ADS8863_14 Datasheet, PDF (29/49 Pages) Texas Instruments – 16-Bit, 680-kSPS, Serial Interface, microPower, Miniature, True-Differential Input, SAR Analog-to-Digital Converter

ADS8863
www.ti.com
SBAS571A – MAY 2013 – REVISED DECEMBER 2013
POWER SAVING
The device has an auto power-down feature that powers down the internal circuitry at the end of every
conversion. Referring to Figure 65, the input signal is acquired on the sampling capacitors when the device is in
a power-down state (t_acq); at the same time, the result for the previous conversion is available for reading. The
device powers up on the start of the next conversion. During conversion phase (t_conv), the device also consumes
current from the reference source (connected to pin REF).
Device Phase
tTHROUGHPUT
tCONV
tACQ
tCONV
2 * tTHROUGHPUT
tACQ
IAVDD
~50000X
~50000X
IREF
~1200X
~1200X
IAVG(AVDD+REF)
~2X
Figure 65. Power Scaling with Throughput
The conversion time, t_conv, is independent of the SCLK frequency. When operating the device at speeds lower
than the maximum rated throughput, the conversion time, t_conv, does not change; the device spends more time in
power-down state. Therefore, as shown in Figure 66, the device power consumption from the AVDD supply and
the external reference source is directly proportional to the speed of operation. Extremely low AVDD power-down
current (50 nA, typical) and extremely low external reference leakage current (250 nA, typical), make this device
ideal for very low throughput applications (such as pulsed measurements).
2
1.6
1.2
0.8
0.4
0
0 85 170 255 340 425 510 595 680
Throughput (kSPS)
C00
Figure 66. Power Scaling with Throughput
Copyright © 2013, Texas Instruments Incorporated
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