ISO5851: Fault Pin Always Low

Gordon Marshall

Prodigy 50 points

Part Number: ISO5851

Hey Team,

I'm using ISO5851 Gate drivers in a 3kW inverter application for a university project.

The gate driver is always low on the fault pin which cannot be reset with a Low input to the fault reset pin.

The operating condition on the logic side of the component is 3.3V referenced to 0V of the microcontroller.

On the driver side VCC is +20V while Vee is -5, Ideal for driving SiC components.

With this in mind I assume that UVLO is not the root cause of the fault.

The Desat Pin has been isolated from the circuit with the voltage at 0 with respect to GND2 yet the fault persists.

Any help here would be Greatly appreciated.

I have attached a Schematic of the Gate Driver circuitry below.

over 3 years ago

0 Wei Zhang over 3 years ago

TI__Intellectual 2061 points

Hello Gordon, Thanks very much for your questions.

Can you please help me understand:

1. what is VCC1?

2. What is IN+ and IN-referenced to GND1?

3. Can you please help share your schematic?

Thanks very much.

Wei

0 Gordon Marshall over 3 years ago in reply to Wei Zhang

Prodigy 50 points

Hey Wei,

As mentioned in the previous post the logic side vcc1 is referenced to 3.3V

In+ is 3.3V

In- is Gnd

The schematic is attached to the original post.

Thanks

0 Gordon Marshall over 3 years ago in reply to Gordon Marshall

Prodigy 50 points

0 Gordon Marshall over 3 years ago in reply to Wei Zhang

Prodigy 50 points

0 Wei Zhang over 3 years ago in reply to Gordon Marshall

TI__Intellectual 2061 points

Hello Gordon, Thanks very much for your feedback.

I cannot see the attachment in the original post. You can attach it by adding an attachment. The copy/paste image doesn't work well.

Can you please help check and let me know every pin status, high or low or voltage conditions?

Another try is to try a brand-new part? and to make sure there is no random damage.

We will try our best to help you debug from there.

Wei

0 Wei Zhang over 3 years ago in reply to Wei Zhang

TI__Intellectual 2061 points

Thanks for the schematic.

Can I confirm my understanding that the Desat port is shorted to GND2?

Can you please help check and let me know every pin status, high or low or voltage conditions?

Can you help monitor the current consumption? is the chip hot? Another try is to try a brand-new part? and to make sure there is no random damage.

It is strongly recommended to add bypassing capacitance on IN+, IN-, Rdy, FLT and RST all in put pins from 100pF to 1nF and close to the pin to increase the noise immunity under noisy environment.

Thanks. Look forward to your feedback.

Wei

0 Gordon Marshall over 3 years ago in reply to Wei Zhang

Prodigy 50 points

Hey Wei,

Thanks for the reply.

This is a brand new chip on the PCB.

I have diagnosed further and the fault pin can be reset when there is no input to the in+ pin.

As soon as a driving voltage is applied to in+ the fault pin is set low.

Logic side

In- 0V

Ready pin is high

FLT reset high

VCC 3.3V

GND1 0V.

FET side.

VCC = 20V

Vee = -5

GND2 = 0V

out = -5

Desat = 0.8V

0 Wei Zhang over 3 years ago in reply to Gordon Marshall

TI__Intellectual 2061 points

Hello Gordan,

It sounds like there are some simple stuff we are missing or there are something very challenging. I will reach to the team, discuss and get back to you when we have further clue. Thanks very much for your patience.

Wei

0 Gangyao Wang over 3 years ago in reply to Gordon Marshall

TI__Prodigy 645 points

Hi Gordan,

How DESAT signal (pin 1 of D1 in the schematic) is connected? If it is floating (not connected), you will have a DESAT fault for every turn on. If you are not connecting an IGBT or MOSFET, you can short this to GND2 to avoid DESAT fault triggering.

Regards,

Gangyao

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ISO5851: Fault Pin Always Low