TPS82140: Question about Power Good connection

Satoshi

Guru 19645 points

Part Number: TPS82140

One customer will use power good for LED indicator.

I think that PG sink current is not enough to LED's If, and should to change pullup value, is it correct?

Or, to begin with is these connection not recommended?

Excerpted schematic is attached below;

↓SML-D14MW datasheet

Best regards,

Satoshi

over 5 years ago

0 Gerold Dhanabalan - Online Design Tools over 5 years ago

TI__Genius 14455 points

With this circuit, when you expect the LED to turn on, it will start to draw current from the +5V supply. Even with a 1mA of current drawn by the LED, the voltage drop across the 10k pull up resistor would be 10V, essentially pulling the PGOOD voltage low. You can try driving the gate of the MOSFET with the PGOOD. such that you have a MOSFET switch between the +5V, a current limiting resistor and the LED.

Regards,

Gerold

0 Satoshi over 4 years ago in reply to Gerold Dhanabalan - Online Design Tools

Guru 19645 points

Hi Gerold

Thank you for reply, I understood.

By the way, Is these schematic possibility to damage if not changed to above your advice?

Best regards,

Satoshi

0 Jean Picard over 4 years ago in reply to Satoshi

TI__Intellectual 1125 points

5V is lower than the PG ABS MAX, no damage here.

Also note that in data sheet, PG voltage at < 2mA is specified at 0.3V maximum.

0 Satoshi over 4 years ago in reply to Jean Picard

Guru 19645 points

Hi Jean

Thank you for reply,

I understood that current schematic is no damage, but LED is not as expected operation.

It recommend to change schematic by Gerold's advice.

Best regards,

Satoshi

0 Gerold Dhanabalan - Online Design Tools over 4 years ago in reply to Satoshi

TI__Genius 14455 points

As Jean mentioned, the PG sink current has to be less than 2mA. Which means that max you can have is 2.5k resistor for 5V. But the LED should be able to light up with just 2mA - you need to find an LED that works at such low current.

Regards,

Gerold

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TPS82140: Question about Power Good connection