AD7804BN

Overview

The AD7804BN is a quad 10-bit digital-to-analog converter (DAC) from Analog Devices, housed in a 16-lead Plastic DIP package. It operates on a single +3.3 V to +5 V supply and features serial loading capabilities via FSIN, CLKIN, and SDIN pins. The device integrates an on-chip bandgap reference outputting typically 1.23 V and includes double-buffered DAC registers for simultaneous updates. Key electrical specifications include a maximum settling time of 4 ms (typically 1.5 ms), a gain error of ±3% FSR, and relative accuracy of ±3 LSBs. It supports power-down modes with current consumption as low as 0.8 mA at +25°C.

Feature Summary

• Quad 10-Bit Resolution: Contains four independent 10-bit DACs within a single package.
• Serial Interface: Utilizes a synchronous serial interface requiring only three control lines (FSIN, CLKIN, SDIN).
• Integrated Reference: Includes an internal bandgap reference with a nominal output voltage of 1.23 V.
• Dual Power Supply Operation: Designed for operation with analog and digital supplies ranging from +3.3 V to +5 V.

Applications

• Optical Disk Drives
• Instrumentation and Communication Systems
• Process Control and Voltage Setpoint Control
• Trim Potentiometer Replacement
• Automatic Calibration

Procurement Notes

Verify the specific suffix 'BN' corresponds to the 16-lead Plastic DIP (N-16) package when sourcing replacements. Confirm that the application requires serial data input rather than parallel loading, which distinguishes this model from the AD7805 series. Ensure supply voltages remain within the specified +3.3 V to +5.5 V range to maintain performance guarantees.

Selection Notes

Select the AD7804BN when space efficiency is required for multiple low-resolution channels using a microcontroller or DSP with limited I/O pins. The serial interface reduces pin count compared to parallel alternatives like the AD7805. Consider the 1.5 ms typical settling time and ±3 LSB accuracy for applications where moderate speed and precision are sufficient.

Part Context

The AD7804 belongs to the AD7804/AD7805/AD7808/AD7809 family of 10-bit DACs. While the AD7804 offers quad serial channels, the AD7808 provides octal serial channels, and the AD7805/AD7809 variants offer parallel loading interfaces. All members share similar electrical characteristics and power supply requirements but differ in channel count and data input methods.

Replacement Considerations

Direct functional substitutes within the same package include the AD7804BR (SOIC-16). For different packages, the AD7804BN is the PDIP variant. Parallel-loading equivalents with identical electrical specs are the AD7805BN (Quad) and AD7809BST (Octal), though interface changes require schematic modifications.

FAQ

What is the function of the COMP pin?

The COMP pin provides an output from the internal AVDD/2 divider and is intended for AC bypass purposes. It should be decoupled with 1 nF capacitors to both AVDD and AGND.

How does the LDAC pin operate?

LDAC is an active-low input that simultaneously updates all DAC registers with the contents of the data registers. If tied permanently low, updates occur automatically on the sixteenth falling clock edge of the serial data stream.

What coding schemes are supported?

The device supports two input coding schemes selectable via the System Control Register: Two's Complement and Offset Binary.