NEC NEC PD78081(A), User Manual

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CHAPTER 10 A/D CONVERTER
10.5 A/D Converter Cautions
(1) Power consumption in standby mode
The A/D converter operates on the main system clock. Therefore, its operation stops in STOP mode. As a
current still flows in the AV
REF
pin at this time, this current must be cut in order to minimize the overall system
power dissipation. In Figure 10-9, the power dissipation can be reduced by outputting a low-level signal to
the output port in standby mode. However, there is no precision to the actual AV
REF
voltage, and therefore
the conversion values themselves lack precision and can only be used for relative comparison.
Figure 10-9. Example of Method of Reducing Current Dissipation in Standby Mode
(2) Input range of ANI0 to ANI7
The input voltages of ANI0 to ANI7 should be within the specification range. In particular, if a voltage above
AV
REF
or below AV
SS
is input (even if within the absolute maximum rating range), the conversion value for that
channel will be indeterminate. The conversion values of the other channels may also be affected.
Series Resistor String
V
DD
AV
REF
AV
REF
= V
DD
AV
SS
Output Port
.
.
µ
PD78082