ADS131M02-Q1: fDATA something is wrong

Hello Kaixin,

welcome to our e2e forum and thank you for your interest in our ADS131M02-Q1.

Do you have a scope plot showing the timing of the DRDYn signal? The time between the DRDYn falling edges will indicate the conversion time.
Did you read back the OSR[2:0] bits to confirm they are properly set?

Regards,
Joachim Wuerker

1.This is the schematic.

2.Register is the default value，enable CRC.

OSR[2:0] bits is111, the CLKIN is 8.192MHZ, and the PWR is 10b,gain is 128,but data rate is 4kSPS.

3.DRDYn  signal is:

Hello Kaixin,

that is weird. The schematic looks okay to me.

Could you try sending the STANDBY command before you change the OSR[2:0] registers? And then send the WAKEUP command afterwards?
Please read back the OSR[2:0] registers to make sure they have changed correctly.

BTW: It seems like you are working on a BMS. You might also consider ADS131B02-Q1 in case you need better offset performance for the current shunt measurement. The ADS131B02-Q1 would also integrate an oscillator so that an external clock would not be required anymore.

Regards,
Joachim Wuerker

Hello Kaixin,

I got confirmation from our design team that special register settings should only be changed while the device is in standby mode.
The following registers should only be written in standby mode:

• CLOCK
• CFG
• THRSHLD_MSB
• THRSHLD_LSB
• CHx_CFG

We will have to add this information to the next datasheet revision.
Please let me know if this resolves the issue for you.

Regards,
Joachim Wuerker

I sending the STANDBY command before you change the OSR[2:0] registers, but  data rate always is 4kSPS.

Hi Kaixin,

that is really odd. Would you mind sending me scope shots of the SPI communication with the device (Signals: CSn, SCLK, DIN, DOUT, DRDYn) for sending the STANDBY command, the WREG command to change the OSR, the RREG command to read back the OSR bits, and the WAKEUP command?

Regards,
Joachim Wuerker

Sorry，there is no oscilloscope now, can I contact you when there is an oscilloscope behind

Certainly Kaixin.

A logic analyzer image should work as well though.

Regards,
Joachim Wuerker

Sorry, my logic analyzer can't read sclk image, relatively cheap.

Alright. I will wait for your oscilloscope images then.
You could also use a slower SCLK frequency if that would help taking images with your logic analyzer.

Did you confirm by reading back the OSR[2:0] bits that the OSR was always set correctly?

Regards,
Joachim Wuerker

Yes，I  reading back the OSR[2:0] bits .The OSR was always set correctly. The CLKIN is 8.192MHZ, Can I use MCU sclk?

Not sure I understand your question.
The CLKIN is used to drive the ADC clock, while the SCLK is purely used for the SPI. You can use a different SCLK frequency compared to the CLKIN frequency.

Regards,
Joachim Wuerker

• It means whether I can use sclk as clkin

In principle yes.
You need to make sure your SCLK frequency meets the requirements stated in the Recommended Operating Conditions table.
CLKIN would require a continuously running clock, while you might not keep SCLK running when you are not communicating with the device. However as long as you meet all timing requirements (especially the relationship between SCLK and CSn), then you could keep SCLK running even when not communicating (that is, when CSn is high).

Regards,
Joachim Wuerker

ok，thanks

I used an external crystal oscillator, just asking if sclk can be used as clkin.

Thanks

Yes, but you need to watch out for the restrictions I mentioned above.

Regards,
Joachim Wuerker

• Thank you. I'll call you when I have an oscilloscope

Did you manage to resolve the issue on the meantime?

Regards,
Joachim Wuerker

• It's not solved. I don't know what to do, so we stop

Hi Kaixin,

I am sorry to hear that.

Did you manage to take any oscilloscope shots of the communication? That is usually the first and most important thing to do to debug any communication issues with our ADCs. So far we have always managed to get the ADC working in a customer application.

Also did you try a different unit just to make sure the unit you are using did not get damaged in any way?

What ADC solution did you evaluate then instead?
Our ADS131M0x-Q1 and ADS131B0x-Q1 are successfully used by many of our customers in BMS.
I don't want you to walk away with a bad feeling about our ADCs.

Regards,
Joachim Wuerker

• We will continue to use the board. We will adjust it later