Analog Devices Inc. ADV476KN80E

Overview

ADV476KN80E from Analog Devices is a monolithic CMOS RGB palette RAM-DAC designed for VGA and IBM Personal System/2 color graphics systems. It integrates a 256×18-bit color lookup table, triple 6-bit D/A converters, and asynchronous MPU interface, delivering RS-343A/RS-170–compliant analog outputs at up to 66 MHz pixel clock rate for high-resolution color display generation.

For engineers reviewing the ADV476KN80E datasheet, ADV476KN80E pinout, ADV476KN80E application, or ADV476KN80E equivalent, this device supports real-time palette updates during vertical blanking, pixel-level masking for animation overlays, and direct coaxial cable drive without external buffers - critical for legacy graphics controller design and retro-computing video subsystems.

Technical Context

The ADV476KN80E implements a pipelined 66 MHz architecture with independent pixel clock (PCLK) and MPU bus domains. Its 256-entry × 18-bit palette RAM stores three 6-bit RGB components per address, accessed via P0–P7 pixel select inputs or MPU-controlled RS0/RS1 command decoding.

Each of the three current-output DACs delivers up to 19.05 mA into 37.5 Ω (doubly terminated 75 Ω), with guaranteed monotonicity and ±0.5 LSB integral nonlinearity. The BLANK input latches on PCLK's rising edge to force all outputs to black level, enabling precise sync timing in raster-scan CRT systems.

Key Specifications

Pinout & Package

ADV476KN80E is packaged in a 28-pin plastic DIP (N-28), 0.6" wide, with dual analog/digital power and ground pins optimized for noise isolation in mixed-signal video applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RGB palette DAC applications.

Compared with ADV476KN80E, the ADV478KP66 offers expanded reference configuration options at the cost of larger footprint and layout complexity, while the INMOS 176-066 provides mechanical compatibility but lacks modern DAC performance guarantees and power efficiency.

Availability

ADV476KN80E is available at Aetrix Electronics and suitable for high-resolution color graphics, CAE/CAD/CAM systems, and legacy instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for ADV476KN80E 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies.

The ADV476KN80E belongs to Analog Devices' legacy video interface product line, engineered specifically for VGA and IBM PS/2 color graphics subsystems requiring integrated palette RAM and triple DAC functionality in compact monolithic form.

FAQ

What is the maximum supported pixel clock frequency for the ADV476KN80E?

The ADV476KN80E is rated for 66 MHz pipelined operation, matching the highest speed grade in the ADV476 family. This enables support for resolutions such as 1024×768 at 85 Hz refresh or 1280×1024 at 72 Hz under standard VGA timing constraints. The device maintains guaranteed timing margins (e.g., t12 = 15.3 ns min setup) and full-spec performance including ±0.5 LSB linearity and 75 pV·sec glitch impulse at this rate. ADV476KN80E operates reliably across 0°C to +70°C ambient temperature with proper decoupling and layout per Analog Devices' PCB guidelines.

Does the ADV476KN80E support both current-mode and voltage-mode reference inputs?

No - the ADV476KN80E supports current-mode reference only via the IREF pin, requiring an external current source (e.g., LM334) set to 8.88 mA for RS-343A compliance. Voltage-reference operation is not supported on this 28-pin DIP variant. That capability is exclusive to the 44-pin PLCC versions (e.g., ADV476KP66 and ADV478KP66), which include dedicated VREF and COMP pins. ADV476KN80E's IREF input accepts –3 mA to –10 mA, with full-scale output voltage determined by VO = 2.15 × IREF × RL.

How does the pixel read mask register function in the ADV476KN80E?

The pixel read mask register performs bitwise logical AND between incoming P0–P7 pixel data and an 8-bit mask value loaded via the MPU interface. This enables dynamic color plane reduction - for example, masking upper bits to create animated overlays or flashing UI elements without modifying the main palette RAM. The mask register is accessible at RS0=1, RS1=0 and operates transparently during active video; ADV476KN80E applies it synchronously with PCLK, ensuring pixel-accurate timing. Its use eliminates CPU overhead associated with palette reloading during screen updates.

Can the ADV476KN80E drive standard 75 Ω coaxial video cables directly?

Yes - the ADV476KN80E's RED, GREEN, and BLUE outputs are high-impedance current sources capable of directly driving doubly terminated 75 Ω coaxial cables (i.e., 37.5 Ω source termination). When loaded with 37.5 Ω, each channel delivers 0.714 V peak-to-peak for RS-343A compliance or 1.0 V for RS-170, with typical output current of 19.05 mA at full scale. No external buffers or amplifiers are required, reducing system component count and signal path distortion. ADV476KN80E maintains <75 pV·sec glitch impulse and –35 dB clock feedthrough under these conditions.

What MPU bus protocols and timing modes does the ADV476KN80E support?

The ADV476KN80E supports asynchronous 8-bit MPU access using standard RD/WR strobes and RS0/RS1 command encoding. It implements four distinct operations: address register write/read (RS1=0,RS0=0 or RS1=1,RS0=1), palette RAM access (RS1=0,RS0=1), and pixel read mask register access (RS1=1,RS0=0). All timing parameters - including t4 (RD to data valid, 40 ns max), t6 (RD negated to high-Z, 10 ns min), and t8 (WR pulse width, 50 ns min) - are fully specified for 66 MHz operation. ADV476KN80E requires no wait states and operates independently of PCLK, enabling palette updates during vertical blanking without disrupting video output.