GENERAL DESCRIPTION
The ALD500AU/ALD500A/ALD500 are integrating dual slope analog processors, designed to operate on ±5V power supplies for building precision analog-to-digital converters. The ALD500AU/ALD500A/ALD500 feature specifications suitable for 18 bit/17 bit/16 bit resolution conversion, respectively. Together with three capacitors, one resistor, a precision voltage reference, and a digital controller, a precision Analog to Digital converter with auto zero can be implemented. The digital controller can be implemented by an external microcontroller, under either hardware (fixed logic) or software control. For ultra high resolution applications, up to 23 bit conversion can be implemented with an appropriate digital controller and software.

FEATURES
• Resolution up to 18 bits plus sign bit and over-range bit
• Accuracy independent of input source impedances
• High input impedance of 1012 Ω
• Inherently filters and integrates any external noise spikes
• Differential analog input
• Wide bipolar analog input voltage range ±3.5V
• Automatic zero offset compensation
• Low linearity error - as low as 0.002%
• Fast zero-crossing comparator - 1µs
• Low power dissipation - 6mW typical
• Automatic internal polarity detection
• Low input current - 2pA typical
• Microprocessor controlled conversion
• Optional digital control from a microcontroller, an ASIC, or a dedicated digital circuit
• Flexible conversion speed versus resolution trade-off

APPLICATIONS
• 4 1/2 digits to 5 1/2 digits plus sign measurements
• Precision analog signal processor
• Precision sensor interface
• High accuracy DC measurement functions
• Portable battery operated instruments
• Computer peripheral
• PCMCIA