AD7846AQ

Overview

The AD7846AQ is a 16-bit voltage output digital-to-analog converter (DAC) manufactured by Analog Devices Inc. Constructed using the LC2MOS process, it features a segmented architecture ensuring monotonicity over temperature. The device includes an on-chip output amplifier configurable for unipolar (0 V to +5 V or +10 V) or bipolar (±5 V or ±10 V) ranges. It operates with analog supplies of ±11.4 V to ±15.75 V and a digital supply of 4.75 V to 5.25 V. Key electrical specifications include ±2 LSB integral linearity error at +25°C, a typical power dissipation of 100 mW, and a settling time of 6 μs to 0.006% FSR. The component supports microprocessor interfacing with readback capability.

Feature Summary

• 16-bit resolution with guaranteed monotonicity over the operating temperature range.
• Integrated readback function allowing access to DAC latch contents via the R/W pin.
• Low power consumption with typical dissipation of 100 mW.
• Configurable output stages supporting unipolar and bipolar voltage ranges.

Applications

• Closed-loop control systems requiring high accuracy.
• Automatic Test Equipment (ATE) utilizing readback diagnostics.
• Position measurement applications involving LVDT interfaces.
• Multiplying DAC configurations for signal processing.

Procurement Notes

Verify the specific package type required, as the AD7846 series is available in 28-lead plastic, ceramic, and PLCC variants. Confirm that the A suffix denotes the extended industrial temperature range of −40°C to +85°C. Ensure supply voltages match the specified limits: VDD/VSS between ±11.4 V and ±15.75 V, and VCC between 4.75 V and 5.25 V. Check for RoHS compliance status if environmental regulations apply to the target assembly.

Selection Notes

Select the AD7846AQ when 16-bit monotonicity and low glitch impulse are critical. The device requires external reference inputs; ensure VREF+ and VREF− are within the allowed range relative to the analog supplies. For bipolar operation, connect VREF− to −5 V. Consider the capacitive load limit of 1000 pF for stability. If simultaneous updating of multiple DACs is needed, utilize the LDAC pin for synchronized data latching.

Part Context

The AD7846 belongs to the AD7846 family of precision DACs from Analog Devices. It utilizes a unique segmented architecture where four MSBs select segments on a resistor string, feeding a 12-bit DAC for interpolation. This design ensures 16-bit monotonicity without requiring tight matching of all resistors. The 'A' suffix indicates the commercial/industrial temperature grade, distinguishing it from military or extended grades.

Replacement Considerations

Public confirmed substitute part numbers are not provided in the verified source material.

FAQ

How does the AD7846 ensure 16-bit monotonicity?

It uses a segmented architecture where the four MSBs select adjacent nodes on a 16-resistor string. These feed a 12-bit DAC which interpolates the voltage. The switching logic ensures that amplifier offset voltages do not cause non-monotonic behavior during segment transitions.

What is the purpose of the CLR pin?

The CLR pin resets the DAC latch contents. When asserted low while R/W is low, it loads 000…000. When asserted low while R/W is high, it loads 100…000. This allows resetting the output to 0 V in both unipolar and bipolar configurations.

Can the AD7846 be used for multiplying operations?

Yes, it is a full multiplying DAC. To achieve four-quadrant multiplication, tie VREF− to 0 V, apply the AC input signal to VREF+, and tie RIN to VREF+.