3 Test Setup and Conditions

For the tests done below, a resistive load was placed in parallel with the capacitive load. The load current (I_LOAD = I_L) was set to half of the externally set current limit.

This experiment evaluates how the current limit (MIN – CL lower limit, TYP – CL midpoint, MAX – CL upper limit) and temperature (25°C, 85°C) affect the ability of the switch to successfully charge capacitive loads.

Equipment:

• TI EVMs – TPS1HTC30EVM & TPS1HTC100EVM

• E-load in constant resistance mode

• Function generator – 3.3V DC signal

• Power supply – 48V

• Electrolytic capacitors (rated 50V or higher)

• Temperature chamber (85°C)

• 0805 surface mount resistors (10kΩ, 16.7kΩ, 20kΩ, 50kΩ)

  Note: 51kΩ was used since 50kΩ was not readily available.

• Cables

• Voltage and current probes

• Safety box or enclosure (optional)

To eliminate any unwanted or abnormal behavior occurring with TI’s HSSs, make sure to use the e-load in constant resistance mode. Constant current mode does not accurately depict the behavior of a purely resistive load because the load is always constantly drawing a preset current. Refer to (+) [FAQ] Why does my e-load cause my high side switch to shut down? - Power management forum - Power management - TI E2E support forums for more information.

When using an e-load, unless the resistive load is actively on, the device detects an open-load fault. For each test, the following were the sequence of steps followed:

1. Connect electrolytic capacitor on the output in parallel with the resistive load. The anode or positive (longer) lead was connected to power and cathode or negative (shorter) lead to ground.

2. Turn on the e-load after configuring the appropriate resistance for the current limit being tested.

3. Turn on the input power supply to be in a high and stable condition.

4. Trigger the 3.3V EN high signal using the function generator.

5. Note the results and turn off the power supplies.