AD5752AREZ datasheet(27/31 Pages) AD

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Data Sheet

AD5722/AD5732/AD5752

Rev. F | Page 27 of 31

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 VOUTx 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 analog

power supplies have stabilized and a valid word is written to a

DAC register. At this time, G2 opens and G1 closes.

VOUTA

VOLTAGE

MONITOR

AND

CONTROL

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 27 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 (OCX) bit in the power

control register. Upon removal of the short-circuit fault, the

OCX 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 (OCX) bits, and the

power-up (PUX) bits indicate which DACs have powered down.

After the fault is rectified, the channels can be powered up again

by setting the PUX 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.

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