Analog Devices Inc. AD9842AJST

Overview

AD9842AJST from Analog Devices is a complete 12-bit, 20 MSPS CCD signal processor IC featuring correlated double sampling (CDS), 6-bit pixel gain amplifier (PxGA®), 10-bit variable gain amplifier (VGA) with 2 dB to 36 dB range, black-level clamp, and integrated 3-wire serial interface - all operating from a single 3 V supply. It targets high-fidelity analog signal conditioning in interlaced/progressive-scan CCD imaging systems.

For engineers reviewing the AD9842AJST datasheet, AD9842AJST pinout, AD9842AJST application, or AD9842AJST equivalent, this page delivers verified technical context, exact pin functions for LQFP-48, real-world use cases in digital camcorders and industrial vision, and validated alternative parts with documented functional trade-offs.

Technical Context

The AD9842AJST implements a fully integrated analog front-end optimized for CCD output processing: its CDS stage uses SHP/SHD rising-edge sampling with 3 ns internal delay; PxGA supports seven programmable color steering modes (e.g., Bayer mosaic) with per-pixel gain switching; VGA provides monotonic 1024-step gain control across 2–36 dB; and the 12-bit ADC delivers ±0.5 LSB DNL and 0.6 LSB_rms total output noise at 6 dB gain.

It operates in three distinct input modes - CCD, AUX1, and AUX2 - each with dedicated timing, gain ranges (e.g., 0–36 dB in AUX1, 0–18 dB in AUX2), and power consumption (78 mW typical in CCD mode, 60 mW in AUX modes). Clamp level resolution is 256 steps, measured at ADC output, with full-scale range of 0–255 LSB for AD9842A.

Key Specifications

Pinout & Package

AD9842AJST is housed in a 48-lead thin plastic quad flatpack (LQFP, ST-48) with exposed pad (not electrically connected), lead pitch 0.5 mm, body size 7 mm × 7 mm. Pin 1 identifier located at top-left corner (counterclockwise numbering).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CCD signal processor applications.

Compared with AD9841AJST, AD9842AJST adds 2 bits of resolution and doubles clamp granularity - directly improving shadow detail retention and black-level stability. Versus TDC1308IPWPR, it trades raw ADC precision for full integration, reducing BOM count and layout complexity in volume imaging systems.

Availability

AD9842AJST is available at Aetrix Electronics and suitable for digital camcorders, industrial machine vision systems, and automotive rear-view cameras requiring stable component supply, long-term manufacturability, and guaranteed lot traceability.

Supply support for AD9842AJST includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD984x family was designed specifically for CCD-based imaging systems - integrating CDS, PxGA, VGA, clamp, and ADC into a single 3 V device to replace multi-chip AFE solutions in digital still/video cameras and industrial scanners.

FAQ

What is the ADC resolution and architecture of the AD9842AJST?

The AD9842AJST features a true 12-bit successive-approximation register (SAR) ADC with ±0.5 LSB differential nonlinearity and guaranteed no missing codes across all 4096 levels. Its architecture integrates directly after the VGA and clamp stages, accepting a 2.0 V full-scale input range with straight-binary coding. This resolution enables high-fidelity digitization of CCD outputs in applications like digital camcorders where dynamic range and tonal gradation are critical - a key differentiator from the 10-bit AD9841AJST.

How does the PxGA function in the AD9842AJST, and what color filter arrays does it support?

The PxGA in AD9842AJST is a 6-bit, four-value programmable gain amplifier that applies pixel-specific gain based on color steering logic. It supports seven modes - including Mosaic Separate (Bayer), Interlace, 3-Color, 4-Color, VD Selected, Mosaic Repeat, and User-Specified - configured via the Control Register. Each mode maps HD/VD timing to one of four gain registers (Gain0–Gain3), enabling hardware-level white balance and color channel equalization without host processor involvement - a capability confirmed in AD9842AJST's functional block diagram and timing figures.

What are the power consumption characteristics of the AD9842AJST in different operating modes?

AD9842AJST consumes 78 mW typical in CCD mode at 3.0 V and 20 MSPS, 60 mW in both AUX1 and AUX2 modes, and drops to 30 mW in fast recovery power-down, 5 mW in standby, and 1 mW in total shutdown. These values are measured under specified conditions (T_A = 25°C, f_DATACLK = 20 MHz) and reflect actual silicon behavior - not estimates. The low 1 mW shutdown current makes AD9842AJST suitable for battery-backed imaging systems requiring rapid wake-up with minimal quiescent drain.

Does the AD9842AJST support multiple input signal sources, and how are they selected?

Yes, AD9842AJST supports three input configurations: CCD mode (via CCDIN pin), AUX1 mode (via AUX1IN), and AUX2 mode (via AUX2IN), selected by bits in the Channel Select register. CCD mode enables full CDS/PxGA/VGA signal chain; AUX1 retains VGA and clamp but disables CDS and PxGA; AUX2 further restricts VGA to 0–18 dB with 512-step resolution. All modes share the same 12-bit ADC and serial interface - allowing flexible reuse in multi-sensor platforms without redesigning the digital interface.

What is the purpose and implementation of the black-level clamp in the AD9842AJST?

The AD9842AJST implements an active black-level clamp at the analog input stage - not post-VGA - using CLPOB and CLPDM clock inputs to sample optical black pixels. With 256-step resolution (0–255 LSB, measured at ADC output), it removes CCD-specific offset before gain amplification, preventing "gain step" artifacts and maximizing signal headroom. This architecture is explicitly confirmed in the product description, specifications table, and Figure 25 signal chain diagram - distinguishing AD9842AJST from AFEs that perform clamping after VGA.