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Tool/software:
Hi team.
my customer is developing a precision 16bit data acquisition system with using a SAR adc without refence buffer, can you help me on how to select a proper ref buffer for the ADC ?
and what is the key concerns of this selection?
Hi Eric,
can you help me on how to select a proper ref buffer for the ADC ?
If the customer is using bandgap reference, I would suggest to follow the table below. REF35, REF34 are reasonable cost. Depending on your accuracy requirements over temperature, REF35 or equivalent may be required.
https://www.ti.com/lit/an/snaa320b/snaa320b.pdf?ts=1730160306059
what is the key concerns of this selection?
For op amp, such as OPA2188-Q1 or similar to use as reference voltage, the concerns are about driving capacitive load (reference stability), accuracy and temperature drift over time.
The following technique applies to OPA350 as voltage reference with large capacitive load. If you want to use OPA2188-Q1 to drive a reference voltage, you have to tell me how much capacitive load, and the op amp has to be compensated in order to drive it. (op amp can not drive large capacitive load directly without oscillation concerns).
OPA350 as Reference 10292024.TSC
If you have other questions, please let me know.
Best,
Raymond
Hi Raymond，
why the VREF noise must be at least 5 times smaller than the ADC noise？
we can do a math calculation：sqrt（1+5*5 ）=5.099 ，so the vref noise take the propotion as 1/5.1=0.19 ,it is too big for the total noise
Hi Eric,
Here is open loop AC analysis for OPA350.
OPA350 capacitive load AC Anslysis 10302024.TSC
we can do a math calculation：sqrt（1+5*5 ）=5.099 ，so the vref noise take the propotion as 1/5.1=0.19 ,it is too big for the total noise
Regarding to the noise issue relating to ADC, please submit a query for the the ADC team. The HVA team is supporting op amp related application issues.
Best,
Raymond
