AD7228CQ

Overview

The AD7228CQ is an octal 8-bit voltage-mode digital-to-analog converter (DAC) fabricated on LC2MOS technology. It integrates eight DACs with output buffer amplifiers and interface logic on a single chip, eliminating the need for external trims. The device features individual latches for each channel, controlled via a common 8-bit parallel data bus and three address lines (A0-A2). It supports both single-supply (13.5 V to 16.5 V) and dual-supply (VDD: 10.8 V to 16.5 V; VSS: -5.5 V to -4.5 V) operation. Key electrical specifications include a settling time of 5 µs to ±1/2 LSB, a maximum power dissipation of 1 W, and an operating temperature range of -40°C to +85°C.

Feature Summary

• Octal architecture with eight independent 8-bit DACs and integrated output buffers.
• Microprocessor-compatible parallel interface with TTL/CMOS levels and 95 ns write pulse support.
• Flexible power supply options supporting single (+15 V) or dual (+15 V/-5 V) configurations.
• Guaranteed monotonic performance with ±1 LSB DNL and ±1 LSB INL for the C version.

Applications

• Automated test equipment requiring multi-channel signal generation.
• Industrial process control systems utilizing microprocessor interfaces.
• Programmable power supplies and setpoint controllers.
• Timing deskew circuits in high-speed data acquisition systems.

Procurement Notes

Verify the specific suffix 'CQ' against the manufacturer's current ordering guide, as availability may vary by region. Confirm package type requirements, as the AD7228 family includes PDIP, CERDIP, SOIC, and PLCC variants. Ensure that the design accounts for the 1 W power dissipation limit and appropriate thermal management for the selected package style.

Selection Notes

Select the AD7228CQ when eight isolated 8-bit channels are required with buffered outputs. The 'C' grade offers tighter static accuracy (±1 LSB TUE) compared to the 'K' grade (±2 LSB). Choose this component over unbuffered DACs if direct driving of loads up to 2 kΩ is necessary without external amplification. Verify that the system reference voltage falls within the 2 V to 10 V range for optimal performance.

Part Context

The AD7228 belongs to Analog Devices' LC2MOS family of octal DACs, designed for high-speed integration of digital logic and precision analog circuits. It serves as a multi-channel solution for applications previously requiring multiple discrete converters. The device simplifies board layout by placing all analog inputs/outputs on one side and digital inputs on the other, optimizing trace routing in dense PCB designs.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. When evaluating alternatives, ensure compatibility with the 8-bit resolution, parallel interface protocol, and ±1 LSB linearity specifications. Verify that replacement devices support the same supply voltage ranges and package dimensions if pin-for-pin substitution is required.

FAQ

What is the minimum load resistance for the AD7228CQ outputs?

The minimum load resistance is 2 kΩ when the output voltage is 10 V. The output buffer amplifiers are tested with a 2 kΩ load and 100 pF capacitance.

How does single-supply operation affect the negative-going settling time?

In single-supply operation, the negative-going settling time to voltages near 0 V is slightly longer than in dual-supply operation due to reduced sink capability as the output voltage approaches the ground rail.

Can the AD7228CQ operate with a 5 V single supply?

Yes, the device can operate from a single 5 V supply. However, this results in slightly degraded accuracy performance, and the reference voltage must be limited to maintain the required overhead voltage between VDD and VREF.