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ADS1262: ADS1262EVM

nikhil chauhan
Intellectual 425 points
Part Number: ADS1262

Hi,

I am working on  ADS1262 EVM and I am using it for the first time.

I am trying to read the voltage applied at one of the analog input channel through a calliberator. I have connected +ve terminal to the IN3 on the ADS1262EVM and COM to the IN4 and when I tried to capture it by ADC-PRO I got the below error:

ADC1 low reference fault, PGA negative rail fault,PGA positive rail fault, ADC1 input out of range fault.

I tried it even with PGA- BYPASS but still got the same error.

Can you please tell me how to proceed with it if the above method is not correct?

Thanks and regards,

Nikhil

  • 0
    TI__Mastermind 44680 points
    Hi Nikhil,

    Would you be able to share your ADS1262 register settings?


    For the "ADC1 low reference fault":
    What are you using for the reference source? If using an external reference, what is the external reference voltage? Maybe the reference mux settings are incorrect or perhaps the reference source is not correctly biased with respect to the AVSS voltage on the ADS1262EVM. If using the internal reference, then I would double check the register settings to make sure it is enabled and that the REFOUT pin is not to heavily loaded.

    For the other faults:
    Do you know what the COM voltage of the calibrator is with respect to the ADS1262EVM's ground? Is COM connected to any of the GND, AVSS, or REFOUT nets on the EVM? Also, what is the voltage on +ve and what is the configured PGA gain? It sounds like you might have a combination of issues here. Maybe the calibrator's voltage is not correctly biased to the ADC's common-mode input range, and perhaps the input voltage is being gained up above the reference voltage, causing the ADC's output code to clip to full-scale.

    Please note that the PGA alarms will still be triggered when the PGA is bypassed. Generally, you can ignore these alarms when you bypass the PGA; however, the low reference and input out-of-range flags are still indicative of a problem (even with the PGA bypassed).

    Best regards,
    Chris
  • 0 in reply to Christopher Hall
    Intellectual 425 points

    Hi Christopher,

    Thanks for your reply.

    Well, I am using internal reference and I have enabled the BYPASS and disabled CHOP. I am feeding 500mV from calibrator.

    The COM is connected to AIN4 of EVM and +ve to AIN3.  AIN3 voltage with respect to EVM GND is same as AIN3 with respect to AIN4 i.e. 500mV.

    This is  register map 

    Fullscreen 6242.ADS126x Register Map.txt Download 
    Name	Addr	R/W	Init	Value
ID	0x00	R	-	0x03
POWER	0x01	R/W	0x11	0x11
INTERFACE	0x02	R/W	0x05	0x05
MODE0	0x03	R/W	0x00*	0x10
MODE1	0x04	R/W	0x80*	0x00
MODE2	0x05	R/W	0x04*	0x08
INPMUX	0x06	R/W	0x01	0x34
OFCAL0	0x07	R/W	0x00	0x00
OFCAL1	0x08	R/W	0x00	0x00
OFCAL2	0x09	R/W	0x00	0x00
FSCAL0	0x0A	R/W	0x00	0x00
FSCAL1	0x0B	R/W	0x00	0x00
FSCAL2	0x0C	R/W	0x40	0x40
IDACMUX	0x0D	R/W	0xBB	0xBB
IDACMAG	0x0E	R/W	0x00	0x00
REFMUX	0x0F	R/W	0x00	0x00
TDACP	0x10	R/W	0x00	0x00
TDACN	0x11	R/W	0x00	0x00
GPIOCON	0x12	R/W	0x00	0x00
GPIODIR	0x13	R/W	0x00	0x00
GPIODAT	0x14	**	0x00	0x00

    Under 2V it is giving the same error but as I feed voltage more than 2V  through calibrator with +ve connected to AIN3 and COM connected to AIN4,then it gives this error.

    Please guide me.

    Thanks and regards,

    Nikhil

  • 0 in reply to nikhil chauhan
    TI__Mastermind 44680 points
    Hi Nikhil,

    When bypassing the PGA (BYPASS = 1), you can ignore the "PGARAIL_N". This flag will always be set when the negative input voltage is less than 0.3V. Regardless, if you want to try to resolve this error flag, then perhaps you could connect the COM pin of your calibrator (assuming it is a high input impedance) to AINCOM on the ADS1262 and enable the VBIAS level shifter to set the common mode voltage to ~2.5V.

    The"INPRNG" flag is a different error that should not be ignored. Typically, you will see this error when the input voltage (times the input gain) exceeds VREF. With the internal reference enabled and PGA bypassed you shouldn't see this error flag until the input signal is >= 2.5V.

    To check acceptable input signal ranges, please refer to the "PGA1 Input Range" tab in this Excel calculator: www.ti.com/.../ads126x-calc-tool

    Let me know if this helps,
    Chris