Hi to all,
my acquisition and processing board has 12 AD7626 channels interfaced with a FPGA.
I have to provide a voltage reference source for all ADCs in simultaneous acquisition mode at 10MSPS.
So, following the application note "Voltage Reference Design for Precision Successive-Approximation ADCs" by Alan Walsh,
I choose the topology using a unit gain op-amp amplifier for each ADC (each op-amp fed from a unique ADR4540 voltage reference): see the topology below suggested in the AD7626 datasheet.
Supposing a AD7626 Vref input current value of 3.3mA average (10 times the AD7980; 1MSPS Pulsar ADC), I should
select a op-amp with internal output impedance low as 0.01 Ohm at 10MHz: this value is too low even for hi-speed op-amp like ADA4841.
So my question is regarding the AD7626 Ref input current value: is my hypothesis correct (Iref = 10 * Irref_AD7980)?
May be the AD7626 has a different internal topology and, for this reason, the Iref value is negligible and is not provided?
Thank you for any help.