Datasheet

AD7466/AD7467/AD7468
Rev. C | Page 20 of 28
POWER CONSUMPTION
The AD7466/AD7467/AD7468 automatically enter power-
down mode at the end of each conversion or if
CS
is brought
high before the conversion is finished.
When the AD7466/AD7467/AD7468 are in power-down mode,
all the analog circuitry is powered down and the current con-
sumption is typically 8 nA.
To achieve the lowest power dissipation, there are some
considerations the user should keep in mind.
The conversion time is determined by the serial clock
frequency; the faster the SCLK frequency, the shorter the
conversion time. This implies that as the frequency increases,
the part dissipates power for a shorter period of time when the
conversion is taking place, and it remains in power-down mode
for a longer percentage of the cycle time or throughput rate.
Figure 26 shows two AD7466s running with two different
SCLK frequencies, SCLK A and SCLK B, with SCLK A having
the higher SCLK frequency. For the same throughput rate, the
AD7466 using SCLK A has a shorter conversion time than the
AD7466 using SCLK B, and it remains in power-down mode
longer. The current consumption in power-down mode is very
low; thus, the average power consumption is greatly reduced.
This reduced power consumption can be seen in
Figure 25,
which shows the supply current vs. SCLK frequency for various
supply voltages at a throughput rate of 100 kSPS. For a fixed
throughput rate, the supply current (average current) drops as
the SCLK frequency increases because the part is in power-
down mode most of the time. It can also be seen that, for a
lower supply voltage, the supply current drops accordingly.
390
SUPPLY CURRENT (μA)
360
330
300
270
240
210
180
150
120
90
60
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
SCLK FREQUENCY (MHz)
f
SAMPLE
= 100kSPS
TEMP = 25°C
V
DD
= 3.6V
V
DD
= 3.0V
V
DD
= 2.2V
V
DD
= 2.7V
V
DD
= 1.8V
V
DD
= 1.6V
02643-026
Figure 25. Supply Current vs. SCLK Frequency
for a Fixed Throughput Rate and Different Supply Voltages
SCLK B
SCLK A
116
116
CONVERSION TIME A
CONVERSION TIME B
1/THROUGHPUT
CS
02643-027
Figure 26. Conversion Time Comparison for Different SCLK Frequencies and a Fixed Throughput Rate
POWER DOWN TIME B
1/THROUGHPUT B
1/THROUGHPUT A
POWER DOWN TIME A
CONVERSION TIME A
CONVERSION TIME B
CS A
S
CLK
CS B
116
02643-028
Figure 27. Conversion Time vs. Power-Down Time for a Fixed SCLK Frequency and Different Throughput Rates