Analog Devices Inc. AD9840JST

Overview

AD9840JST from Analog Devices is a complete 10-bit, 36 MSPS analog signal processor for CCD imaging systems, integrating input clamp, correlated double sampler (CDS), digitally controlled VGA (2–36 dB gain), black level clamp, and ADC in a single 48-lead LQFP package. It supports interlaced/progressive scan CCD arrays and auxiliary analog video inputs.

For engineers reviewing the AD9840JST datasheet, AD9840JST pinout, AD9840JST application, or AD9840JST equivalent, this device is selected for high-fidelity CCD signal conditioning where precise black-level control, low-noise CDS sampling, and serial register programmability are required in digital still cameras and camcorders.

Technical Context

The AD9840JST implements a single-channel CCD signal chain with dedicated timing-controlled sampling: SHP and SHD clocks drive CDS operation at up to 36 MHz, while CLPOB and CLPDM enable optical black clamping with pixel-level resolution (2–20 pixels). Internal registers configure gain, clamp level, power modes, and input selection via a 3-wire serial interface (SCK ≤ 6 MHz, SL/SDATA/SCK timing validated).

Its analog front-end includes three independent clamp circuits (CCDIN, AUX1IN, AUX2IN), each with programmable clamp level (256-step resolution, 0–63.75 LSB), and a 10-bit ADC guaranteeing no missing codes. Power management supports standby, fast recovery, and total shutdown modes with defined junction temperature limits (150°C max).

Key Specifications

Pinout & Package

AD9840JST is housed in a 48-lead Thin Plastic Quad Flatpack (LQFP), designated ST-48 per Analog Devices' ordering guide. The package is RoHS-compliant, surface-mountable, and features exposed paddle for thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9841JST, AD9840JST offers lower cost and simpler layout but requires external reference decoupling; compared with TDA9980HN/C1, AD9840JST provides CCD-optimized analog conditioning unattainable in general-purpose video processors.

Availability

AD9840JST is available at Aetrix Electronics and suitable for digital still cameras, industrial inspection systems, and medical endoscopy modules requiring stable component supply and long-term obsolescence support.

Supply support for AD9840JST 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, founded in 1965 and headquartered in Wilmington, MA.

The AD9840JST belongs to Analog Devices' CCD signal processor product line, designed specifically to replace multi-chip analog front-ends in professional and industrial imaging systems requiring precision CDS, programmable gain, and black-level control.

FAQ

What is the primary function of the AD9840JST in a CCD imaging system?

The AD9840JST serves as a complete analog signal processor for CCD sensors, performing correlated double sampling (CDS), variable gain amplification (2–36 dB), black-level clamping, and 10-bit analog-to-digital conversion at up to 36 MSPS. Its integrated signal chain replaces discrete op-amps, clamps, and ADCs, reducing board area and improving noise performance in digital still cameras and camcorders. The AD9840JST is configured via a 3-wire serial interface and operates from a single 3.0 V supply.

Does the AD9840JST support both interlaced and progressive scan CCD arrays?

Yes, the AD9840JST supports both interlaced and progressive scan CCD arrays through its flexible timing architecture. Its SHP and SHD clocks synchronize to CCD reference and data levels respectively, while CLPOB and CLPDM allow pixel-accurate black-level clamping across line periods. The AD9840JST's 36 MSPS sampling rate and 9-cycle pipeline delay accommodate high-resolution progressive formats, and its auxiliary input modes (AUX1IN/AUX2IN) extend compatibility to non-CCD analog video sources.

How is black-level clamping implemented in the AD9840JST?

The AD9840JST implements black-level clamping using two dedicated clock inputs: CLPOB for optical black clamping and CLPDM for input clamping. Each clamp operates with 256-step resolution (0–63.75 LSB), adjustable via internal registers. Clamp level is applied to CCDIN, AUX1IN, or AUX2IN depending on channel select mode. The AD9840JST guarantees no missing codes in its 10-bit ADC output, ensuring that clamp-induced DC offsets do not introduce quantization errors in downstream image processing.

What power management features does the AD9840JST offer?

The AD9840JST provides three configurable power-down modes via its Control Register: Fast Recovery (reduces current while retaining register state), Standby (deeper sleep with longer wake-up latency), and Total Shutdown (lowest current draw, requiring full reset on wake-up). These modes are accessed through pin 44 (STBY) and internal register bits. The AD9840JST consumes 140 mW typical at 3.0 V, and its power management enables battery-operated devices to extend runtime without sacrificing signal integrity during active capture.

Is the AD9840JST pin-compatible with other members of the AD984x family?

Yes, the AD9840JST is pin-compatible with AD9841JST, AD9842JST, and AD9843JST within the same 48-lead LQFP (ST-48) package. All share identical pin functions, timing specifications, and register maps. Differences lie in feature sets: AD9841JST adds an integrated DAC, AD9842JST includes dual-channel operation, and AD9843JST adds programmable gamma correction. The AD9840JST serves as the base variant with core CCD signal processing functionality and no added peripherals.