Is it possible to use AD7680 by External clock 4MHz?
When using external clock , what is minimum clock frequency?
I am not sure what you mean about AD7680 by external clock frequency. Can you expound further about it. But with regards AD7864, please take note on Table 2 of the AD7864 datasheet, conversion (Tconv) requires 13 clock cycles. So in the case of using external clock of 5Mhz, Tconv = 2.6us. Lowering the external clock frequency will result to slower conversion time. This means that the minimum external clock frequency would depend on how much conversion time you allowed on your application.
Fext = (13/Tconv)
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