AD74115 datasheet(34/103 Pages) AD

34 / 103 page

Data Sheet

AD74115

THEORY OF OPERATION

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Rev. 0 | 34 of 103

Open-Circuit Detection

In current output mode, if the headroom voltage falls below the

compliance voltage (specified in Table 2), due to an open-loop

circuit on the channel, a current output open-circuit error is flagged

for that channel, and the ALERT pin asserts. If VAVDD is insufficient

to drive the programmed current output, the open-circuit error is

flagged.

Interpreting ADC Data

In current output mode, the ADC, by default, is configured to

measure the voltage across the screw terminals (I/OP to I/ON) in a

0 V to 12 V range. Use the ADC measurement result to calculate

the voltage across these screw terminals by using the following

equation:

VADC = (ADC_CODE/65,536) × Voltage Range

where:

VADC is the measured voltage in volts.

ADC_CODE is the value of the ADC_RESULT1 register.

Voltage Range is the measurement range of the ADC and is 12 V.

Voltage Input

In voltage input mode, the voltage across the screw terminals

(I/OP to I/ON) is measured by the ADC via the SENSELF and the

AGND_SENSE pins. It is essential to connect the AGND_SENSE

pin as close as possible to the I/ON screw terminal to ensure an

accurate voltage measurement. Figure 31 shows the current and

measurement paths of the voltage input mode.

In voltage input mode, the voltage can be measured in a ±12 V

range. However, there is also an option to measure the I/OP screw

terminal voltage using the diagnostics function. The diagnostics

function allows the voltage to be measured across the full supply

rails.

Figure 31. Voltage Input Mode Configuration

AD74115 Datasheet(PDF) 34 Page - Analog Devices