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Input protection

John Ford
Intellectual 530 points
Part Number: DRV8210
Other Parts Discussed in Thread: TPS54201

Hi.

I'm using the DRV8210DSG as a static switching H bridge in conjunction with a tps54201 as a bidirectional TEC driver.  Since the DRV8210 is on the high side of the current sense resistor, it is subject to up to a 1V transient in case of a short circuit in my load, 

In order to protect the PH input, I was going to put in a small diode to clamp the voltage between the input and the GND to one diode drop.  So if my control input is high, the pin will have ~3.3 V on it, and all is well.  If the control input is low, the diode will conduct when the pin goes below the GND level, which is at a positive ~1V.    See the diagram.  Does this seem like it will work for this purpose?

Thanks!

John

  • 0
    TI__Mastermind 37683 points

    Hi John,

    Where exactly is the 1V transient occurring? Is it at the VM supply of the driver or on the control pins?

    Can you also clarify how the DRV8210 and the tps part are connected. Is it not vlear from the schematic you showed. If you don't want to share the schematic that is alright. A simple block diagram will work.

    One issue I can see from the schematic is the GND pin of the driver is not connected directly to the common GND. This is okay to do, as we show an example of a sense resistor from GND pin to common GND for current sensing in the datasheet. However, the voltage of the device GND with respect to common GND should not exceed more than 0.5V.

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    Intellectual 530 points

    Hi Pablo.  The 1 V transient would be in case of an overload condition.  The sense resistor, in normal operation, will max out at 200 mV, but if a short occurs in the load, the extra current could cause up to a 1V transient before the TPS54201 shuts down.  I was concerned about the ground pin going to 1V while my logic is driving the EN input to the common GND, which violates the 0.5V limit.  My thought was that since I am driving the EN pin through a 10K resistor, the diode would clamp the EN pin to the GND with one diode drop, which for this diode is ~ 340 mv.  I've attached the whole schematic page for clarity. 

    12tecrevbP2.pdf

  • 0 in reply to John Ford
    Intellectual 530 points

    I should have had more coffee before posting!  Clearly, I should have said the PH pin, not the EN pin.

  • +1 in reply to John Ford
    TI__Mastermind 37683 points

    Hi John,

    Thank you for the explanation. It's clear to me now.

    The clamping diode is okay to use as long as it clamps the voltage to below 0.5V.

    Regards,

    Pablo Armet