Datasheet

Status
Awake
Awaiting
Mode
Selection
Busy
(1)
DataReady
(2)
P RCONW
(3)
Convert
First
Channel
Convert
Second
Channel
Convert
Third
Channel
Convert
Fourth
Channel
In up t Mu ip el et l x r
SelectedChan lne NextCh na nel NextCh na nel NextCh na nel
t
PU
t
ACQ
t
CONV
t
ACQ
t
ACQ
t
ACQ
t
CONV
t
CONV
t
CONV
Acquire
First
Channel
Acquire
Second
Channel
Acquire
Third
Channel
Acquire
Fourth
Channel
(4)
ADS7924
SBAS482A –JANUARY 2010–REVISED MAY 2010 www.ti.com
Manual-Scan Mode
CH2 data always goes in register DATA2_H and
DATA2_L regardless of conversion order. After all
This mode converts all of the channels once, starting
four conversions complete, the device waits for a new
with the selected channel, as illustrated in Figure 24.
mode to be set. This mode can be set to Idle
After the ADC Mode Control register is written, the
afterwards to save power. The INT pin can be
power-up time (t
PU
) is allowed to elapse. This value
configured to indicate the completion of each
can be set to '0' to effectively bypass if not needed.
individual conversion or it can wait until all four finish.
Before each conversion, an acquisition time (t
ACQ
) is
In either case, the appropriate data register is
allowed to elapse. t
ACK
time is programmable through
updated after each conversion. These registers can
the ACQCONFIG register, bits[4:0]. Sleep time
be read at any time afterwards. If multiple scan are
(t
SLEEP
) is not used in this mode. The input
needed, the manual-scan mode can be reissued
multiplexer is automatically incremented as the
without requiring the Awake mode to be issued in
conversions complete. If, for example, the initial
between.
selected channel is CH2, the conversion order is
CH2, CH3, CH0, and CH1. Data from the
conversions are always put into the data register that
corresponds to a particular channel. For example,
(1) Busy is an internal signal shown as active high that can be routed to the INT pin for external monitoring.
(2) Data ready is an internal signal shown as active high and is enabled when all conversions are complete. It 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 24. Manual-Scan Operation Example
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