Datasheet

AD5590
Rev. A | Page 32 of 44
The bias generator of the selected DAC(s), output amplifier,
resistor string, and other associated linear circuitry are shut
down when the power-down mode is activated. The internal
reference is powered down only when all channels are powered
down. However, the contents of the DAC register are unaffected
when in power-down. The time to exit power-down is typically
4 µs for DACV
DD
= 5 V.
Any combination of DACs can be powered up by setting PD1
and PD0 to 0 (normal operation). The output powers up to the
value in the input register (
LDAC
low) or to the value in the
DAC register before powering down (
LDAC
high).
DAC Clear Code Register
The DAC blocks have a hardware
CLR
pin that is an asynchron-
ous clear input for all 16 DACs. The
CLR
input is falling edge
sensitive. Bringing the
CLR
line low clears the contents of the
input register and the DAC registers to the data contained in
the user-configurable
CLR
register and sets the analog outputs
accordingly. This function can be used in system calibration to
load zero scale, midscale, or full scale to all channels together.
These clear code values are user-programmable by setting Bit DB1
and Bit DB0 in the
CLR
control register (see Table 17). The
default setting clears the outputs to 0 V. Command 0101 is
reserved for loading the clear code register (see Table 11).
The DAC exits clear code mode on the 32
nd
falling edge of
the next write to the DAC. If
CLR
is activated during a write
sequence, the write is aborted.
The
CLR
pulse activation time—the falling edge of
CLR
to
when the output starts to change—is typically 280 ns. However,
if outside the DAC linear region, it typically takes 520 ns after
executing
CLR
for the output to start changing.
See Table 18 for contents of the input shift register during the
loading clear code register operation.
Table 15. DAC Power-Down Modes of Operation
DB9 DB8 Operating Mode
0 0 Normal operation
Power-down modes:
0 1 1 kΩ to GND
1 0 100 kΩ to GND
1 1 Three-state
Table 16. DAC 32-Bit Input Shift Register Contents for Power-Down/Power-Up Function
MSB LSB
DB31 to
DB28
DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20
DB19
to DB10
DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
X 0 1 0 0 X X X X X PD1 PD0
DAC
H
DAC
G
DAC
F
DAC
E
DAC
D
DAC
C
DAC
B
DAC
A
Don’t care Command bits (C3 to C0)
Address bits (A3 to A0)—
don’t care
Don’t
care
Power-down
mode
Power-down/power-up channel selection—set bit to 1
to select
Table 17. DAC Clear Code Register
Clear Code Register
DB1 DB0
CR1 CR0 Clears to Code
0 0 0x0000
0 1 0x0800
1 0 0x0FFF
1 1 No operation
Table 18. DAC 32-Bit Input Shift Register Contents for Clear Code Function
MSB LSB
DB31 to DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 to DB2 DB1 DB0
X 0 1 0 1 X X X X X CR1 CR0
Don’t care Command bits (C3 to C0) Address bits (A3 to A0)—don’t care Don’t care Clear code register