TPS40210-Q1: TPS40210-Q1 RC pin state at disable

Tomohiro Nagasawa58

Expert 1570 points

Part Number: TPS40210-Q1
Other Parts Discussed in Thread: TPS40210

Dear support team

Could you teach the state of the RC pin when TPS40210-Q1 is disabled?

(Pull-down or High-Z?)

Regards

Tomohiro Nagasawa

over 7 years ago

0 Garrett Roecker over 7 years ago

TI__Mastermind 21720 points

Hello Tomohiro,

When the TPS40210 is disabled the RC pin is in a high impedance state. There is no internal pull down on the pin.

Thanks,

Garrett

0 Tomohiro Nagasawa58 over 7 years ago in reply to Garrett Roecker

Expert 1570 points

Garrett-san

Thank you for response.

In the case of the High-Z state It seems that 10 V or more voltage is applied to the RC pin when disabled, is there the problem of destruction?

(Absolute maximam voltage of RC pin is 10V in datasheet.)

Regards

Tomohiro Nagasawa

0 Garrett Roecker over 7 years ago in reply to Tomohiro Nagasawa58

TI__Mastermind 21720 points

Hi Tomohiro,

The RC pin should be clamped below the specified absolute maximum voltage to ensure that the device is not damaged. The can be done with an external zener diode.

Thanks,

Garrett

0 Tomohiro Nagasawa58 over 7 years ago in reply to Garrett Roecker

Expert 1570 points

Hello Garrett-san

Thank you for quick response.

Do you mean that an external clamp diode is required for applications with Vin> 10 V?

Regards

Tomohiro Nagasawa

0 Garrett Roecker over 7 years ago in reply to Tomohiro Nagasawa58

TI__Mastermind 21720 points

Hi Tomohiro,

It is suggested to have an external clamp diode on the RC pin for when the VDD rail is above 10V. If no external zener diode is uses the ESD protection structure will clamp the voltage. To keep the ESD structure from clamping the Zener should be used. Note the ESD structure can sink some current (~50mA) and be okay.

Thanks,

Garrett

0 Tomohiro Nagasawa58 over 7 years ago in reply to Garrett Roecker

Expert 1570 points

Hello Garrett-san

Thank you for response.
If no external zener is used, what is the clamp voltage of ESD protection structure?
And what is the resistance value between the Vdd and RC pins required for the internal clamp structure to work?

Regards
Tomohiro Nagasawa

0 Garrett Roecker over 7 years ago in reply to Tomohiro Nagasawa58

TI__Mastermind 21720 points

Hello Tomohiro,

The resistor can just be selected to keep the current below 50mA. For example, R = (VINmax-10V)/50mA, this should provide a resistance value that will limit the current into the pin. This might not be reasonable for the switching frequency that has been chossen. In this case I would recommend using the zener clamp diode to protect the ESD circuity.

Thanks,

Garrett

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TPS40210-Q1: TPS40210-Q1 RC pin state at disable