AD7678: Driver

Document created by analog-archivist Employee on Feb 23, 2016
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data sheet for AD7678 says that its input driver must settle fast and be short
circuit limited if its using different rails to the single rail ADC.
It recommends the AD8021 for its performance. - But its by no means short
circuit protected!
- Can you recommend a suitable high performance driver that IS suitably
protected?

 

The AD7678 specifies an input buffer with a short-circuit current limitation.
Looking at the AD8021 datasheet, the output is limited to 75mA when used on
+/-5V supply (the maximum required for the AD7678) and the power dissipation is
within the limits of the device over the entire temperature range. It is only
on supplies of +/-12V where the maximum output current could begin to cause a
problem for the ADC inut protection diodes and where the power dissipation of
the device could cause the die temperature to exceed its maximum ratings.

The AD8021 offers excellent performance for the device and its interaction with
the AD7678 input protection diodes is suitable for most realistic applications.

The AD8139 was not released when the AD7678 was released, but it would be a
suitable differential driver for the ADC.

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