AD7840KN

Overview

The AD7840KN is a complete 14-bit voltage output digital-to-analog converter (DAC) fabricated in LC2MOS technology. It integrates a 14-bit DAC, a 3 V buried Zener reference, an output amplifier, and high-speed control logic. The device supports both parallel and serial interfaces, enabling direct connection to high-speed DSPs like the ADSP-2100 and TMS320 series. It operates from ±5 V supplies with typical power dissipation of 70 mW. The analog output provides a bipolar range of ±3 V. Key dynamic specifications include a minimum signal-to-noise ratio of 80 dB and total harmonic distortion of -80 dB. The part is housed in a 24-pin plastic DIP package and functions within a commercial temperature range of 0 °C to +70 °C.

Feature Summary

• Complete 14-bit voltage output DAC with integrated 3 V reference and output buffer
• Dual interface capability: 14-bit parallel mode with 21 ns setup time or serial mode up to 6 MHz clock
• High dynamic performance: 80 dB min SNR and -80 dB max THD at 1 kHz
• Low power consumption: typically 70 mW at ±5 V supplies

Applications

• Direct interfacing with high-speed DSP processors such as ADSP-2100 and TMS32010/20
• Speech synthesis systems requiring precise waveform generation
• Servo control loops needing fast settling times and monotonicity
• High-speed modem applications utilizing DAC for signal modulation

Procurement Notes

Verify the ordering suffix 'KN' corresponds to the 24-pin Plastic DIP (N-24) package with a commercial temperature range (0 °C to +70 °C), 80 dB minimum SNR, and ±1 LSB maximum integral nonlinearity. Confirm that the component is leaded and not RoHS compliant based on historical manufacturing data for this specific suffix. Ensure ESD precautions are observed during handling due to the sensitivity of the CMOS input structure.

Selection Notes

Select the AD7840KN when a complete 14-bit solution with an internal reference is required to minimize external component count. Choose this variant over the JN version if higher dynamic performance (80 dB SNR vs 78 dB) and tighter linearity (±1 LSB INL vs ±2 LSB) are necessary. Verify that the ±5 V supply rails match the system design, as the device is not specified for single-supply operation. Consider the serial interface option only if pin count reduction is critical, noting that the CS pin must be tied to VSS.

Part Context

The AD7840 belongs to Analog Devices' LC2MOS family of complete DACs, which combine precision bipolar circuits with low-power CMOS logic. This technology allows for high speed and low power consumption while maintaining accuracy. The KN suffix denotes a specific grade within the AD7840 lineup, offering improved dynamic specifications compared to the standard J-grade parts. It is designed for applications where board space is limited and direct processor interfacing is preferred over multiplexed solutions.

Replacement Considerations

The AD7840JN is a compatible alternative with similar functionality but lower dynamic specs (78 dB SNR, ±2 LSB INL). For quad-channel requirements, the AD7834 or AD7836 may be considered, though they differ in channel count and interface logic. No direct single-source replacement with identical pinout and enhanced specs is publicly documented; redesign may be necessary for upgraded performance.