Analog Devices Inc. AD9804AJST

Overview

AD9804AJST from Analog Devices is a complete 10-bit, 18 MSPS CCD signal processor IC featuring correlated double sampling (CDS), 6 dB to 40 dB digitally programmable VGA, black level clamping, and integrated 3-wire serial interface - all in a 48-lead LQFP package. It conditions analog outputs from interlaced/progressive scan area CCD arrays for PC cameras and digital still cameras.

For engineers reviewing the AD9804AJST datasheet, AD9804AJST pinout, AD9804AJST application, or AD9804AJST equivalent, this page delivers verified technical context, real-world timing constraints, gain register behavior, clamp clock dependencies, and supply decoupling requirements critical for CCD AFE design validation and layout integrity.

Technical Context

The AD9804AJST implements a single-channel analog front-end with sequential CDS sampling at SHP (reference level) and SHD (data level) rising edges, followed by VGA gain adjustment and black-level clamping synchronized to CLPOB/CLPDM pulses. Its internal timing generator supports pixel-rate operation up to 18 MHz with 9-cycle pipeline latency.

All analog functions - including CDS, VGA, clamp circuits, and 10-bit ADC - operate from a single 3.0 V supply, with separate DVDD/DRVDD rails enabling 2.7 V digital driver compatibility. The 3-wire serial interface (SCK/SL/SDATA) programs the 10-bit VGA gain register and supports readback with 5-cycle data valid delay after SCK falling edge.

Key Specifications

Pinout & Package

AD9804AJST is housed in a 48-lead LQFP (ST-48) package with exposed pad, θ_JA = 92°C/W. Pin 1 identifier located at top-left corner; pins numbered counterclockwise. Analog and digital grounds are physically separated but require common low-impedance ground plane per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9804AJST, AD9803ASTZ offers lower power and simpler interface but sacrifices 3 MSPS speed and PBLK functionality; TDA9979HN/C1 provides higher throughput and digital output but increases system complexity and eliminates monolithic analog signal conditioning.

Availability

AD9804AJST is available at Aetrix Electronics and suitable for PC cameras, digital still cameras, and industrial machine vision systems requiring stable component supply, long-lifecycle support, and traceable sourcing for legacy CCD-based designs.

Supply support for AD9804AJST 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 AD9804AJST belongs to Analog Devices' CCD signal processor product line, designed specifically to integrate CDS, VGA, clamping, and ADC functions into a single chip for cost-sensitive, space-constrained imaging applications.

FAQ

What is the absolute maximum clock frequency supported by the AD9804AJST?

The AD9804AJST supports a maximum DATACLK, SHP, and SHD clock frequency of 18 MHz, as specified in the Timing Specifications table. Exceeding this rate violates setup/hold timing margins (e.g., tSHP min = 10 ns) and risks metastability in the CDS latch and ADC sampling stages. Operation beyond 18 MHz is not characterized and may result in missing codes or increased integral nonlinearity. The AD9804AJST must be operated within this limit for guaranteed performance across its full –20°C to +85°C temperature range.

How does the AD9804AJST handle black level clamping during optical black pixel periods?

The AD9804AJST performs black level clamping using CLPOB and CLPDM clock inputs, which trigger internal clamp circuits during optical black pixel intervals. CLPOB sets the clamp level to 32 LSB (≈0.31 V) at the ADC output, while CLPDM enables dynamic offset correction. If both signals overlap, CLPOB takes precedence. This eliminates manual DC restoration and ensures consistent black level across temperature and exposure changes - a key requirement for the AD9804AJST in digital still camera applications.

What is the function of the RSTB pin on the AD9804AJST, and what timing is required?

The RSTB pin on the AD9804AJST is an active-low hardware reset that initializes internal registers, including the VGA gain register to its default value (0x096 = 6.0 dB). After power supplies stabilize, RSTB must be held low for ≥100 ns before returning high. Serial writes to the AD9804AJST must be delayed ≥20 µs after RSTB goes high to allow internal calibration. Failure to observe this timing risks incorrect gain settings or unstable CDS operation in the AD9804AJST.

Can the AD9804AJST operate from a single 3.0 V supply, or are separate analog/digital rails required?

The AD9804AJST can operate from a single 3.0 V supply connected to AVDD, DVDD, and DRVDD, as confirmed in the Power Supply Voltage specification (2.8 V to 3.6 V). However, using a separate 2.7 V DRVDD rail is recommended when interfacing with 2.7 V ASICs - it reduces digital switching noise coupling into analog sections and lowers overall power dissipation. All supplies must be independently decoupled per the AD9804AJST layout guidelines, regardless of whether rails are shared or split.

What is the purpose of the PBLK input on the AD9804AJST, and how does it interact with CLPOB/CLPDM?

The PBLK (Preblanking) input on the AD9804AJST forces all digital outputs (D0–D9) to zero during horizontal blanking intervals, simplifying downstream video timing alignment. PBLK is optional and does not affect clamping - CLPOB and CLPDM retain priority for black level control. If PBLK overlaps with CLPOB or CLPDM, the clamp functions remain active and unaffected. This behavior ensures reliable blanking without compromising black-level accuracy in the AD9804AJST.