Datasheet

Convert
Channel
First
SelectedChannel Ne Chanxt nel Ne Chanxt nel Ne Chanxt nel
Sleep
Satust
B syu
(1)
Input Multiplexer
t
ACQ
t
CONV
t
SLEEP
Acquire
First
Channel
Convert
Channel
Se ndco
Sleep
t
SLEEP
t
CONV
t
ACQ
t
CYCLE
Convert
Channel
Th rdi
Sleep
t
SLEEP
t
CONV
t
ACQ
Convert
Channel
Fourth
t
CONV
t
ACQ
Acquire
Fourth
Channel
Acquire
Third
Channel
Acquire
Second
Channel
PWRCON
(2)
t
PU
Awake
t
PU
Awake
t
PU
Awake
t
PU
Awake
(3)
ADS7924
SBAS482A –JANUARY 2010–REVISED MAY 2010 www.ti.com
Auto-Scan with Sleep Mode
is stopped. Data from the conversions are always put
into the data register that corresponds to a particular
This mode automatically converts all the channels
channel. For example, CH2 data always goes in
repeatedly with a sleep interval between conversions,
register DATA2_H and DATA2_L regardless of
as illustrated in Figure 28. After the ADC Mode
conversion order.
Control register is written, the power-up time (t
PU
) is
allowed to elapse. This value can be set to '0' to
This mode can be used with the onboard digital
effectively bypass if not needed. Before the first
comparator to periodically monitor the status of the
conversion of the selected input, an acquisition time
input signals while saving power between
(t
ACQ
) is allowed to elapse. t
ACQ
time is programmable
conversions. Little support is needed from a host
through the ACQCONFIG register, bits[4:0]. After the
microcontroller. It is suggested to stop this mode by
conversion, a sleep time (t
SLEEP
) is allowed to elapse
setting the mode to Idle or stopping the conversion by
and then the cycle repeats. The length of the sleep
configuring the alarm to do so, before retrieving data.
time is controlled by register bits. During the sleep
The length in time of the cycle (t
CYCLE
) sets the
mode, power dissipation is minimal and the
average power dissipation, as shown in Figure 3 or
PWRCON output is always disabled. The input
Figure 4.
multiplexer is automatically incremented as the
conversions complete. If, for example, the initial
selected channel is CH2, the conversion order is
CH2, CH3, CH0, CH1, CH2, CH3, etc. until the mode
(1) Busy is an internal signal shown as active high that can be routed to the INT pin for external monitoring.
(2) PWRCON is shown enabled and active high.
(3) The mode begins on the trailing edge of the I
2
C acknowledge after writing to the MODECNTL register.
Figure 28. Auto-Scan with Sleep Operation Example
18 Submit Documentation Feedback Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): ADS7924