What maximum current is required on the AD7714 reference input (REF IN+)? REF IN+ will be at 3.0V. REF IN- will be at GND. AVDD and DVDD will be at 3.4V. I don't see this figure on the datasheet.
Thank you ferdi. That's not much.
For AVDD = +3 to +3.6, VREF should be +1.25 V. Therefore, if REFIN(-) is at GND then REFIN(+) should be +1.25 V since VREF = REF(+) - REF(-). But you stated REFIN(+)=3 V, can you check this?
We'll get back to you about the maximum current on the REFIN inputs.
We are using one of the Y parts, so it looks like the maximum VREF is 1.75V. Is that how you see it? We were planning to use a 3V reference, so looks like this is not going to work. I'm glad I asked the question. Had not noticed this before.
One of my colleagues says that he consulted with Analog Devices and they said that it was ok to use a 3V reference with a supply voltage of 3.4V. Does that sound possible?
If you're looking to its absolute maximum ratings, yes, you can use 3 V for REFIN with a supply voltage of 3.4 V. My concern here is the accuracy of your system since VREF goes higher than what is the normal value. I have tried the Temperature Demo of AD7714 Eval Board and it reads more than 80 deg Celsius using REFIN+ = 3 V with an AVDD = 3.3 V. The normal temperature reading should be 21 deg Celsius with REFIN+ = 1.25 V for our setup in this case.
By the way, REFIN inputs have passed +/-100 mA current stress test which means that the device can still work properly with this amount of source/sink current. But at 260 mA, the device may behave strangely as it has reached its limit.
Please don't hesitate to ask if you require anything else.
Thanks for the info on the reference. We are designing a power supply for the 3V reference, which will supply several ICs, and need to know the current that can typically be expected into REFIN+. It's not going to be 100 or 260 mA is it?
I have checked the AD7714 evaluation board. Voltage is applied on the REFIN+ pin and current is measured. Typical current is 0.36 uA to 1 uA for REFIN+ voltage of 1.23 V to 3.3 V with roughly 0.03 uA increase for every 0.1 voltage step. The values were consistent for the 2 devices tested.
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