LM36011EVM: Can't Read LM36011 I2C data

Hi Steven,

What interface is your customer using for I2C communication?

Please make sure that VIO is pulled high and Ground is also connected to I2C interface in addition to SCL & SDA lines.

Best,
-Harini

LM36011.docxDear Sir,

I saw I2C ACK not correct, please help again.

(see attached file)

Thanks!

Steven

Hi Harini,

I am the FAE supporting this issue with Steven.

As Steven pointed out, the ACK waveform was pretty weird (a step-like waveform), and any I2C operation after that was not correct.

Would you be able to do some tests on the LM36011 EVM and send us the waveform?

For example, you might want to try reading register 0x01 and show us the waveform like the one in the Word file Steven sent you.

Thank you!

Best regards,
Roy Hsu

Hi Roy, Steven,

Sure, I'll get I2C read/write scope captures today.

Best,
-Harini

Hi Roy, Steven,

Below is the SCL & SDA waveform on my setup. As you can see, the LM36011 pulls down the SDA line during the 9th clock pulse, signifying an acknowledge.

What is the pull-up resistor value is the customer using? A pullup resistor between the VIO line of the controller and SDA must be greater than [(VIO – VOL) / 3 mA] to meet the VOL requirement on SDA. VOL max is 400mV. So, Pullup of > 1kohm need to be used. 

Best,

-Harini

Hi Harini,

Thanks for the effort. I've passed your result to the customer already.

Actually two 1-kohm resistors are used in the LM36011 EVM, according to your suggestion, these should be changed to the ones greater than 1 kohm, am I right?

Besides, the customer saw the weird waveform when SCL frequency was about 140 kHz.

Would you be able to see if the operation is still normal under a <400 kHz SCL?

Thank you!

Best regards,

Roy Hsu

Hi Roy,

Pull-up resistor need to be >= [(VIO – VOL) / 3 mA] > 966ohm. 1kohm should be fine. In fact we did complete evaluation with 1 kohm and didn't run into any I2C communication issue. 

Also, please make sure the customer is using 3.3V for VIO. 

Btw, are they using our EVM (or) do they have a custom board with LM36011?

Here is the scope shot with 100kHz SCL.

Best,

-Harini