Datasheet

AD5590
Rev. A | Page 41 of 44
ADC Power vs. Throughput Rate
By operating the ADC in autoshutdown or autostandby mode,
the average power consumption of the ADC decreases at lower
throughput rates. Figure 73 shows how, as the throughput rate is
reduced, the ADC remains in its shutdown state longer and the
average power consumption over time drops accordingly.
For example, if the ADC is operated in a continuous sampling
mode with a throughput rate of 100 kSPS and an ASCLK of
20 MHz, with PM1 = 0 and PM0 = 1 (that is, the device is in
autoshutdown mode), the power consumption is calculated
as follows: the maximum power dissipation during normal
operation is 12.5 mW. If the power-up time from autoshutdown
is one dummy cycle, that is, 1 µs, and the remaining conversion
time is another cycle, that is, 1 µs, the ADC dissipates 12.5 mW
for 2 µs during each conversion cycle. For the remainder of the
conversion cycle, 8 µs, the ADC remains in shutdown mode. The
ADC dissipates 2.5 µW for the remaining 8 µs of the conversion
cycle. If the throughput rate is 100 kSPS, the cycle time is 10 µs
and the average power dissipated during each cycle is
mW502.2μW5.2
10
8
mW5.12
10
2
=×+×
When operating the ADC in autostandby mode, PM1 = PM0 = 0
at 5 V, 100 kSPS, the ADC power dissipation is calculated as
follows: the maximum power dissipation is 12.5 mW at 5 V during
normal operation. The power-up time from autostandby is one
dummy cycle, 1 µs, and the remaining conversion time is another
dummy cycle, 1 µs. The ADC dissipates 12.5 mW for 2 µs during
each conversion cycle. For the remainder of the conversion cycle,
8 µs, the ADC remains in standby mode dissipating 460 µW for
8 µs. If the throughput rate is 100 kSPS, the cycle time is 10 µs
and the average power dissipated during each conversion cycle is
mW868.2μW
10
8
mW5.12
10
2
=×+×
Figure 73 shows the power vs. throughput rate when using the
autoshutdown mode and autostandby mode with 5 V supplies.
At the lower throughput rates, power consumption for the
autoshutdown mode is lower than that for the autostandby
mode, with the ADC dissipating less power when in shutdown
compared to standby. However, as the throughput rate is
increased, the ADC spends less time in power-down states;
thus, the difference in power dissipated is negligible between
modes.
10
0.01
0.1
1
0 50 100 150 200 250 300 350
THROUGHPUT (kSPS)
POWER (mV)
ADCV
DD
= 5V
AUTOSTANDBY
AUTOSHUTDOWN
07691-073
Figure 73. Power vs. Throughput Rate in Autoshutdown
and Autostandby Mode