Datasheet

V X
OUT
Amplifier
Resistor
String
DAC
Power-Down
Circuitry
Resistor
Network
DAC8565
SBAS411C –JUNE 2007–REVISED MARCH 2011 www.ti.com
POWER-DOWN MODES DACs. However, for the three power-down modes,
the supply current falls to 1.3μA at 5.5V (0.5μA at
The DAC8565 has two separate sets of power-down
3.6V). Not only does the supply current fall, but the
commands. One set is for the DAC channels and the
output stage also switches internally from the output
other set is for the internal reference. For more
of the amplifier to a resistor network of known values.
information on powering down the reference, see the
Enable/Disable Internal Reference section. The advantage of this switching is that the output
impedance of the device is known while it is in
DAC Power-Down Commands power-down mode. As described in Table 7, there are
three different power-down options. V
OUT
can be
The DAC8565 use four modes of operation. These
connected internally to GND through a 1kΩ resistor, a
modes are accessed by setting three bits (PD2, PD1,
100kΩ resistor, or open circuited (High-Z). The output
and PD0) in the shift register. Table 7 shows how to
stage is shown in Figure 96. In other words, DB16,
control the operating mode with data bits PD0
DB15, and DB14 = '111' represent a power-down
(DB16), PD1 (DB15), and PD2 (DB14).
condition with Hi-Z output impedance for a selected
channel. '101' represents a power-down condition
Table 7. DAC Operating Modes
with 1kΩ output impedance, and '110' represents a
PD0 PD1 PD2
power-down condition with 100kΩ output impedance.
(DB16) (DB15) (DB14) DAC OPERATING MODES
0 X X Normal operation
1 0 1 Output typically 1kΩ to GND
1 1 0 Output typically 100 kΩ to GND
1 1 1 Output high-impedance
The DAC8565 treats the power-down condition as
data; all the operational modes are still valid for
power-down. It is possible to broadcast a power-down
condition to all the DAC8565s in a system; it is also
possible to simultaneously power-down a channel
while updating data on other channels.
Figure 96. Output Stage During Power-Down
When the PD0 bit is set to '0', the device works
normally with its typical current consumption of 1mA
All analog channel circuitries are shut down when the
at 5.5V with an input code = 32768. The reference
power-down mode is exercised. However, the
current is included with the operation of all four
contents of the DAC register are unaffected when in
power down. The time required to exit power-down is
typically 2.5μs for V
DD
= 5V, and 5μs for V
DD
= 3V.
See the Typical Characteristics for more information.
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