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ADS125H01: ADS125H01

Part Number: ADS125H01

ADS125H01 Main Status (STATUS0) Register (address = 01h) [reset = 01h],shows that there is a Reference Voltage Alarm (bit three of this register),This bit sets when the reference voltage falls below < 0.4 V (typical). The alarm updates at each new conversion cycle (autoreset). However, the voltage reference is selected as 2.5V and the oscilloscope shows that the voltage of pin1 is actually 2.5V and Pin 32 is well grounded.

The dataRegisters is read from RREG Command.

  • The ADC reference chip is chosen as ADR4525ARZ, Ultralow Noise, High Accuracy 5V to 2.5V Voltage References.

  • Hi Ziheng,

    Which reference setting do you have selected in the REF register? It is possible that the other set of external reference inputs are selected.

    Can you also share a schematic of your system?

    -Bryan

  • No matter how I set the reference register (05H or 0AH), the STATUS0 Register is always 05H. The schematic of the ADC is depicted as follows. ADR4525ARZ is the REF chip with 2.5V output.

  • Hi Ziheng,

    Do you have a logic analyzer? Can you probe SCLK, CS1, CS2, DOUT, and DIN during the RREG command so we can see what is being sent to the ADC and what the ADC is sending back? I will be honest I do not see how the screenshot you sent of dataRegisters has anything to do with reading back the STATUS0 byte.

    You can also try applying an input to the ADC and seeing what the output code is to see if the ADC is recognizing the VREF voltage correctly. Try a 1V input with G = 1 and see what the output code is. And please just provide the output code in hex, do not try to parse or manipulate the output code in any way.

    -Bryan

  • Hi Ziheng,

    I also noticed that your system has separate ground net names (AGND and DGND). This commonly means that there are separate or split ground planes, which we do not recommend. Best practice would be to have a solid ground plane for both analog and digital ground, assuming this is not already the case for your system

    -Bryan

  • The dataRegisters stored the values of all registers.STATUS0 is the second member of the dataRegisters array.

    I tried 0V,1V, and up to 2.5V when the gain is selected from 0.125 to 1. However, no matter how the input voltage of the ADC is changed, the output code of the ADC is always FF 12 00 AA FF FF FF 24 or FF 12 00 AA 00 00 00 2B.

  • It is a four-layer PCB and the ground board is separated into the analog ground plane and the digital ground plane (AGND and DGND). AGND and DGND are connected with a 0-ohm resistor.

  • Hi Ziheng,

    Do you have a logic analyzer? As I said in my last post, we need to look at the communication between the ADC and MCU to better understand what is happening here. There could be a timing issue, or a command might not be getting issued correctly.

    -Bryan