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

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

Product Details

Key Features

Parametric specs for Display-Oriented ADCs
Resolution (±Counts) 20000
# Input Channels 1
Data Bus 7-Segment
Diff/S.E. Input Diff. Only
External VREF (V) (min) 0
External VREF (V) (max) 7
Bipolar VIN (±V) (max) 7
Package/Pins MQFP/44
PDIP/40
PLCC/44
Budgetary
Price (See Notes)
14.15
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Simplified Block Diagram

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Parameters

Parametric specs for Display-Oriented ADCs
Resolution (±Counts) 20000
# Input Channels 1
Data Bus 7-Segment
Diff/S.E. Input Diff. Only
External VREF (V) (min) 0
External VREF (V) (max) 7
Bipolar VIN (±V) (max) 7
Package/Pins MQFP/44
PDIP/40
PLCC/44
Budgetary
Price (See Notes)
14.15

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)

Applications/Uses

  • +3V Powered DMMs
  • +5V Powered Panel Meters
  • Digital Thermometers
  • Instruments
  • Portable Monitors
  • Weigh Scales

Description

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.

Simplified Block Diagram

MAX138, MAX139, MAX140: Typical Operating Circuit MAX138, MAX139, MAX140: Typical Operating Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .