• TI Thinks Resolved

TPS3809: if /MR is pulled low during tpd(r), does /Reset low time keep same or increase?

Part Number: TPS3809

Hi,

if /MR is pulled low during tpd(r), does /Reset low time keep same or increase?

  • Max,

    If /MR is pulled low DURING t_PD(r) then /RESET will go low after td(MR). If /MR is pulled low after the device is already about to RESET due to sense input, then /MR is ignored.

    -Michael

  • In reply to Michael DeSando1:

    Hi Michael,

    thanks.

    my requirement: when I pull a pin low and then release it, /RESET pin will go low 10s and then go high, during /RESET low status, this pin is ignored, no matter it is pulled high or low.

    do you know which device can meet this requirement?

  • In reply to Max Han:

    Max,

    Yes, we have several devices that do exactly that. My recommendation is TPS3890. You can also use TPS3808, TPS389x (TPS3895, TPS3896, TPS3897, TPS3898). These devices differ in output type (active low/active high, open drain/push pull) and if you require automotive grade. The key for your application is that the device is "programmable" to 10 seconds which all of these device are. If you need additional support please let me know!

    -Michael

  • In reply to Michael DeSando1:

    Hi Michael,
    the key information is that:
    during /RESET low status, /MR pin is ignored, no matter it is pulled high or low, the /RESET only keep tPD(r).
    does TPS389x meet this requirement?

  • In reply to Max Han:

    Max,

    Not quite. For TPS389x family, the /ENABLE pin needs to be asserted (in low state) for the output to function. If the device resets and /ENABLE is still high, the output is disabled and will remain in high state.

    For TPS3808 it is similar but the pin is called /MR so that /MR needs to be high for the output to function. If /MR is low, the device will remain in reset condition.

    It is possible to use these devices without utilizing the ENABLE/MR features by tying them to the respective voltages needed to keep the devices enabled. In that case, they won't affect the /RESET output signals since they will always have the output enabled.

    -Michael