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BQ79616-Q1: BAT pin filter

James Gormley
Prodigy 85 points
Part Number: BQ79616-Q1

Hello,

It is my understanding that the RC values given in the datasheet and design guide were specifically selected and optimized for ESD and hotplug protection.  I also understand that it is recommended to strictly follow those guidelines.  For non ESD and non hotplug reasons we would like to increase the filter on the BAT pin.  Is there any flexibility in increasing the BAT pin filter cap?  Is there a relationship that if we change the BAT pin cap then the other RC filters also need changed? 

Thanks.

  • 0
    TI__Intellectual 1845 points

    Hi James,

    You are understanding correctly. The BAT filter cap is mainly there for hotplug reasons to pass voltage spikes to ground in the case of a hotplug event. If you are using the '616 for non-hotplug applications I see no issue to increase the BAT filter cap. The RC filter on the BAT pin is independent of the other RC filters so I do not see a need to change the values of other capacitors on other pins.

    Thanks,

    Chase

  • 0 in reply to Chase Fagen
    Prodigy 85 points

    Chase,  We are using the '616 in an application where it will be hot plugged.  Our concern is after the hotplug event and during normal operation we expect some transients on the BAT pin.  We would like to increase the RC (30 Ohm, 0.01uF) BAT pin cap to filter those transients.  The voltage sense filters are already sufficient. By changing the 0.01uF we don't want to ruin our hotplug and/or ESD protection.  We are trying to address the transients in other ways but were hoping for extra protection.  So in the situation where hotplug and ESD protection are needed is there any flexibility in increasing the BAT pin cap?

  • 0 in reply to James Gormley
    TI__Intellectual 1845 points

    Hi James,

    The recommended values for the BAT resistor and capacitor were tested on our end and configured for a specific cutoff frequency for hotplugging events and to take in account any transients from the hotplugging event. Therefore it is not recommended to change the values of the resistor and capacitor since they were already tested for that purpose. 

  • +1 in reply to Chase Fagen
    Prodigy 85 points

    OK, Thanks!  That is what I thought but was just checking.