ICL7135CPI

ADCs/DACs - Special Purpose Overview

The ICL7135CPI is a monolithic 4½ digit analog-to-digital converter featuring dual-slope conversion architecture. It provides ±20,000 count resolution with guaranteed ±1 count accuracy and a 2.0000V full-scale capability. The device utilizes true differential inputs with high impedance and ratiometric operation. Key electrical parameters include a maximum input bias current of 10pA, zero reading drift of 0.5µV/°C, and supply currents of 3.0mA max for both +5V and -5V rails at 70°C. It operates within a temperature range of 0°C to +70°C in a 28-pin Plastic DIP package.

ADCs/DACs - Special Purpose Feature Summary

• Dual-slope A/D conversion with ±1 Count accuracy over the full temperature range
• Multiplexed BCD outputs compatible with TTL logic levels
• Auto-zero and auto-polarity functions ensuring high precision
• Status outputs for Over-range, Under-range, BUSY, STROBE, and Polarity

ADCs/DACs - Special Purpose Applications

• Microprocessor-based data acquisition systems
• Precision Digital Voltmeters (DVMs)
• Digital Panel Meters (DPMs)
• Industrial process control instrumentation

ADCs/DACs - Special Purpose Procurement Notes

Verify the specific suffix 'CPI' corresponds to the 28-lead Plastic DIP package and the 0°C to +70°C commercial temperature range. Confirm that the source document explicitly lists this part number as available from Analog Devices or Maxim Integrated distributors. Check for RoHS compliance status if required by the application specifications.

ADCs/DACs - Special Purpose Selection Notes

Select external components based on the integrating resistor formula to maintain buffer output current between 5µA and 40µA. Use polypropylene or Teflon capacitors for the integrator to minimize dielectric absorption errors. Ensure the clock frequency is an integer multiple of the power line frequency (e.g., 120kHz for 60Hz rejection) to maximize normal mode rejection capabilities.

ADCs/DACs - Special Purpose Part Context

The ICL7135 is part of the Maxim Integrated family of 4½ digit A/D converters. It serves as a direct replacement for earlier Intersil designs while offering improved ESD protection and tighter test specifications under the Maxim Advantage program. The device integrates the analog front-end and digital control logic required for high-precision DC voltage measurements.

ADCs/DACs - Special Purpose Replacement Considerations

The ICL7135CPI is functionally equivalent to the ICL7135CJI (Lead CERDIP) and ICL7135CQI (Lead Plastic chip carrier). These variants share identical pinouts and electrical characteristics, differing only in the physical package material.