TPS22910A: Pull up for ON pin

Kevin Kachikian1

Part Number: TPS22910A

Hi,

The specs say that the ON pin can not be left floating. In my design I have 3 diodes (anode sides) hooked to the ON pin (which is enabled low). When any of the cathodes of any diode goes to ground, the ON pin drops to ground (or around 0.4v). Thus when all cathodes are not ground (say 3.3v or floating), the ON pin is floating. Therefore a pull-up is needed. What is the highest R pull-up I could get away with yet still satisfy the "no floating" requirement (to minimize current draw)?

Thanks,

Kevin

bard-designs.com

over 3 years ago

0 Shreyas Dmello over 3 years ago

TI__Mastermind 32650 points

Hey Kevin,

TI doesn't spec a max pull-up for this device but we do spec the max leakage of 1uA for the ON pin.

With this leakage, I think a 10kOhm pull up should not cause any concern with the device.

Thank you for choosing TI Power Switches in your designs.

0 Kevin Kachikian1 over 3 years ago in reply to Shreyas Dmello

Prodigy 90 points

Thank You Shreyas. I saw the leakage spec but I didn’t think I could guesstimate/calculate a pull up value using just that information. How did you derive the 10k guesstimation?

Thank You.

0 Shreyas Dmello over 3 years ago in reply to Kevin Kachikian1

TI__Mastermind 32650 points

Hey Kevin,

In the event that the max leakage is flowing into the pin, the voltage (during the pull up state) would only be affected by 0.1V. If I understand you circuit from the way you've defined it, a 0.1V drop should not be sufficient to pull the voltage below the Vih.

I also noted that during the pull down state, current would flow through the resistor and through the diode to GND. By limiting the current here, smaller diodes could be used.

Of course, this is a rough estimation of the system as TI does not spec a max pull up resistance.

0 Kevin Kachikian1 over 3 years ago in reply to Shreyas Dmello

Prodigy 90 points

Thank You Shreyas. I’ll test empirically to see if a threshold can kind of be inferred. Much appreciated!

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TPS22910A: Pull up for ON pin