Analog Devices Inc. AD9845AJST

Overview

AD9845AJST from Analog Devices is a complete 12-bit, 30 MSPS CCD signal processor IC for analog front-end conditioning of interlaced and progressive-scan CCD outputs. It integrates correlated double sampling (CDS), 6-bit pixel gain amplifier (PxGA®), 10-bit variable gain amplifier (VGA) with 2 dB–36 dB range, black-level clamp, and 12-bit ADC - all operating from a single 3 V supply and dissipating 140 mW in normal mode. It is used in digital still cameras and industrial imaging systems requiring high-fidelity analog signal chain integration.

For engineers reviewing the AD9845AJST datasheet, AD9845AJST pinout, AD9845AJST application, or AD9845AJST equivalent, key selection considerations include its 48-lead LQFP package, CCD-mode timing compliance (SHP/SHD rising-edge sampling, 33 ns max DATACLK period), PxGA color steering modes (e.g., Mosaic Separate, Interlace), and auxiliary input support (AUX1IN/AUX2IN) for analog video processing.

Technical Context

The AD9845AJST implements a single-channel CCD signal chain with CDS sampling synchronized to SHP (reference level) and SHD (data level) rising edges, featuring 3 ns internal aperture delay and 9-cycle pipeline latency. Its PxGA supports seven programmable color steering modes (e.g., Bayer mosaic, interlace, 3-color, VD-selected) driven by HD/VD sync inputs and controlled via six 6-bit gain registers.

The VGA provides 1024-step gain control across two regions: codes 0–511 follow a (1+x)/(1−x) log-linear curve (−0.4 dB offset), while codes 512–1023 use linear-in-dB scaling (0.0354 dB/step); guaranteed accuracy applies only to codes 91–1023 (2 dB–36 dB). Clamp operation uses CLPOB/CLPDM clocks to adjust ADC output to user-programmed 8-bit black level (0–255 LSB).

Key Specifications

Pinout & Package

AD9845AJST is housed in a 48-lead thin plastic quad flatpack (LQFP), ST-48 package (θ_JA = 92°C/W), with exposed pad thermal design and lead-free RoHS-compliant finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9846AJST and TDA9981HN/C1, AD9845AJST uniquely balances single-channel CCD optimization, 12-bit precision, PxGA-based color correction, and low-power 3 V operation - making it the most direct fit for compact, high-fidelity monocular imaging systems without digital output requirements.

Availability

AD9845AJST is available at Aetrix Electronics and suitable for digital still cameras, industrial imaging systems, and machine vision inspection requiring stable component supply, long-term lifecycle support, and traceable sourcing for production programs.

Supply support for AD9845AJST 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 AD9845A product line was designed specifically for CCD-based imaging front ends, delivering integrated CDS, pixel-level gain control, and high-speed digitization in a single 3 V, low-power package for portable and industrial vision applications.

FAQ

What is the maximum supported DATACLK frequency for AD9845AJST?

The AD9845AJST supports a maximum DATACLK frequency of 30 MHz, corresponding to a minimum clock period of 33 ns. This timing aligns with its 30 MSPS ADC sampling rate and ensures full functionality in CCD, AUX1, and AUX2 modes. Exceeding this limit risks setup/hold violations on D0–D11 outputs and may cause data corruption or loss of CDS synchronization.

How does the PxGA function in AD9845AJST, and what gain resolution does it provide?

The PxGA in AD9845AJST provides four independently programmable gain values (GAIN0–GAIN3), each adjustable from −2 dB to +10 dB in 64 monotonic steps (6-bit resolution). These gains are applied pixel-by-pixel based on HD/VD timing and selected color steering mode (e.g., Mosaic Separate), enabling per-pixel color correction and white balance without host processor intervention.

Can AD9845AJST operate with analog video inputs other than CCD signals?

Yes, AD9845AJST supports two auxiliary analog input modes: AUX1IN accepts signals with VGA gain up to 36 dB and 2.0 V_p-p output range, while AUX2IN supports up to 18 dB VGA gain. Both modes bypass CDS and PxGA, routing directly to the VGA and ADC - making them suitable for standard composite or component video sources in multi-input imaging systems.

What is the purpose of the CLPOB and CLPDM pins on AD9845AJST?

CLPOB (Black Level Clamp Clock) triggers the optical black clamp loop during shielded black pixel intervals to correct residual DC offsets and track low-frequency black level drift. CLPDM (Input Clamp Clock) enables line-rate input clamping on CCDIN during dummy or optical black pixels to remove large CCD black-level offsets early in the signal chain - preserving headroom for subsequent VGA stages.

Does AD9845AJST support power-down modes, and how quickly does it recover?

Yes, AD9845AJST offers three power-down modes: Fast Recovery (90 mW, 0.1 ms wake-up), Standby (5 mW, 1 ms), and Total Power-Down (1 mW, 3 ms). Recovery is initiated by deasserting STBY or exiting power-down via serial register write; all internal bias and timing circuits stabilize within the specified time, ensuring deterministic resumption of sampling without external reset.