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AD7265
Rev. A | Page 20 of 28
To exit this mode of operation and power up the AD7265 again,
a dummy conversion is performed. 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 10th
SCLK. The device is fully powered up after approximately 1 μs
has elapsed, and valid data results from the next conversion, as
shown in
Figure 36. If CS is brought high before the second
falling edge of SCLK, the AD7265 again goes into partial
power-down. This avoids accidental power-up due to glitches
on the CS line. Although the device may begin to power up on
the falling edge of CS, it powers down again on the rising edge
of CS. If the AD7265 is already in partial power-down mode
and CS is brought high between the second and 10th falling
edges of SCLK, the device enters full power-down mode.
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
substantially 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 AD7265 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 10th 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
Figure 37.Once CS is brought high in this window of SCLKs, the part
completely powers down.
CS
Note that it is not necessary to complete the 14 SCLKs once
is brought high to enter a power-down mode.
To exit full power-down and power up the AD7265, 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 10th SCLK. The required
power-up time must elapse before a conversion can be initiated,
power-up times associated with the AD7265.
SCLK
CS
DOUTA
DOUTB
INVALID DATA
VALID DATA
110
14
1
THE PART BEGINS
TO POWER UP.
THE PART IS FULLY
POWERED UP; SEE
POWER-UP TIMES
SECTION.
tPOWER-UP1
04674-031
Figure 36. Exiting Partial Power-Down Mode
THREE-STATE
110
14
2
SCLK
CS
DOUTA
DOUTB
THREE-STATE
110
2
INVALID DATA
THE PART BEGINS
TO POWER UP.
THE PART ENTERS
PARTIAL POWER DOWN.
THE PART ENTERS
FULL POWER DOWN.
04674-032
14
Figure 37. Entering Full Power-Down Mode