Low Power, 31⁄2 Digit A/D Converter with Display Hold

Description

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The MAX136 is a monolithic analog-to-digital converter (ADC) with very high input impedance. It differs from the Maxim ICL7136 in that the MAX136 provides a Hold pin, which makes it possible to hold or "freeze" a reading. The MAX136 directly drives a nonmultiplexed liquid crystal (LCD) display, requiring no external drive circuitry. With minor external component changes, it is pin compatible with the ICL7116 but with significantly reduced power consumption, making the MAX136 a superior device for portable systems.

Versatility and accuracy are inherent features of this ADC. The dual-slope conversion technique automatically rejects interference signals common in industrial environments. True differential inputs allow direct measurements of bridge transducer outputs or load cells. The zero-integrator phase eliminates overrange hangover and hysteresis effects. The MAX136 offers high accuracy by lowering rollover error to less than one count and zero reading drift to less than 1µV/°C.

Key Features

• Power Dissipation Guaranteed Less than 1mW–9V Battery Life 3000 Hours Typical
• Hold Pin Allows Indefinite Display Hold
• Guaranteed First Reading Recovery from Overrange
• On-Board Display Drive Capability—No External Circuitry Required
• High-Impedance CMOS Differential Inputs
• Low Noise (< 15µV_P-P) Without Hysteresis or Overrange Hangover
• Clock and Reference On-Chip
• Zero Input Gives Zero Reading
• True Polarity Indication for Precision Null Applications
• Key Parameters Guaranteed Over Temperature

Applications/Uses

• Conductance
• Current
• Material Thickness
• Pressure
• Resistance
• Speed
• Temperature
• Voltage