The MAX138/MAX139 are 3 ½ digit A/D converters (ADCs) with on-board LCD (MAX138) and LED (MAX139) display drivers. The MAX138/MAX139 also contain a charge-pump voltage inverter. The charge-pump inverter allows the MAX138/MAX139 to measure both positive and negative input voltages while operating from a single power-supply voltage from +2.5V to +7V. The operating circuits of the MAX138/MAX139 are similar to those of the ICL7136 and ICL7137 respectively, except the MAX138/MAX139 have an internal oscillator and an external charge-pump capacitor connected to pins 38 and 40. MAX140 is a low segment-current version of the MAX139 intended for use with low-current LED displays. Applications * +3V Powered DMMs * +5V Powered Panel Meters * Digital Thermometers * Instruments * Portable Monitors * Weigh Scales * Single Supply +2.5V to +7.0V Operation* Measures Both Positive and Negative Input Voltages* Charge-Pump Voltage Inverter Generates a Negative Supply Voltage* Internal Bandgap Reference* On-Board Display Driver* Low Segment Current (MAX140)