Analog Devices Inc. AD9821KSTZRL7

Overview

AD9821KSTZRL7 from Analog Devices is a complete 12-bit, 40 MSPS imaging signal processor optimized for CMOS and CCD imagers with on-chip correlated double sampling (CDS). It integrates a differential sample-and-hold amplifier (SHA), 0 dB to 36 dB 10-bit VGA, optical black clamp, and 12-bit ADC - all operating from a single 3 V supply with 150 mW typical power consumption. It targets digital still cameras and industrial/scientific imaging systems requiring high-fidelity analog front-end conditioning.

For engineers reviewing the AD9821KSTZRL7 datasheet, AD9821KSTZRL7 pinout, AD9821KSTZRL7 application, or AD9821KSTZRL7 equivalent, key selection considerations include its 48-lead LQFP package, 12-bit straight-binary output coding, 40 MHz maximum DATACLK rate, and programmable black level clamp via 3-wire serial interface.

Technical Context

The AD9821KSTZRL7 implements a single-channel imager-mode signal chain: differential VIN+/VIN– inputs feed a SHA synchronized to DATACLK rising edges (3 ns aperture delay), followed by digitally controlled VGA with linear-in-dB gain curve (0.0351 dB/LSB), then optical black clamp using CLPOB-synchronized feedback to an 8-bit DAC, and finally a 12-bit ADC with 2.0 V full-scale range and ±0.5 LSB DNL.

Its internal register map supports independent configuration of VGA gain (1024-step resolution), clamp level (256-step resolution), power-down modes (standby: 5 mW; total power-down: 1 mW), and clock polarity. All registers are accessed via 3-wire serial interface (SCK ≤ 10 MHz, SL-latched update) with readback capability and simultaneous multi-register loading.

Key Specifications

Pinout & Package

AD9821KSTZRL7 is housed in a 48-lead LQFP (ST-48) package with 0.5 mm pitch, 7 mm × 7 mm body, and 1.4 mm max height per JEDEC MS-026BBC. Pin 1 identifier located at top-left corner; exposed paddle not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9821KSTZRL7, AD9822KSTZ offers higher resolution but increased power and cost, while TDA9886HN/C1 serves entirely different video standards and lacks raw sensor conditioning capability - making AD9821KSTZRL7 the optimal choice for 12-bit, low-power, CDS-equipped imager AFEs.

Availability

AD9821KSTZRL7 is available at Aetrix Electronics and suitable for digital still cameras, industrial machine vision systems, scientific imaging platforms, and medical endoscopy devices requiring stable component supply and long-term manufacturability.

Supply support for AD9821KSTZRL7 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 AD9821KSTZRL7 belongs to Analog Devices' Imaging Signal Processor product line, designed specifically to replace discrete analog front-ends in CMOS/CCD-based imaging systems requiring integrated gain, clamping, and digitization without external CDS circuitry.

FAQ

What is the maximum DATACLK frequency supported by the AD9821KSTZRL7?

The AD9821KSTZRL7 supports a maximum DATACLK frequency of 40 MHz, enabling real-time sampling of up to 40 million pixels per second. This rate is specified over the full operating temperature range (–20°C to +85°C) with AVDD = DVDD = 3.0 V. Exceeding this limit may cause timing violations in the SHA and ADC stages, resulting in missing codes or increased DNL error. The internal pipeline delay remains fixed at nine DATACLK cycles regardless of clock frequency.

Does the AD9821KSTZRL7 require external reference components?

No, the AD9821KSTZRL7 integrates an internal bandgap reference and does not require external reference ICs. However, it mandates external 0.1 µF ceramic decoupling capacitors on VRT (Pin 38) and VRB (Pin 39) connected directly to AVSS to stabilize the 2.0 V and 1.0 V reference rails. These capacitors are essential to achieve specified 12-bit linearity and ±0.5 LSB DNL performance - omitting them degrades ADC accuracy and increases noise susceptibility.

Can the AD9821KSTZRL7 interface directly with a 1.8 V digital ASIC?

Yes, the AD9821KSTZRL7 supports interfacing with 1.8 V digital ASICs via its dedicated DRVDD (Pin 13) and DRVSS (Pin 14) supply pins. These pins power only the D0–D11 digital output drivers and can be set to 1.8 V independently of DVDD (3.0 V), allowing level-matched communication without external level shifters. The datasheet confirms compatibility with 1.8 V logic thresholds when DRVDD = 1.8 V and load capacitance ≤20 pF - exceeding this capacitance requires series termination or buffering.

How is black level correction implemented in the AD9821KSTZRL7?

The AD9821KSTZRL7 implements optical black (OB) clamp correction using a closed-loop architecture triggered by the CLPOB input pulse during shielded pixel intervals. The ADC output is compared against a user-programmable 8-bit clamp level (0–255 LSB), and the error drives an internal DAC that injects correction current into the ADC input stage. This loop operates post-VGA, so its ±30 mV correction range is gain-dependent - at minimum VGA gain, correction extends to ±250 mV. Clamp level and enable/disable state are configured via the serial interface's Operation and Clamp Level registers.

What are the power-down modes available on the AD9821KSTZRL7?

The AD9821KSTZRL7 offers two hardware-configurable power-down modes accessed via the STBY pin (Pin 43): Standby mode (5 mW) retains register settings and reference bias while disabling the ADC and digital outputs; Total Power-Down mode (1 mW) shuts down all internal circuitry except the serial interface, requiring full reinitialization upon wake-up. Both modes are activated by driving STBY high; recovery times are 1 ms (Standby) and 3 ms (Total Power-Down) after STBY returns low, with internal reset completing before valid data output resumes.