Category: Hardware
Product Number: AD7124-8
Hi Team,
I am testing AD7124-8 on EVAL-AD7124-8ASDZ and seeing an excitation current mismatch.
Setup:
- EVK: EVAL-AD7124-8ASDZ
- External connection: CN0383, Figure 21 (multiple 3-wire RTD, low-side RREF topology)
- RTD replaced with fixed 100 ohm resistor
- RREF = 4.7 kohm
- Reference source = external REFIN1
Current firmware configuration:
- Excitation current configured = 100 uA per IDAC
- PGA gain = 8
- Unipolar mode
- Input/reference buffers enabled
Register configuration:
- CONFIG0 (0x19): 0x01E3
- bipolar=0, REF_BUFP=1, REF_BUFM=1, AIN_BUFP=1, AIN_BUFM=1, REF_SEL=REFIN1, PGA=8
- FILTER0 (0x21): 0x000060
- ADC_CONTROL (0x01): 0x0000 (continuous mode defaults, internal REF_EN disabled)
- ERROR_EN (0x07): 0x000800 (REF_DET_ERR_EN)
Channel assignments in code:
- CHANNEL_0 (0x09) = 0x8043 (AIN2/AIN3)
IDAC routing table in code:
RTD1: IDAC1->AIN0, IDAC2->AIN1.
When configured for 100 uA, measured current is about 160 uA. I measured current by inserting ammeter in series between IOUT0 node (AIN0) and RTD lead to measure source branch current.
Are there EVK jumper/switch settings that can cause this behavior?
