ADA4927 Power Down Pin

Document created by analog-archivist Employee on Feb 23, 2016
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The data sheet spec for the powerdown pin quotes voltages e.g. 3.2V as if
relative to a ground pin. However there is no ground pin. Some of the graphs
quote supplies of +/-2.5V so 3.2v would not seem to be a good idea. Is the
device actually controlled by the voltage relative to the +Vs or to the -Vs
pins?

 

The levels in the spec tables can be referred to the positive supply.  So, for
the “Enabled” case of >3.2V, it would mean “greater than 1.8V down from the
positive supply – the same approach can be used for the “Powered Down” case of
<1.8V, where it would mean “less than 3.2V below the positive supply.  A
similar situation often occurs with output swing levels and input common-mode
range, which are sometimes specified in absolute volts, and sometimes relative
to the supplies.  The numbers are nonetheless correct, since “ground” on +/-5V
supplies, where the specifications are defined, is zero volts, and there is
generally a ground plane defining zero volts between the two supplies.

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