3¾ Digit DMM Circuit

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The MAX133 and MAX134 are integrating A/D converters for 3¾ digit multimeters and data acquisition systems such as data loggers and weigh scales. The A/D's internal resolution is ±40,000 counts. An extra digit is supplied as a guard digit to allow autozero or tare of a 4000 count displayed reading to 1/10 of a displayed count. The conversion time is 50ms.

The MAX133 and MAX134 differ only in their microprocessor interface. The MAX133 has a 4 bit multiplexed address/data bus while the MAX134 has 3 separate address lines and a 4 bit bidirectional data bus. Both devices can be used with 4, 8, and 16 bit microprocessors.

When controlled by a microprocessor, the MAX133 and MAX134 can perform auto-ranging measurements from ±400.0mV to ±4000V full scale. External attenuator resistors are required, but range switching is performed by the A/D.

The power supply is typically a 9V battery or ±5V. Operating current is typically 100µA while standby current is only 25µA.
MAX133, MAX134: Pin Configuration MAX133, MAX134: Pin Configuration Enlarge+

Key Features

  • 40,000 Count Resolution
  • 0.025% Accuracy
  • 20 Conversions per Second
  • Microprocessor Interface
  • 100µA Operating Supply Current
  • Low External Component Count
  • 5µV Resolution
  • Demonstration Kit Available MAX134/DEMO


  • Data Acquisition Systems
  • Data Loggers
  • Digital Panel Meters
  • Weigh Scales

See parametric specs for Display-Oriented ADCs (27)

Part NumberResolution
Conv. Rate
Data BusDiff/S.E. InputExternal VREF
External VREF
Unipolar VIN
(max)(min)(max)(max)(See Notes)
MAX133 40000.02µP/4Diff. Only0660.216
$15.64 @1k

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.

MAX134EVKIT: Evaluation Kit for the MAX134
Request Reliability Report for: MAX134 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

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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