AD1843JS

Overview

The AD1843JS is a serial-port 16-bit SoundComm codec manufactured by Analog Devices Inc. in an 80-lead PQFP package (S-80 option). It integrates stereo sigma-delta ADCs and quad sigma-delta DACs, supporting V.34/V.32bis modem standards alongside audio functions. The device operates from +5V or mixed +5V/+3V supplies with a total power consumption of 1250 mW at 5.0V. It features programmable sample rates from 4 kHz to 54 kHz derived from a 24.576 MHz clock input. Audio dynamic range exceeds 80 dB, with THD+N typically -74 dB. The codec includes three on-chip PLLs for synchronization and supports FIFO-buffered serial digital interfaces compatible with ADSP-21xx DSPs.

Feature Summary

• Supports simultaneous operation of four different sample rates without beat frequency noise issues using Continuous Time Oversampling technology.
• Integrates three on-chip phase lock loops for synchronization to external signals, including video clocks.
• Provides extensive analog mixing capabilities with thirteen analog inputs and seven analog outputs, including programmable gain and mute functions.
• Features advanced digital signal processing with dual digital resamplers and programmable input/output phase and frequency control.

Applications

• High-performance DSP-based telephony systems requiring integrated speech and modem codecs.
• Voice over data communication products supporting V.34 and V.32bis standards.
• Integrated audio/modem/fax devices requiring simultaneous distinct sample rate operations.
• Echo-cancelling speakerphones utilizing dual independent audio inputs and stereo output.

Procurement Notes

Verify the specific ordering suffix S-80 confirms the 80-lead PQFP package configuration. Ensure the temperature range matches the required operational environment, as this variant is specified for 0°C to +70°C. Confirm supply voltage requirements align with the +5V or mixed +5V/+3V specifications before integration into the final system design.

Selection Notes

Select this component when simultaneous multi-rate audio and modem processing is required within a single chip. It is suitable for applications needing on-chip synchronization via PLLs to external video or clock signals. Consider the 80-lead PQFP package constraints and thermal resistance characteristics during PCB layout planning for optimal heat dissipation.

Part Context

The AD1843JS belongs to the AD1843 SoundComm family, representing one of the first codecs capable of supporting four simultaneous sample rates. It builds upon the functionality of the AD1848 SoundPort but adds significant modem and fax capabilities. This integration reduces system complexity and power consumption for high-performance telephony and audio applications.

Replacement Considerations

The AD1843JST is a pin-compatible alternative featuring a 100-lead TQFP package instead of the 80-lead PQFP. Verify package dimensions and pinout compatibility if substituting between these two variants.

FAQ

How does the AD1843 handle multiple sample rates simultaneously?

It utilizes Analog Devices’ Continuous Time Oversampling (CTO) technology to support four different sample rates simultaneously without generating beat frequency noise issues.

What is the function of the SYNC pins?

The SYNC pins serve as clock source inputs to three receptive phase lock loops (PLLs), allowing the device to synchronize its A-to-D and D-to-A conversions to external signals.

Can the AD1843 operate with mixed supply voltages?

Yes, the device supports operation from a single +5V supply or mixed +5V/+3V supplies, allowing for lower digital power consumption when using a 3.0V digital supply.