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About nFault pin of DRV8801

Masami Michino
Genius 5070 points
Other Parts Discussed in Thread: DRV8801

Dear, All

There are the following questions from a customer.
The time of nSLEEP pin is 'Low', nFault pin are described in the data sheet to be a 'not valid'
(9.3.8 Diagnostic Output)
When the output voltage is not decided, may this understand it?
Or should it be understood whether it is 'Low' drive or Open when not decided?

Thanks, Masami M.

  • 0
    TI__Guru** 114905 points
    Hi Michino-san,

    'Not valid' means the nFAULT output may indicate a fault when in sleep mode.

    When entering sleep mode, the nFAULT pin can be either a logic low or logic high. nFAULT should be ignored when the DRV8801 is in sleep mode.
  • 0 in reply to Rick Duncan
    Genius 5070 points

    Hi, Rick Duncan-san,

    Thank you for your reply.
    Customers saw the phenomenon, such as the following.
    When the SLEEP mode, there is a IC that nFault Pin changes at few minutes to 'Low' from 'High', and another IC that nFault Pin changes at a few minutes to 'High' from 'Low'.
    I want to explain it to the customer.
    Please give me advice.

    Thanks, Masami M.

  • 0 in reply to Masami Michino
    TI__Guru** 114905 points
    Hi Michino-san,

    The input to the gate of the nFAULT is floating during sleep. Because of this, the output is unpredictable. It can switch at any time during sleep mode. Low to high transitions can be due to the gate voltage discharging and high to low can be due to coupling in the system.

    If the nFAULT pin is monitored by the mcu, please consider using the internal pullup of the mcu pin connected to the nFAULT pin. When in operational mode, enable the mcu pullup and monitor nFAULT. When in sleep mode disable the pullup, and either enable the mcu pulldown or set the mcu pin as an output low.

    Doing this eliminates current flow through the pullup. When exiting sleep mode, set the mcu pin as an input with the pullup enabled and then exit sleep mode.
  • 0 in reply to Rick Duncan
    Genius 5070 points

    Hi, Rick Duncan-san,

    Thank you very much for your reply.
    I answer it to the customer.

    Thanks, Masami M.