INA238: Reverse voltage handling / protection

Heiko Berner

Part Number: INA238

We are planning to use the INA238 to measure the input power to a subsystem (typically 28 V).

To make the unit robust we are designing it to be able to survive reverse voltages (for when customer connects power the wrong way round).

From the datasheet the VBUS pin minimum voltage is -0.3 V, so it cannot handle negative voltages.

So my question is whether we can add protection in the form of a diode and / or series resistor to protect this pin against a negative voltage?

regards

Heiko

over 2 years ago

0 Javier Contreras4 over 2 years ago

TI__Mastermind 26485 points

Hello Heiko,

You will need to protect VBUS and VIN+ and VIN- as they cannot go below -0.3V as well and I assume they could go the voltage if connection is reversed. You can add protection diodes but be aware that if they have leakage during normal operation to account for that in the error. If you add resistance be aware going to large to could cause additional error.

Javier Contreras

0 Heiko Berner over 2 years ago in reply to Javier Contreras4

Prodigy 30 points

Thank you for the answer.

Would the circuit below work?

For the VBUS input there will be a small voltage drop in the measurement, but can compensate for that. And the measurement does not have to be very accurate.

Protecting the differential inputs is more difficult. A bit unsure if the diodes and the high input impedance of the pins are going to work together well. And the voltage drop across the two diodes may not match well.

0 Javier Contreras4 over 2 years ago in reply to Heiko Berner

TI__Mastermind 26485 points

Heiko,

That circuit would not work as the diodes would not prevent the voltage at the inputs to go below GND. The diodes in this configuration only prevent the direction of the current. A diode from IN+ which would be your source to GND reverse bias may do the whole job but the diode could get damaged if it cannot provide the current. Normally there is a switch also involved for this. Below are a few resources with different approaches.

https://training.ti.com/reverse-current-protection-101

https://training.ti.com/using-ideal-diodes-reverse-battery-current-protection

https://www.ti.com/lit/an/snoaa23a/snoaa23a.pdf

https://www.ti.com/lit/eb/slyy168/slyy168.pdf

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INA238: Reverse voltage handling / protection