AD9240: Maximum allowed power supply ripple

Q

What's the maximum ripple voltage for Analog Supply (+5V, AVDD).
AD9240 is used in differential mode.

A

The spec allows a tolerance of +/-5% on the supply but this only refers to DC.
The AD9240 is a high speed 10Msps ADC and as such the supplies need to be well
regulated and decoupled. Any AC spurious ripple which enters through the power
supply has the possibility of modulating the input signal and showing up at the
output as a spurious tone.

Most high speed ADC offer almost no power supply rejection of frequencies above
a few hundred Hertz. Solid power supply regulation and filtering in addition to
local power supply decoupling at the IC power pins are essential to the correct
operation of such high speed ADCs.

The short answer to your question is don’t take short cuts when designing your
power supply for the AD9240.
I have enclosed the final chapter of our most recent seminar which deals
specifically with physical board design.

please also note for new designs requiring >10Msps 14bit high speed ADC, I
would recommend the . AD9240 still has a long expected lifetime, AD6644 is the
more modern product.

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