ad7883br Analog Devices, Inc., ad7883br Datasheet - Page 10

• Manufacturer Part Number: ad7883br
• Description: Lc2mos 12-bit, 3.3 V Sampling Adc
• Manufacturer: Analog Devices, Inc.

AD7883
POWER-DOWN CONTROL (MODE INPUT)
The AD7883 is designed for systems which need to have mini-
mum power consumption. This includes such applications as
hand held, portable battery powered systems and remote moni-
toring systems. As well as consuming minimum power under
normal operating conditions, typically 8 mW, the AD7883 can
be put into a power-down or sleep mode when not required to
convert signals. When in this power-down mode, the AD7883
consumes 1 mW of power.
The AD7883 is powered down by bringing the MODE input
pin to a Logic Low in conjunction with keeping the RD input
control High. The AD7883 will remain in the power-down
mode until MODE is brought to a Logic High again. The
MODE input should be driven with CD4000 or HCMOS logic
levels.
It is recommended that one “dummy” conversion be imple-
mented before reading conversion data from the AD7883 after it
has been in the powerdown mode. This is required to reset all
internal logic and control circuitry. Allow one clock cycle before
doing the dummy conversion. In a remote monitoring system
where, say, 10 conversions are required to be taken with a sam-
pling interval of 1 second, an additional 11th conversion must
–10–
be carried out. Figure 14 gives a plot of power consumption as a
function of time for such operation. The total conversion time
for each cycle is 11 20 s (where 20 s is the time taken for a
single conversion) corresponding to 2.2 10
Figure 14. Power Consumption for Normal Operation and
Power-Down Operation vs. Time
Hence:
Average Power
CONSUMPTION
POWER
– mW
8
1
0
CONVERTING
2.2 x 10
= Power
= {8 mW
+ {1 mW
= 1.0015 mW
–4
POWER-DOWN
CONVERTING
(2.2
(0.9998)}
TIME – secs
CONVERTING
1
10
+ Power
–4
)}
–4
POWER-DOWN
secs.
POWER-DOWN
REV. 0
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