AD1985JST

Overview

The AD1985JST is an AC '97 2.3 compliant audio codec manufactured by Analog Devices Inc., housed in a 48-lead LQFP package. It features six DAC channels for 5.1 surround sound and 20-bit resolution on all DACs, achieving greater than 90 dB dynamic range. The device includes integrated stereo headphone amplifiers, S/PDIF output, and variable rate audio support up to double rate (96 kHz). Input capabilities include line-level mono phone input, high-quality CD mixer input, selectable MIC input with preamp, AUX, and line-in stereo inputs. Power management modes and jack sensing are supported.

Feature Summary

• AC '97 2.3 compliance with integrated parametric equalizer and auto down-mix functionality
• Advanced jack sense with auto topology switching and peripheral enumeration
• Integrated PLL for system clocking and software-enabled VREFOUT for microphones

Applications

• Desktop PC audio systems requiring 5.1 surround sound
• Laptop computers utilizing advanced jack sense and power management
• Consumer electronics with integrated stereo headphone amplifiers

Procurement Notes

Verify the component authenticity by checking the vendor ID registers (0x7C and 0x7E) against official Analog Devices documentation. Confirm the package type matches the 48-lead LQFP specification. Ensure the revision level corresponds to Rev. A of the datasheet to guarantee functional compatibility with AC '97 2.3 interfaces.

Selection Notes

Select this codec for applications requiring 20-bit DAC resolution and integrated headphone drivers. Consider the AC '97 interface constraints when designing the digital link. Evaluate the power consumption in standby modes if battery life is critical. Verify that the required sample rates, including 96 kHz double rate, align with the system clock capabilities.

Part Context

The AD1985 belongs to the Analog Devices SoundMAX series of audio codecs. It is designed to replace legacy audio solutions by integrating multiple functions into a single chip, reducing board space and component count. The JST suffix indicates the specific tape and reel packaging format used for surface mount assembly.

Replacement Considerations

Direct replacements must maintain AC '97 2.3 compatibility and similar pin configurations. Check for equivalent DAC resolution and integrated headphone amplifier specifications. Verify that the replacement supports the same power supply voltages and jack sensing features.