ICL7135CQI+

ADCs/DACs - Special Purpose Overview

The ICL7135CQI+ is a monolithic 4½-digit analog-to-digital converter manufactured by Analog Devices/Maxim Integrated. It utilizes dual-slope integration to achieve ±20,000 count resolution with guaranteed ±1 count accuracy and a 2.0000V full-scale capability. The device features high-impedance differential inputs, true ratiometric operation, auto-zero, and auto-polarity functions. Key electrical parameters include a maximum input bias current of 10pA, zero 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 and is housed in a 28-pin plastic chip carrier package.

ADCs/DACs - Special Purpose Feature Summary

• Dual-slope conversion architecture providing ±20,000 count resolution and ±1 count accuracy.
• Multiplexed BCD outputs with STROBE, BUSY, OVERRANGE, UNDERRANGE, and POLARITY status lines for microprocessor interfacing.
• High-precision analog performance including 10pA max input bias current and <1 count rollover error.
• True differential inputs ensuring zero reading for 0V input and precise null detection.

ADCs/DACs - Special Purpose Applications

• Microprocessor-based data acquisition and control systems
• Precision digital voltmeters (DVM) and panel meters (DPM)
• Industrial measurement instruments requiring low noise and high linearity

ADCs/DACs - Special Purpose Procurement Notes

Verify the specific ordering suffix CQI+ corresponds to the 28-lead plastic chip carrier package when sourcing. Confirm that the component meets the required operating temperature range of 0°C to +70°C for the intended application environment. Ensure compatibility with standard ±5V power supplies and check for availability from authorized distributors as stock levels may vary.

ADCs/DACs - Special Purpose Selection Notes

Select this component for applications requiring high precision and direct multiplexed BCD output without external decoding logic. Ensure the integrating capacitor selected has low dielectric absorption, such as polypropylene or Teflon, to maintain integral linearity. Verify that the clock frequency supports the desired conversion rate while maintaining normal mode rejection against power line interference.

ADCs/DACs - Special Purpose Part Context

The ICL7135 series represents a family of high-precision A/D converters designed for electronic instrumentation. The ICL7135CQI+ variant specifically denotes the plastic chip carrier package option within this lineup. It serves as a second-source equivalent to earlier Intersil designs, offering improved ESD protection and tighter test specifications while maintaining functional compatibility with standard dual-slope ADC circuits.

ADCs/DACs - Special Purpose Replacement Considerations

Direct pin-compatible replacements include other variants in the ICL7135 family such as ICL7135CPI (Plastic DIP) or ICL7135CJI (Lead CERDIP), provided the package form factor matches the PCB footprint. Cross-referencing with Maxim Advantage™ qualified parts ensures identical functionality with potentially enhanced reliability parameters.