TMCS1101: The A3U Output is 100mV/A

Gianrico,

This is certainly odd behavior, as the sensitivity of any A3 units should be 200mV/A as you say. Just to verify, can you share the test method you are employing to determine this, as well as a schematic of your setup?

Hi Carolus, thank you for the answer.

The A3 is soldered on the PCB in position U106. C131 was removed. Power supply is 5V

Simply I measured the output at TP102 without any connection to J106/J110: 500mV

Then I supply a 1A/2A/3A current by a Bench supply and an electronic load: 600/700/800 mV at output.

Now I bought the A2 and the A4 version to check what's happen...

Gianrico,

Thanks for sharing. The schematic leads me to a few additional follow-up questions here:

- You are feeding the output of the TMCS1101 into a LPF where the capacitance selected is 1uF. However, the maximum output capacitance the device is capable of supporting is only 1nF. It could be that the device is becoming unstable due to not enough isolation resistance on the output. Have you tried increasing the 100Ω and seeing if this results in any change in behavior?

- Where are you observing the incorrect gain? Are you probing the actual device, are are you reading this off of the terminal/GUI of your connected ADC? 

Carolus, 

I had your same doubt; for that reason I removed the 100 Ohm resistor so the output of A3 is floating.

I measured at TP102 (A3 output) with a DMM and then I checked with an oscilloscope for noise/instability: the result is the same, 100mV/A...

Now I wait for A2 and A4 samples to do some tests.

Regards

Gianrico, 

Thanks for the confirmation. Please keep me posted as you run further tests. 

Today I've tested a new A2/A3/A4 samples from DigiKey (see image).

The A2 is 100mV/A

The A3 is 100mV/A

The A4 is 400 mV/A

It seems that a wrong or fake lot of this part is circulating in the market.

If you want I can send the samples to you for further testing.

And if possible, to receive some samples directly from Texas.

I am here for any other information or test.

Regards

Gianrico,

Is it possible to get a screenshot of the top of the original sample(s) from Mouser? Or a similar shot of the label from the bag the parts came in? Also, I will reach out with a friend request. I may ask to see if I can receive these from you for analysis. I can also see about getting some fresh samples sent to you. 

Carolus, next Tuesday I'll be in the lab and take the screenshots. I can deliver all the samples to you, let me know how to do this.

Yesterday I did the Last Chance Test... (see photos).

Here the pictures of the components

.

gianrico,

Thanks for the above information. I have reached out to you via private message with my contact information to send these to me. We can also try and arrange some fresh samples if you are interested if we can find some in stock.

Ok I'll send to you all the samples I have. If I can have fresh samples it is ok but my real problem is the availability of the component, I need 500/1k pieces...

They are available on the market but all the samples I bought are not good.

Gianrico,

Understood. Let me have a look at these when they get in and we can hopefully find the root cause and get you squared away. I will leave this thread up to continue this once the samples get here. 

Ok, if you need the DHL tracking n°, ask me. For now I'll use the A2 on my boards.

Thanks Gianrico!

Hi Carolus, some news? Are the parts arrived?

Ciao

Hey Gianrico,

I did receive the parts on Friday, and I have confirmed your issue on my bench here. These are in fact trimmed incorrectly to A2 rather than A3. I am working with the other teams here to better understand what has happened and to get this corrected. Thank you so much for bringing this to our attention!

Hi Carolus, you're welcome!

Thank you for the report. For now I'm temporary using the A2 with firmware corrections.

You can close the thread if you want but I'd love to keep getting updates.

Ciao

GIanrico