TPS92830-Q1: MOSFET Compatibility

Matthew Braden

Part Number: TPS92830-Q1

We have designed a system that leverages a BUK7880-55A to drive multiple arrays of LEDs. When commanded to turn on, the MOSFETs often display unexpected voltage output characteristics.

We have purchased the TPS92830-Q1 EVM eval kit in hopes of resolving these issues by analyzing the characteristics of this board and it's outputs. We noticed this eval kit uses the BUK763R8-80E MOSFETs which are very similar to our selection, but differ in a number of characteristics (see attached comparison below).

Are the BUK7880-55A MOSFETs compatible with the TPS92830-Q1 or do we need to switch our MOSFETs out for something similar to what is used on the eval board?

I have attached a comparison of the MOSFETs below for further examination by TI engineers.

Here is a related thread which did not resolve our issue, but elaborates more on our design, testing and further diagnostic details.

Thank you for your assistance.

mosfetComparison.pdf

over 4 years ago

0 Frank Qiu over 4 years ago

TI__Genius 15776 points

It looks ok, do you connect the LED to test it?

0 Matthew Braden over 4 years ago in reply to Frank Qiu

Prodigy 80 points

Frank Qiu said:

It looks ok, do you connect the LED to test it?

Yes we have an assembled circuit board that has LEDs attached to the outputs.

Initially we set out to drive up to 3A per channel in which we calculated the sense resistor value as:

0.295 mV / 3 A = 0.098 Ω

0 Frank Qiu over 4 years ago in reply to Matthew Braden

TI__Genius 15776 points

i recommend you to do as below step:

1) use 0.098ohm as the sense resistor in our EVM and test whether it can satisfy the output;

2) if it can work, you can reference the EVM's schematic to check whether there are some issue in your desgin,

0 Matthew Braden over 4 years ago in reply to Frank Qiu

Prodigy 80 points

Since our LEDs require a typical current of 50 mA and we have (10 x 5 LEDs in series) for a total of 50 LEDs, our circuit requires 500mA. Our sense resistor value calculation is as follows:

295mV/500mA = 0.59 Ω

After attempting to use this 0.59 Ω resistor value, we are noticing that we get expected output only when the DIAGEN 124k pull-up resistor is absent. Also note that with the 124k pull-up resistor in place, our LEDs do not turn on with expected voltage and output until the VIN is 14 VDC. Why would this be?