3 1/2 Digit ADC with Reference, Charge Pump, and Direct LED Drivers

Operates with Single +2.5V to +7V Supply, Accepts Bipolar Inputs

Please check latest availability status for a specific part variant.


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.
MAX138, MAX139, MAX140: Typical Operating Circuit MAX138, MAX139, MAX140: Typical Operating Circuit Enlarge+

Key Features

  • 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)


  • +3V Powered DMMs
  • +5V Powered Panel Meters
  • Digital Thermometers
  • Instruments
  • Portable Monitors
  • Weigh Scales
Part NumberResolution
Data BusDiff/S.E. InputExternal VREF
External VREF
Bipolar VIN
minmaxmaxSee Notes
MAX138 20007-SegmentDiff. Only077
$9.93 @1k
MAX139 20000
$12.71 @1k
MAX140 2000
$9.93 @1k
See All Display-Oriented ADCs (28)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Technical Documents

Tutorial 2102 Delta-Sigma ADCs Replace Integrating ADCs for Panel Meters

Quality and Environmental Data

Request Reliability Report for: MAX138 
Lead-Free Package Tin (Sn) Whisker Reports

CAD Symbols and Footprints

  • MAX138CMH+C10166
  • MAX138CMH+D
  • MAX138CMH+TD
  • MAX138CPL+
  • MAX138CQH+D
  • MAX138CQH+TD
  • MAX138EQH+D
  • Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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    Related Resources

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