TPS2121: ST pin not reporting correct value

Ashish Goel

Prodigy 40 points

Part Number: TPS2121

The voltage is 0.0 V when IN2 is active. (This is as expected)

The voltage at pin PWR_MUX_ST is 0.78V when IN1 is active. (I expect it to be 5V)

Can anyone help as to what could be the reason?

Thanks,

Ashish

over 5 years ago

0 Ashish Goel over 5 years ago

Prodigy 40 points

Ashish Goel said:

Part Number: TPS2121

The voltage at pin PWR_MUX_ST is 0.0 V when IN2 is active. (This is as expected)

The voltage at pin PWR_MUX_ST is 0.78V when IN1 is active. (I expect it to be 5V)

Can anyone help as to what could be the reason?

Thanks,

Ashish

0 Shreyas Dmello over 5 years ago in reply to Ashish Goel

TI__Mastermind 32650 points

Hi Ashish,

Please share a scopeshot of this switchover and the voltage on the ST pin. Where is the 5V being source from?

The ST pin is an open drain FET which means that when IN1 is selected, the device will output high-z on this pin. If 5V is not seen on this pin, that means there is a secondary path to ground which is resulting in a voltage division.

Is this event occurring over multiple devices?

0 Ashish Goel over 5 years ago in reply to Shreyas Dmello

Prodigy 40 points

Hey Shreyas,

Thank you for your reply and help. Yes it looks like it was a secondary path issue.

The pin is behaving properly as expected now.

Thank You.

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TPS2121: ST pin not reporting correct value