Datasheet

 2010 Microchip Technology Inc. DS22250A-page 21
MCP4902/4912/4922
4.2.4 SHUTDOWN MODE
The user can shut down each DAC channel selectively
by using a software command or shut down all chan-
nels by using the SHDN
pin. During Shutdown mode,
most of the internal circuits in the channel that was shut
down are turned off for power savings. The serial inter-
face remains active, thus allowing a write command to
bring the device out of the Shutdown mode. There will
be no analog output at the channel that was shut down
and the V
OUT
pin is internally switched to a known
resistive load (500 ktypical. Figure 4-4 shows the
analog output stage during the Shutdown mode.
The condition of the Power-on Reset circuit during the
shutdown is as follows:
a) Turned-off, if the shutdown occurred by the
SHDN
pin;
b) On, if the shutdown occurred by the software.
The device will remain in Shutdown mode until the
SHDN
pin is brought to high or a write command with
<SHDN
> bit = 1 is latched into the device. When a DAC
is changed from Shutdown to Active mode, the output
settling time takes less than 10 µs, but more than the
standard active mode settling time (4.5 µs).
FIGURE 4-4: Output Stage for Shutdown
Mode.
500 k 
Power-Down
Control Circuit
Resistive
Load
V
OUT
Op
Amp
Resistive String DAC