Features: • Resolution up to 18 bits plus sign bit and over-range bit
• Accuracy independent of input source impedances
• Accurate on-chip voltage reference
• Tempco as low as 10 ppm/°C guaranteed
• Chip select - power down mode
• High input impedance of 1012 W
• 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 0.001% typical
• Fast zero-crossing comparator - 1ms
• Low power dissipation - 6mW typical
• Automatic internal polarity detection
• Low input current - 2pA typical
• Optional digital control from a microcontroller, an ASIC, ora dedicated digital circuit
• Flexible conversion speed vs. resolution trade-offApplication• 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
• PCMCIAPinout
SpecificationsSupply voltage, V+ 13.2V
Differential input voltage range -0.3V to V+ +0.3V
Power dissipation 600 mW
Operating temperature range PE, SE package 0°C to +70°C
Operating temperature range QE package -55°C to +125°C
Storage temperature range -65°C to +150°C
Lead temperature, 10 seconds +260°CDescriptionThe ALD500RAU/ALD500RA/ALD500R are integrating
dual slope analog processors, designed to operate on ±5V
power supplies for building precision analog-to-digital converters. The ALD500RAU/ALD500RA/ALD500R feature specifications suitable for 18 bit/17 bit/16 bit
resolution conversion, respectively. Together with three capacitors, two resistors, 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.
The ALD500RAU/ALD500RA/ALD500R analog processors accept differential inputs and the external digital controller first counts the number of pulses at a fixed clock rate that a capacitor requires to integrate against an unknown analog input voltage, then counts the number of pulses required to deintegrate the capacitor against a known internal reference voltage. This unknown analog voltage can then be converted by the microcontroller to a digital word, which is translated into a high resolution number, representing an accurate reading. This reading, when ratioed against the reference voltage, yields an accurate, absolute voltage measurement reading.
The ALD500RAU/ALD500RA/ALD500R analog processors consist of on-chip digital control circuitry to accept control inputs, integrating buffer amplifiers, analog switches, and voltage comparators and a highly accurate, ultra-stable voltage reference. It functions in four operating modes, or phases, namely auto zero, integrate, deintegrate, and integrator zero phases. At the end of a conversion, the comparator output goes from high to low when the integrator crosses zero during deintegration. ALD500RAU/ALD500RA/ALD500R analog processors also provide direct logic interface to CMOS logic families.
ALD500RA Data Sheet
