩ, RIREF = 40.2 kΩ, IOUT(Steady-State) = 100 A, and IOUT(Transient) = 69 A for 18 ms)