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TPS1HB16-Q1: Best way to change the current limit by microcontroller/DAC?

Florian Sonnenberger
Prodigy 20 points
Part Number: TPS1HB16-Q1
Other Parts Discussed in Thread: TPS1H100-Q1, TPS25982

What is the best/easiest/cheapest way to have a microcontroller change the current limit of TPS1HB series high-side switches?

The datasheet is not clear what circuit to expect internally at the ILIM pin and the only listed option to set the current limit is by a fixed size resistor between VBB and ILIM.

Ideally we want to have a microcontroller set the current limit of up to 15 high-side switches dynamically based on what an user selects on an HMI screen e.g. from min. 4.4A to max. 22A in ~0.5A steps. The input voltage VBB is different from channel to channel in a range of 6V to 18V.

We only need to change the limit while the output is disabled, however it would be nice if we could change it with output enabled, even if the slope would need to be slow.

I doubt that a DAC can be directly connected to the ILIM pin, so maybe a digital potentiometer as replacement for the resistor could be used, but we'd need a lot of channels which is expensive and our possible voltage range of up to 18V is limiting the choices.

What would you suggest in this situation?

  • 0
    TI__Mastermind 19595 points

    Florian,

    For the TPS1HB16-Q1 the capacitance between the VBB and ILIM pins is going to be very critical here and even trace capacitances in the line from the TPS1HB16-Q1 to the microcontroller would cause the current limit to not behave properly. For this reason for the HB family of high side switches it is not possible to pragmatically/dynamically change the current limit of the devices. For the TPSxHxx family of devices such as the TPS1H100-Q1 (higher RON) it is possible to connect a potentiometer or discrete FET solution to the ILIM pins to dynamically switch between current limits. 

  • 0 in reply to Timothy Logan
    Prodigy 20 points

    Thanks Timothy,

    after some research we found the TPS25982 eFuse, which would also suit our needs quite well.

    Can you tell me if we can use a 1kOhms digital potentiometer between ILIM and GND with the TPS25982?

    What voltages and currents can we expect at the ILIM pin? I'm asking because we need to choose a suitable potentiometer.

    Thank you very much for your support!

  • 0 in reply to Florian Sonnenberger
    TI__Mastermind 19595 points

    I have copied our applications engineer supporting eFuses on here to give more comment. 

  • 0 in reply to Florian Sonnenberger
    TI__Guru 50705 points

    Hi Florian,

    The ILIM pin is a low voltage and current rating pin. The voltage should be less than 5v and current in the 100uA range. Also it is recommended to use the maximum resistance value as 773 ohm so that current limit is greater  than  2A and for better accuracy.

    Regards

    Kunal Goel