AD9842AJST

Overview

The AD9842AJST is a complete analog signal processor for CCD applications, featuring a single-channel architecture designed to sample and condition outputs of interlaced and progressive scan area CCD arrays. It operates from a single 3 V power supply with typical power consumption of 78 mW. The device includes a 12-bit A/D converter with a maximum clock rate of 20 MHz. Key specifications include an operating temperature range of -20°C to +85°C, a 48-lead LQFP package, and a 3-wire serial digital interface for register programming.

Feature Summary

• Integrates a 20 MSPS Correlated Double Sampler (CDS) and a true 12-bit A/D converter.
• Includes a Pixel Gain Amplifier (PxGA) with 6-bit gain control and a Variable Gain Amplifier (VGA) with 10-bit resolution.
• Features low noise clamp circuits and an analog preblanking function for signal conditioning.
• Supports auxiliary inputs with VGA and input clamp capabilities for processing analog video signals.

Applications

• Digital Still Cameras
• Digital Video Camcorders

Procurement Notes

Verify the component against official Analog Devices documentation to confirm pinout compatibility and electrical characteristics. Ensure that the specific ordering suffix matches the required package type and temperature range. Cross-reference the manufacturer part number with authorized distributors to validate authenticity and traceability before integration into designs.

Selection Notes

Select this model when a 12-bit ADC resolution is required for CCD signal processing at speeds up to 20 MSPS. Consider the AD9841A variant if 10-bit resolution is sufficient for the application. Evaluate the 48-lead LQFP package constraints and verify that the 3 V single-supply operation aligns with the system power budget and thermal requirements.

Part Context

The AD9842AJST belongs to the AD9841A/AD9842A family of complete CCD signal processors manufactured by Analog Devices. This series provides integrated analog front-end solutions specifically tailored for imaging applications requiring high-speed sampling and precise signal conditioning of CCD array outputs.

Replacement Considerations

The AD9841AJST is a direct functional substitute within the same family, differing only in ADC resolution (10-bit vs. 12-bit). Verify that the reduced resolution meets the system requirements before substitution.

FAQ

What is the difference between the AD9841A and AD9842A?

The primary difference is the ADC resolution; the AD9841A features a 10-bit A/D converter, while the AD9842A contains a true 12-bit A/D converter. Both share the same 20 MSPS architecture and peripheral features.

How is the PxGA gain controlled?

The Pixel Gain Amplifier (PxGA) gain is controlled via a 6-bit digital value loaded through the 3-wire serial interface. It supports four separate gain values that can be multiplexed on a pixel-to-pixel basis using the Color Steering modes.

What is the purpose of the CLPOB and CLPDM pulses?

CLPOB (Black Level Clamp Clock) and CLPDM (Input Clamp Clock) are used to control the low noise clamp circuits. They remove DC offsets from the CCD signal, such as optical black levels, during specific phases of the line timing.