TPS79101 behavior during ESD

Ravindranath Radhakrishnan1

Other Parts Discussed in Thread: STRIKE

Hi,

We are using TPS79101 in our board to generate 3.1 Volts. The input to the TPS79101 is from the Battery charger circuit (BQ24075TRGT). The output of the TPS79101 is used to power an MSP430 and an capsense controller.

When we apply a +/-4KV ESD pulse to the input of the battery charger circuit which has a ESD diode (PESD5V0X1UAB) placed we could see the output of the TPS79101 will become 1.5 Volts instead of 3.1 Volts.

The schematics of TPS79101 is as below.

Request your inputs on this.

Regards

Ravindranath R

over 9 years ago

0 Ryan Eslinger over 9 years ago

TI__Guru 55940 points

Hi Ravindranath,

Could you please provide a scopeshot of the input voltage and output voltage of the LDO both before and after the ESD strike?

Very Respectfully,

Ryan

0 Ravindranath Radhakrishnan1 over 9 years ago in reply to Ryan Eslinger

Prodigy 135 points

Hi Ryan,

Thanks for the reply.

We were not able to capture the voltage levels during the ESD testing. We measured the voltage using a multimeter. The input will be the battery voltage (3.7~4.0 Volts) that has not changed after the ESD pulse but the output dropped to 1.5Volts. It recovers once we remove the battery and put it back.

Is there a possibility of any Latchup in the microcontroller or the capsense controller during ESD.

Regards

Ravindranath

0 Ravindranath Radhakrishnan1 over 9 years ago in reply to Ravindranath Radhakrishnan1

Prodigy 135 points

Hi Ryan,

Another observation missed to mention is that when we put 100Ohms resistor in place of S5 (0 ohm) we could see the output voltage comes back to 3.1 Volts.

Regards

Ravindranath

0 Ryan Eslinger over 9 years ago in reply to Ravindranath Radhakrishnan1

TI__Guru 55940 points

Hi Ravindranath,

The recovery after replacing the resistor makes it sound like something downstream from the LDO may be biasing the output voltage. It is important to check the ESD ratings for all of the ICs. For example, TPS79101 has an absolute maximum ESD rating of 2kV.

Very Respectfully,

Ryan

0 Ravindranath Radhakrishnan1 over 9 years ago in reply to Ryan Eslinger

Prodigy 135 points

Hi Ryan,

Thanks for the input. The output of the LDO is connected to an MSP430F2212 and an Capsense controller. When we disconnected the keypad controller we didn't see the problem.So yes its the problem with the capsense controller.

Regards

Ravindranath R

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TPS79101 behavior during ESD