AD7779 No-OS Driver with ESP32 – AINM_UV and ERR_REF_DET Errors

Hi, SRAVANKUMARVEESAM .

I will contact the product owner and get back to you.

Regards,
Jo

Hi SRAVANKUMARVEESAM ,

For single-ended inputs, please refer to Figure 89.

The absolute analog inputs must not exceed AVSS +0.1 to AVDD-0.1, or 0.1 to 3.2 V in your case.

The AINM in this case, cannot be connected to AGND. Please ensure both the AINP and AINM are within 0.1 to 3.2V.

Thanks,
Janine

Hi SRAVANKUMARVEESAM ,

Please refer to this document for more details on the analog input limitations

(+) AD777x:What is the input voltage range of the ADC? - Documents - Precision ADCs - EngineerZone

Thanks,
Janine

HI Janine, Thanks for the response. Can you please clarify below 

1. In my case can i tie all AINM inputs to VCM (single ended Inputs)?

2. ADC values for single ended input when connected as 1 for 1.65 to 2.5V will be 0x000000 to 0x7FFFFF and for 0.1 to 1.65v will be 0X800000 to 0xFFFFFF?

Hi SRAVANKUMARVEESAM ,

1. Yes. You can tie all AINM inputs to VCM. The optimal VCM to maximize the range would be Vref/2 if the other pin (AINP) swings from 0.1 to 3.2. What is your Vref in this case?

2. The conversion output will still be the differential input AINP - AINM. Is the AINP input from 1.65 to 2.5?

Thanks,
Janine

1. My vref is currently 2.5V and im currently getting VCM output as 1.65V. So can i connected a 1.25V ref derived from my 2.5V using resistor divider network and connect them to All AINMs for better utlisation of range?

2. My AINP will swing from 0.15 to 3V.

Cant find the answer here

Hi SRAVANKUMARVEESAM ,

1. The VCM is set to (AVDD1+AVSS)/2. Yes you can connect the 1.25V to maximize the input range.

2. The output code of the ADC will be the differential input AINP - AINM. Please refer to the snapshot below from the datasheet.

Thanks,
Janine

Hi SRAVANKUMARVEESAM ,

The input pins are limited by the supplies, AVDD, AVDD and REF.

If AVDD = 3.3V, AVSS = 0V, REF = 2.5V

The absolute voltage is limited by AVSS+0.1 to AVDD-0.1 (0.1 to 3.2)

The differential voltage is limited to +-Vref (AINP - AINM within +-2.5)

If AINM is connected to 2.5, then AINP is limited to 0.1 to 3.2.

Thanks,
Janine

Thanks for the clarification Janine. We are clear now for our development