AD5754BREZ datasheet(27/31 Pages) AD

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Data Sheet

AD5724/AD5734/AD5754

Rev. F | Page 27 of 31

FEATURES

ANALOG OUTPUT CONTROL

In many industrial process control applications, it is vital to control

the output voltage 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, Trans-

mission 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 AD5724/AD5734/AD5754 can be

individually powered down. By default, all channels are in power-

down mode. The power status is controlled by the power control

is in power-down mode, the 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 AD5724/AD5734/AD5754 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 the 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 AD5724/AD5734/AD5754 incorporate a thermal shutdown

feature that automatically shuts down the device if the core temp-

erature 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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