ICL7135CMH+D

ADCs/DACs - Special Purpose Overview

The ICL7135CMH+D 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 zero reading drift of 0.5µV/°C, input bias current of 10pA maximum, and noise of 15µV peak-to-peak. It operates on single or dual supplies ranging from +4V to +6V and -3V to -8V, consuming approximately 3mA total supply current at 120kHz clock frequency.

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, and UNDERRANGE signals for microprocessor interfacing.
• High-precision analog performance including 10µV auto-zero accuracy and 10pA maximum input bias current.
• True differential input 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 high linearity and low drift

ADCs/DACs - Special Purpose Procurement Notes

Verify the specific suffix CMH+D corresponds to the 44-MQFP package as indicated in distributor listings, while confirming functional compatibility with the standard 28-pin datasheet specifications. Ensure the source document explicitly supports the lead-free status associated with the '+' suffix. Cross-reference the manufacturer's ordering information to confirm availability and exact pinout mapping for this package variant.

ADCs/DACs - Special Purpose Selection Notes

Select external components based on the required reading rate and power line rejection needs. Use polypropylene or Teflon integrating capacitors to minimize dielectric absorption errors. Set the clock frequency to 120kHz for 3 readings per second or 100kHz for 2.5 readings per second to optimize normal mode rejection against 50Hz/60Hz interference. Ensure the reference voltage stability matches the desired absolute measurement accuracy.

ADCs/DACs - Special Purpose Part Context

The ICL7135 series represents a family of high-precision integrating ADCs originally developed by Maxim Integrated. The ICL7135CMH+D is a specific package variant of this core component, maintaining the same internal circuitry and electrical characteristics as other packages in the ICL7135 family. It serves as a direct replacement for legacy parts in existing designs requiring multiplexed BCD output capabilities.

ADCs/DACs - Special Purpose Replacement Considerations

Direct pin-compatible replacements within the same package are limited due to the unique 44-pin MQFP form factor not being standard across the entire ICL7135 family which typically uses 28-pin packages. Verify if the application can accommodate the pin count difference or if a breakout solution is required. Check for updated equivalents from Analog Devices that may offer improved ESD protection or temperature ranges.