Do I need separate Op-Amp for REFIO if Driving multiple AD7380 using LTC6655

Question

Hi, I need to use 3 to 4 AD7380 for data collection and using 1 LTC6655 for Reference Voltage. I do not know whether the sink current of REFIO pin is suffice. Do I need 3 to 4 Op Amp for buffering each AD7380 REFIO pin if I need to achieve a high ENOB?

mashimaro · Accepted Answer

AD7380的Vref input current在使用external reference的情况下，最大值为0.51mA. 如果是4个AD7380, 一共需要2mA左右。LTC6655的负载调整率是 50ppm/mA。那么2mA的电流会带来100ppm的波动，可能会对ADC的采样造成影响，建议加1个buffer。 
 可以考虑AD7380的datasheet里推荐的buffer, 比如说ADA4807)

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Do I need separate Op-Amp for REFIO if Driving multiple AD7380 using LTC6655