Datasheet

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SBAS314B − APRIL 2004 − REVISED JANUARY 2009
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16
SYMBOL DESCRIPTION MIN MAX UNITS
t
9
(1)
SCLK high after DRDY/DOUT goes low to activate Standby mode 0 8.272 ms
t
10
(1)
Standby mode activation time 8.272 8.304 ms
t
11
(1)
Data ready after exiting Standby mode 27.7 28.1 ms
(2)
Values given for f
CLK
= 2MHz. For different f
CLK
frequencies, scale proportional to CLK period.
DRDY/DOUT 23 22 21
124
023
SCLK
Standby Mode
Start Conversion
Data Ready
t
9
t
10
t
11
Figure 28. Standby Mode Timing (can be used for single conversions)
SYMBOL DESCRIPTION MIN MAX UNITS
t
12
(1)
Data ready after exiting Standby mode and calibration 78.8 79.7 ms
(1)
Values given for f
CLK
= 2MHz. For different f
CLK
frequencies, scale proportional to CLK period.
Standby Mode
Begin Calibration
Data Ready After Calibration
t
10
t
12
DRDY/DOUT 23
12425
22 21 0 23
SCLK
Figure 29. Standby Mode with Self-Calibration Timing (can be used for single conversions)
SINGLE CONVERSIONS
When only single conversions are needed, Standby
mode can be used to start and stop the ADS1222. To
make a single conversion, first enter the Standby mode
holding SCLK high. Now, when ready to start the
conversion, take SCLK low. The ADS1222 wakes up
and begins the conversion. Wait for DRDY/DOUT to go
low, and then retrieve the data. Afterwards, take SCLK
high to stop the ADS1222 from converting and re-enter
Standby mode. Continue to hold SCLK high until ready
to start the next conversion. Operating in this fashion
greatly reduces power consumption since the
ADS1222 is shut down while idle between conversions.
Self-calibrations can be performed prior to the start of
the single conversions by using the waveform shown in
Figure 29.