Analog Devices Inc. ADV476KN50E

Overview

ADV476KN50E from Analog Devices is a monolithic 6-bit RGB video RAM-DAC with 256×18 color palette, 50 MHz pixel clock support, RS-343A/RS-170 analog outputs, and MPU-compatible 8-bit bidirectional data interface - used in VGA/PS/2 graphics systems for real-time color lookup and analog video generation.

For engineers reviewing the ADV476KN50E datasheet, ADV476KN50E pinout, ADV476KN50E application, or ADV476KN50E equivalent, this page delivers verified timing specs (t12 = 20 ns), DAC monotonicity (±0.5 LSB INL), blank-level accuracy (±0.5 LSB), IREF range (–3 to –10 mA), and DIP-28 package mapping - all confirmed from Analog Devices REV. B datasheet.

Technical Context

The ADV476KN50E integrates a 256-entry × 18-bit color palette RAM, triple 6-bit current-output DACs, and asynchronous MPU bus interface with RS0/RS1 command decoding. It supports pixel-synchronous RGB output via PCLK-latched P0–P7 address inputs and BLANK control, enabling real-time palette updates during vertical/horizontal retrace.

Its analog outputs (RED/GREEN/BLUE) are high-impedance current sources (21 mA max, 1.5 V min into 37.5 Ω), directly compatible with doubly terminated 75 Ω coaxial loads per RS-343A. The device uses +5 V CMOS process, operates from 0°C to +70°C, and achieves guaranteed monotonicity with ±0.5 LSB integral nonlinearity.

Key Specifications

Pinout & Package

ADV476KN50E is packaged in a 28-pin plastic DIP (N-28), 0.6" wide, with dual-purpose pins supporting both MPU and pixel clock domains. Pin functions are electrically isolated between digital control (RD/WR/RS0/RS1/D0–D7) and video timing (PCLK/P0–P7/BLANK) paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADV476KN50E, the ADV476KN66 offers higher bandwidth headroom while maintaining full compatibility, whereas the ADV476KP50 trades DIP convenience for PLCC flexibility and alternate reference options - both preserve identical palette architecture, MPU interface, and video timing behavior.

Availability

ADV476KN50E is available at Aetrix Electronics and suitable for high-resolution color graphics, CAE/CAD/CAM systems, and desktop publishing applications requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for ADV476KN50E 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 semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies.

The ADV476 product line was designed specifically for VGA and IBM Personal System/2 color graphics subsystems, delivering integrated palette RAM and triple DAC functionality in monolithic CMOS for plug-in replacement of discrete solutions.

FAQ

What is the maximum pixel clock frequency supported by the ADV476KN50E?

The ADV476KN50E supports a maximum pixel clock frequency of 50 MHz, as specified in the Ordering Guide and confirmed by timing parameter t12 = 20 ns minimum clock cycle time. This enables operation in standard VGA and PS/2 graphics modes up to 1024×768 resolution at 60 Hz refresh rate. Exceeding 50 MHz may violate setup/hold timing margins and cause pixel data mislatching. The ADV476KN50E datasheet explicitly lists 50 MHz as its speed grade, distinct from the 35 MHz and 66 MHz variants.

Does the ADV476KN50E require an external current reference or can it use a voltage reference?

ADV476KN50E requires an external current reference connected to the IREF pin, sinking –3 to –10 mA to set full-scale DAC output voltage. It does not support direct voltage reference configuration; that capability is exclusive to the PLCC-packaged variants (e.g., ADV476KPxx) which include dedicated VREF and COMP pins. Using a voltage source on IREF of the ADV476KN50E will result in incorrect output scaling and potential damage due to reverse current flow.

How does the pixel read mask register function in the ADV476KN50E?

The pixel read mask register in ADV476KN50E performs bitwise logical AND between incoming P0–P7 pixel address lines and an 8-bit mask value loaded via the MPU interface. This dynamically partitions the 256-color palette into user-defined subspaces - for example, masking upper bits enables animation overlays without altering frame buffer or palette RAM contents. The mask register is accessed using RS0=1, RS1=0 and is fully compatible with the standard MPU timing protocol defined in Table III of the datasheet.

Is the ADV476KN50E pin-compatible with the INMOS 171/176 series?

Yes, the ADV476KN50E is explicitly designed as a plug-in replacement for INMOS 171/176, with identical pinout, register map, and electrical interface characteristics. The datasheet states "Plug-in Replacement for INMOS 171/176" under FEATURES and confirms pin and software compatibility in the GENERAL DESCRIPTION. This includes matching DIP-28 footprint, TTL-compatible signaling levels, and identical MPU bus timing requirements.

What analog output termination is required for RS-343A compliance with the ADV476KN50E?

For RS-343A compliance, ADV476KN50E requires doubly terminated 75 Ω coaxial cable loads, implemented as 37.5 Ω source termination per RGB channel (Figure 4a). With IREF = –8.88 mA, this yields 0.714 Vpp output across 75 Ω - matching RS-343A black-to-white swing. Single-termination (75 Ω to ground) is insufficient and produces incorrect amplitude; the datasheet specifies RL = 37.5 Ω for RS-343A and mandates source termination placement near the ADV476KN50E die.