Datasheet

AD7266
Rev. B | Page 20 of 28
FULL POWER-DOWN MODE
This mode is intended for use in applications where throughput
rates slower than those in the partial power-down mode are
required, as power-up from a full power-down takes substan-
tially longer than that from partial power-down. This mode is
more suited to applications where a series of conversions
performed at a relatively high throughput rate are followed by a
long period of inactivity and thus power-down. When the
AD7266 is in full power-down, all analog circuitry is powered
down. Full power-down is entered in a similar way as partial
power-down, except the timing sequence shown in Figure 35
must be executed twice. The conversion process must be
interrupted in a similar fashion by bringing
CS
high anywhere
after the second falling edge of SCLK and before the 10
th
falling
edge of SCLK. The device enters partial power-down at this
point. To reach full power-down, the next conversion cycle
must be interrupted in the same way, as shown in .
Once
Figure 37
CS
is brought high in this window of SCLKs, the part
completely powers down.
Note that it is not necessary to complete the 14 SCLKs once
CS
is brought high to enter a power-down mode.
To exit full power-down and power up the AD7266, a dummy
conversion is performed, as when powering up from partial
power-down. On the falling edge of
CS
, the device begins to
power up and continues to power up, as long as
CS
is held low
until after the falling edge of the 10
th
SCLK. The required
power-up time must elapse before a conversion can be initiated,
as shown in . See the section for the
power-up times associated with the AD7266.
Figure 38 Power-Up Times
SCLK
CS
D
OUT
A
D
OUT
B
INVALID DATA
VALID DATA
11014 141
THE PART BEGINS
TO POWER UP.
THE PART IS FULLY
POWERED UP; SEE
POWER-UP TIMES
SECTION.
t
POWER-UP1
04603-031
Figure 36. Exiting Partial Power-Down Mode
THREE-STATE
110142
SCLK
CS
D
OUT
A
D
OUT
B
THREE-STATE
1102
INVALID DATAINVALID DATA
THE PART BEGINS
TO POWER UP.
THE PART ENTERS
PARTIAL POWER DOWN.
THE PART ENTERS
FULL POWER DOWN.
04603-032
14
Figure 37. Entering Full Power-Down Mode