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Original question:

Strange behavior of TPS3705-33 when MR input is exposed

TPS3705: Issue with MR signal line causing unwanted resets

Jeril Jose
Prodigy 160 points
Part Number: TPS3705

Hi I have observed noises in MR signal during system ESD testing ( ESD applied to the equipment which employs TPS3705 for reset purpose). Due to the noise induced in supply rails, I could see this IC causing reset to the system. I did observe the IC getting reset if I just tap on the /MR pin while connecting the oscilloscope pin as well. Why is this issue happening? Is this a problem with sensitivity of the/MR pin?

Is there timing requirement for /MR signal?

I am planning to put a bypass capacitor near the /MR pin. Will it cause any timing issue with respect to reset? What value would be recommended?

I dont see any information related to this in the IC datasheet.

  • 0
    TI__Genius 12630 points
    Jeril,

    If /MR goes to logic low (0.3 x VDD or less) for longer than 100ns, then the /RESET should trigger to active low. Can you provide a scope capture with the VDD, /MR and /RESET pins? Please send scope captures to michaeldesando@ti.com

    /MR is also internally pulled up by 14kohm pull-up resistor to VDD so if VDD is experiencing significant noise, this could also lead to /MR causing a reset.


    -Michael