AD7809BST

Overview

The AD7809BST is an octal 10-bit digital-to-analog converter manufactured by Analog Devices Inc. It features parallel loading capabilities and operates from a +3.3 V to +5 V power supply with an on-chip reference. The device integrates four main DACs and four sub-DACs, allowing individual channel control via system and channel registers. Key electrical parameters include a maximum relative accuracy of –4 LSB (C Grade) or –3 LSB (B Grade), a typical voltage output settling time of 1.5 ms, and a nominal REF OUT voltage of 1.23 V. Power consumption in normal mode is typically 18 mA.

Feature Summary

• Octal configuration with eight 10-bit DAC channels and four 8-bit sub-DACs for transfer function shifting.
• Parallel data interface with double-buffered DAC registers for simultaneous updates via LDAC.
• Integrated 1.23 V bandgap reference with dual external reference capability via REFIN.
• Low power CMOS construction with System Standby and Power-Down modes.

Applications

• Optical disk drives
• Process control and voltage setpoint control systems
• Automatic calibration circuits

Procurement Notes

Verify the specific grade (B or C) and package suffix against the ordering guide. Confirm that the application supports the parallel interface timing requirements, specifically the write pulsewidth and setup/hold times defined in the datasheet. Ensure ESD precautions are observed during handling.

Selection Notes

Select this component when multiple analog outputs are required in a single package with parallel bus connectivity. The B Grade offers tighter accuracy specifications compared to the C Grade. Consider the TQFP-44 package constraints if board space is limited. Verify that the load resistance meets the minimum 2 kΩ requirement.

Part Context

The AD7809 is part of the AD7804/AD7805/AD7808/AD7809 family of 10-bit DACs. While the AD7804 and AD7808 utilize serial interfaces, the AD7809 provides parallel loading. All variants share similar internal architectures, including the Sub DAC functionality and control register structures, differing primarily in input method and channel count.

Replacement Considerations

Public confirmed substitute part numbers: None identified in verified source material.

FAQ

What is the function of the Sub DAC?

The Sub DAC allows the complete transfer function of each Main DAC to be shifted around the VBIAS point, enabling precise adjustment of the output voltage range and offset.

How is simultaneous update of all DAC outputs achieved?

All DACs contain double-buffered data inputs. Taking the LDAC input low simultaneously updates all analog outputs with the contents of their respective data registers.

What coding schemes are supported?

The device supports Twos Complement and Offset Binary input coding schemes, selectable via the BIN/COMP bit in the system control register.