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Data Sheet

AD5750/AD5750-1/AD5750-2

Rev. D | Page 29 of 36

DETAILED DESCRIPTION OF FEATURES

OUTPUT FAULT ALERT—SOFTWARE MODE

In software mode, the AD5750/AD5750-1/AD5750-2 are equipped

with one FAULT pin; this is an open-drain output allowing several

AD5750/AD5750-1/AD5750-2 devices to be connected together

to one pull-up resistor for global fault detection. In software mode,

the FAULT pin is forced active low by any one of the following

fault scenarios:

•

The voltage at IOUT attempts to rise above the compliance

range due to an open-loop circuit or insufficient power supply

voltage. The internal circuitry that develops the fault output

avoids using a comparator with window limits because this

requires an actual output error before the fault output becomes

active. Instead, the signal is generated when the internal

amplifier in the output stage has less than approximately

1 V of remaining drive capability. Thus, the fault output

activates slightly before the compliance limit is reached.

Because the comparison is made within the feedback loop

of the output amplifier, the output accuracy is maintained

by its open-loop gain, and an output error does not occur

before the fault output becomes active.

•

A short is detected on the voltage output pin (VOUT). The

short-circuit current is limited to 15 mA.

•

An interface error is detected due to PEC failure. See the

Packet Error Checking section.

•

The core temperature of the AD5750/AD5750-1/AD5750-2

exceeds approximately 150°C.

OUTPUT FAULT ALERT—HARDWARE MODE

In hardware mode, the AD5750/AD5750-1/AD5750-2 are

equipped with three fault pins: VFAULT, IFAULT, and TEMP.

These are open-drain outputs allowing several AD5750/AD5750-1/

AD5750-2 devices to be connected together to one pull-up resistor

for global fault detection. In hardware control mode, these fault

pins are forced active by any one of the following fault scenarios:

•

An open circuit is detected. The voltage at IOUT attempts

to rise above the compliance range, due to an open-loop

circuit or insufficient power supply voltage. The internal

circuitry that develops the fault output avoids using a

comparator with window limits because this requires an

actual output error before the fault output becomes active.

Instead, the signal is generated when the internal amplifier

in the output stage has less than approximately 1 V of

remaining drive capability. Thus, the fault output activates

slightly before the compliance limit is reached. Because the

comparison is made within the feedback loop of the output

amplifier, the output accuracy is maintained by its open-

loop gain, and an output error does not occur before the

fault output becomes active. If this fault is detected, the

IFAULT pin is forced low.

•

A short is detected on the voltage output pin (VOUT). The

short-circuit current is limited to 15 mA. If this fault is

detected, the VFAULT pin is forced low.

•

The core temperature of the AD5750/AD5750-1/AD5750-2

exceeds approximately 150°C. If this fault is detected, the

TEMP pin is forced low.

VOLTAGE OUTPUT SHORT-CIRCUIT PROTECTION

Under normal operation, the voltage output sinks and sources

up to 12 mA and maintains specified operation. The maximum

current that the voltage output delivers is 15 mA; this is the

short-circuit current.

ASYNCHRONOUS CLEAR (CLEAR)

CLEAR is an active high clear that allows the voltage output to

be cleared to either zero-scale code or midscale code and is

user-selectable via the CLRSEL pin or the CLRSEL bit of the input

shift register, as described in Table 8. (The clear select feature is

a logical OR function of the CLRSEL pin and the CLRSEL bit).

The current loop output clears to the bottom of its programmed

range. When the CLEAR signal is returned low, the output returns

to its programmed value or to a new programmed value. A clear

operation can also be performed via the clear command in the

control register (see Table 11).

Table 11. CLRSEL Options

CLRSEL

Output Clear Value

Unipolar Output Voltage Range

Unipolar Current Output Range

Bipolar Output Range

Bipolar Current Output Range

0 V

Zero scale; for example,

4 mA on the 4 mA to 20 mA range,

0 mA on the 0 mA to 20 mA range

Negative full scale

Zero scale; for example,

−24 mA on the ±24 mA range

Midscale

Midscale; for example,

12 mA on the 4 mA to 20 mA range,

10 mA on the 0 mA to 20 mA range

0 V

Midscale; for example,

0 mA on the ±24 mA range

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