Datasheet

C nverto
Selected
Channel
SelectedChan eln
(1)
Sleep
Sleep
Satust
Busy
(2)
P RCONW
(3)
Input Multip exerl
t
ACQ
t
CONV
t
SLEEP
t
ACQ
t
ACQ
t
CONV
t
CONV
t
SLEEP
C nverto
Selected
Channel
C nverto
Selected
Channel
Acquire
Selected
Channel
Acquire
Selected
Channel
Acquire
Selected
Channel
t
PU
Awake
t
PU
Awake
t
PU
Awake
t
CYCLE
(4)
ADS7924
www.ti.com SBAS482A –JANUARY 2010–REVISED MAY 2010
Auto-Single with Sleep Mode
This mode can be used with the onboard digital
comparator to periodically monitor the status of an
This mode automatically converts the selected
input signal while saving power between conversions.
channel repeatedly with a sleep interval between
Little support is needed from a host microcontroller. It
conversions, as shown in Figure 27. After the ADC
is suggested to stop this mode by setting the mode to
Mode Control register is written, the power-up time
Idle or stopping the conversion by configuring the
(t
PU
) is allowed to elapse. This value can be set to '0'
alarm to do so, before retrieving data. The length in
to effectively bypass if not needed. Before the
time of the cycle (t
CYCLE
) sets the average power
conversion, an acquisition time (t
ACQ
) is allowed to
dissipation, as shown in Figure 3 or Figure 4.
elapse. t
ACQ
time is programmable through the
ACQCONFIG register, bits[4:0]. After the conversion,
sleep time (t
SLEEP
) is allowed to elapse and then the
cycle repeats. The length of the sleep time is
controlled by register bits. During the sleep mode,
power dissipation is minimal and the PWRCON
output is always disabled.
(1) Same channel is continuously converted.
(2) Busy is an internal signal shown as active high that can be routed to the INT pin for external monitoring.
(3) PWRCON is shown enabled and active high.
(4) The mode begins on the trailing edge of the I
2
C acknowledge after writing to the MODECNTL register.
Figure 27. Auto-Single with Sleep Operation Example
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