TPS28225: Help to check internal resistor between pin4 and pin5.

Hi Helios,

Thanks for your field support. My name is Mamadou Diallo, I will help address your concerns.

What values are your customers measuring? What do you mean by "varying a lot"?

Thanks in advance for providing those details.

Regards,

-Mamadou

Hi Mamadou,
This is Duncan for Quanta EE RD.

This problem occurs at flying probe test in the production process of our products.
The flying probe will measure the external resistor (100k ohm) on pin5 (LGATE) through ground.
The measured value of most boards is 100K ohm, but only one PCBA is 23.34K ohm.
TI also helped analyze (V-I curve) the IC, and the result is no problem.
So we guess that there should be resistance to ground inside LGATE, and What is the resistance value?
And should we modify our measurement specifications?

BR
Duncan

Suggest as Answer

Hi Duncan,

Glad to hear back from you. Which datasheet did you find that block diagram attached on your first post?

It seems odd since I am looking at TPS28225's datasheet and as you can see below, we do not specify a resistor between pin 4 and pin 5 and even more puzzling is the fact that you're measuring a 100kohm resistance between the 2 pins. 

The picture below is from the following link:

www.ti.com/.../tps28225.pdf

 But that resistor would only be there to prevent any open-gate conditions and any accidental turn on during output active low events on the power FET. 

It can also be set externally by simply connecting the desired resistance value from pin 5 to ground.

What application and in what topology are they using the device that the customer is concerned?

Thanks.

Regards,

Hi Mamadou,
Sorry, the part number we use is TPS28225-Q1 (for automotive), Not TPS28225 (for consumer).
datasheet link : www.ti.com/.../tps28225-q1.pdf
thanks

Hi Duncan,

Thanks for clarifying that. I don't believe there is any need to modify any measurements specifications.

How many devices did they test that resulted in the resistor being 100 kohm.
Is the customer not sure whether the actual value should be 100 kohm?
I would suspect the 23.34 kohm reading from the one device to be an off/error.

I will order samples which takes about 2-3 business days to ship and measure on the bench and I will get back to you by COB next week on Thursday (Dallas time).

Thanks for your patience.

Regards,

-Mamadou

Hi Mamadou,

below list to show the resistance between the pin4 and pin5 of TPS28225-Q1.

Sample1 (call "NG sample"):

The resistance is 85.7K.

Sample2 (call "NG sample"):

The resistance is 270K.

Sample3 (call "Good sample")

The resistance is 1.8M.

And please help to the difference on the marking.

1. NG sample : PXND TI 75K 0708

2. Good sample : PXND TI 6CK AGHF

thanks