Datasheet

AD5722/AD5732/AD5752
Rev. D | Page 27 of 32
DESIGN FEATURES
ANALOG OUTPUT CONTROL
In many industrial process control applications, it is vital that
the output voltage be controlled during power-up. When the
supply voltages change during power-up, the V
OUT
x pins are
clamped to 0 V via a low impedance path (approximately 4 kΩ).
To prevent the output amplifiers from being shorted to 0 V
during this time, Transmission Gate G1 is also opened (see
Figure 42). These conditions are maintained until the power
supplies have stabilized and a valid word is written to a DAC
register. At this time, G2 opens and G1 closes.
V
OUT
A
G1
G2
VOLTAGE
MONITOR
AND
CONTROL
0
6467-010
Figure 42. Analog Output Control Circuitry
POWER-DOWN MODE
Each DAC channel of the AD5722/AD5732/AD5752 can be
individually powered down. By default, all channels are in
power-down mode. The power status is controlled by the power
control register (see Table 26 and Table 2 7 for details). When a
channel is in power-down mode, its output pin is clamped to
ground through a resistance of approximately 4 kΩ, and the
output of the amplifier is disconnected from the output pin.
OVERCURRENT PROTECTION
Each DAC channel of the AD5722/AD5732/AD5752 incorporates
individual overcurrent protection. The user has two options for
the configuration of the overcurrent protection: constant current
clamp or automatic channel power-down. The configuration of
the overcurrent protection is selected via the clamp enable bit in
the control register.
Constant Current Clamp (Clamp Enable = 1)
If a short circuit occurs in this configuration, the current is
clamped at 20 mA. This event is signaled to the user by the
setting of the appropriate overcurrent (OC
X
) bit in the power
control register. Upon removal of the short-circuit fault, the
OC
X
bit is cleared.
Automatic Channel Power-Down (Clamp Enable = 0)
If a short circuit occurs in this configuration, the shorted channel
powers down and its output is clamped to ground via a resistance
of approximately 4 kΩ. At this time, the output of the amplifier
is disconnected from the output pin. The short-circuit event is
signaled to the user via the overcurrent (OC
X
) bits, and the
power-up (PU
X
) bits indicate which DACs have powered down.
After the fault is rectified, the channels can be powered up again
by setting the PU
X
bits.
THERMAL SHUTDOWN
The AD5722/AD5732/AD5752 incorporate a thermal shutdown
feature that automatically shuts down the device if the core
temperature exceeds approximately 150°C. The thermal shutdown
feature is disabled by default and can be enabled via the TSD
enable bit of the control register. In the event of a thermal
shutdown, the TSD bit of the power control register is set.