EVAL-AD7324CB AD [Analog Devices], EVAL-AD7324CB Datasheet - Page 29

• Manufacturer Part Number: EVAL-AD7324CB
• Description: 4-Channel, Software-Selectable, True Bipolar Input, 12-Bit Plus Sign ADC
• Manufacturer: AD [Analog Devices]

MODES OF OPERATION
The AD7324 has several modes of operation that are designed
to provide flexible power management options. These options
can be chosen to optimize the power dissipation/throughput
rate ratio for different application requirements. The mode of
operation of the AD7324 is controlled by the power manage-
ment bits, Bit PM1 and Bit PM0, in the control register as shown
in
circuitry is fully powered up.
NORMAL MODE
(PM1 = PM0 = 0)
This mode is intended for the fastest throughput rate
performance, with the AD7324 being fully powered up at all
times.
in normal mode.
The conversion is initiated on the falling edge of CS , and the
track-and-hold enters hold mode as described in the Serial
Interface section. Data on the DIN line during the 16 SCLK
transfer is loaded into one of the on-chip registers if the write
bit is set. The register is selected by programming the register
select bits (see
DOUT
SCLK
DIN
CS
Table 11. The default mode is normal mode, where all internal
Figure 46 shows the general operation of the AD7324
SDATA
SCLK
PART IS IN FULL
SHUTDOWN
DIN
CS
Figure 46).
1
CONTROL REGISTER IS LOADED ON THE FIRST 15 CLOCKS,
DATA INTO CONTROL/SEQUENCE/RANGE REGISTER
LEADING ZERO, 2 CHANNEL I.D. BITS, SIGN BIT +
1
Figure 46. Normal Mode
PART BEGINS TO POWER UP ON THE 15TH
SCLK RISING EDGE AS PM1 = PM0 = 0
DATA INTO CONTROL REGISTER
CONVERSION RESULT
PM1 = 0, PM0 = 0
INVALID DATA
Figure 47. Exiting Full Shutdown Mode
16
16
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t
POWER-UP
The AD7324 remains fully powered up at the end of the
conversion if both PM1 and PM0 contain 0 in the control
register.
To complete the conversion and access the conversion result
16 serial clock cycles are required. At the end of the conversion,
CS can idle either high or low until the next conversion.
Once the data transfer is complete, another conversion can be
initiated after the quiet time, t
FULL SHUTDOWN MODE
(PM1 = PM0 = 1)
In this mode, all internal circuitry on the AD7324 is powered
down. The part retains information in the registers during full
shutdown. The AD7324 remains in full shutdown mode until
the power management bits, Bit PM1 and Bit PM0, in the
control register are changed.
A write to the control register with PM1 = 1 and PM0 = 1 places
the part into full shutdown mode. The AD7324 enters full shut-
down mode on the 15
control register is updated.
If a write to the control register occurs while the part is in full
shutdown mode with the power management bits, Bit PM1 and
Bit PM0, set to 0 (normal mode), the part begins to power up
on the 15
updated. Figure 47 shows how the AD7324 is configured to exit
full shutdown mode. To ensure the AD7324 is fully powered up,
t
CS falling edge
THE PART IS FULLY POWERED UP
ONCE
TO KEEP THE PART IN NORMAL MODE, LOAD PM1 = PM0 = 0
POWER-UP
1
CHANNEL IDENTIFIER BITS + CONVERSION RESULT
t
POWER-UP
for full shutdown mode should elapse before the next
th
SCLK rising edge once the control register is
DATA INTO CONTROL REGISTER
HAS ELAPSED
IN CONTROL REGISTER
th
SCLK rising edge rising edge once the
QUIET
, has elapsed.
16
AD7324