ADV476KN40

Digital To Analog Converters Overview

The ADV476KN40 is a CMOS monolithic RAM-DAC designed for VGA and Personal System/2 color graphics. It integrates a 256x18 color palette lookup table, pixel mask register, and triple 6-bit video D/A converters. The device supports pipelined operation at clock rates of 35 MHz, 50 MHz, or 66 MHz, enabling simultaneous display of up to 256 colors from a 262,144-color palette. It features RS-343A/RS-170 compatible analog outputs without external buffering. Key electrical parameters include a supply voltage (VCC) range of 4.5 V to 5.5 V, maximum supply current of 220 mA at 66 MHz, and integral nonlinearity guaranteed to ±0.5 LSB max. The component operates within an ambient temperature range of 0°C to +70°C.

Digital To Analog Converters Feature Summary

• Pin-compatible and software-compatible with INMOS 171/176 devices.
• Contains a 256x18 color palette RAM and asynchronous MPU interface for direct access to the lookup table.
• Triple 6-bit DACs provide RGB outputs capable of driving doubly terminated 75 Ω coaxial cables directly.
• Pixel read mask register allows alteration of displayed colors via bitwise logical ANDing without updating the RAM.

Digital To Analog Converters Applications

• High resolution color graphics systems
• CAE/CAD/CAM applications
• Image processing instrumentation
• Desktop publishing equipment

Digital To Analog Converters Procurement Notes

This component is classified as obsolete by Analog Devices. Verification of availability requires checking distributor stock status, as new production is discontinued. Buyers should confirm the specific speed grade suffix (e.g., KN35, KN50, KN66) matches system requirements, as the base model number does not specify the clock rate. Replacement considerations involve evaluating modern RAM-DACs or FPGA-based solutions due to the end-of-life status.

Digital To Analog Converters Selection Notes

Select the appropriate speed variant based on the system clock: ADV476KN35 for 35 MHz, ADV476KN50 for 50 MHz, or ADV476KN66 for 66 MHz. The 'KN' suffix indicates a 28-pin plastic DIP package. Ensure the design accommodates the required reference current (typically 8.88 mA for RS-343A levels into a 37.5 Ω load). Verify that the PCB layout adheres to the recommended separation of analog and digital power planes to maintain signal integrity at high clock frequencies.

Digital To Analog Converters Part Context

The ADV476 series was designed as a drop-in replacement for legacy INMOS video DACs in VGA and PS/2 graphics adapters. It represents a CMOS implementation of color palette RAM-DAC technology, offering lower power dissipation compared to earlier bipolar counterparts. The device was widely used in early PC graphics cards and specialized video instrumentation before being superseded by higher-resolution and integrated graphics controllers.

Digital To Analog Converters Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. As the ADV476 is obsolete, designers must evaluate alternative components such as the ADV471 or ADV478 series, or implement functionality using programmable logic devices (FPGAs) and modern RAM-DACs. Pin compatibility with INMOS 171/176 may simplify mechanical integration but requires functional verification.