Diodes Incorporated ZMT31TC

Overview

ZMT31TC from Zetex Semiconductors is a contactless angular position sensor IC based on dual Wheatstone bridge architecture for measuring rotation angle and direction of a rotating permanent magnet. It delivers sinusoidal differential output voltages proportional to sin²(θ) and sin²(θ+45°), operates at 5 V supply, supports -25°C to +130°C ambient, and is packaged in SM-8 for water meter and automotive pedal position sensing.

For engineers reviewing the ZMT31TC datasheet, ZMT31TC pinout, ZMT31TC application, or ZMT31TC equivalent, this device enables high-accuracy magnetic angular measurement without mechanical wear-critical for sealed rotary encoders, non-contact potentiometers, and safety-critical pedal position feedback in automotive systems.

Technical Context

The ZMT31TC integrates two matched Wheatstone bridges oriented at 45° relative to each other on a single die, enabling quadrature-based angle resolution via analog voltage comparison. Its bridge resistance (2.0–4.0 kΩ) and offset voltage (<±2 mV/V) are trimmed for precision, with sensitivity of 0.2 (mV/V)/° under defined field alignment.

Output signals are ratiometric to supply voltage (VB = 5 V), supporting robust operation across temperature (TCOFF ≤ ±3 μV/V·K). The sensor requires no external signal conditioning for basic direction/counting, though full angle reconstruction demands analog front-end processing of both bridge outputs.

Key Specifications

Pinout & Package

Package: SM-8 (12 mm tape, 4000 units/reel), 6.3–6.7 mm × 3.3–3.7 mm footprint, 1.7 mm max height, 15° lead chamfer.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar magnetic angular sensing applications.

Compared with ZMT31TC, AS5055-BSOT reduces system BOM by integrating conversion but increases firmware overhead, while TLE5012B E1000 adds safety features and absolute range at higher cost and complexity-ZMT31TC remains optimal for analog-native, cost-sensitive, directional-counting applications.

Availability

ZMT31TC is available at Aetrix Electronics and suitable for water metering, automotive pedal position sensing, and industrial rotary switch designs requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for ZMT31TC includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Zetex Semiconductors (now part of Diodes Incorporated) specialized in high-performance analog and mixed-signal ICs for industrial and automotive sensing, with emphasis on magnetic, thermal, and precision signal conditioning.

The ZMT series was developed specifically for contactless angular and rotational measurement in harsh environments-targeting metering, pedal sensing, and sealed rotary controls where reliability and analog simplicity are critical.

FAQ

What is the minimum magnetic field strength required for reliable operation of ZMT31TC?

The ZMT31TC requires a rotating magnetic field with flux density >50 kA/m (≈6.3 mT) parallel to the chip surface. This corresponds to typical N35–N42 grade neodymium magnets sized ≥3 mm diameter at ≤3 mm air gap. Field strength below this threshold causes reduced output amplitude and increased angle quantization error.

Can ZMT31TC be used with a single-ended ADC instead of differential input?

Yes, but with reduced accuracy. Each bridge's output (e.g., pins 1 & 5) is centered near VB/2, so single-ended sampling is possible using an ADC reference tied to VB/2. However, common-mode rejection is lost, increasing susceptibility to supply ripple and PCB noise-differential acquisition is strongly recommended for <1° angle error.

Does ZMT31TC provide absolute or incremental angle measurement?

ZMT31TC provides analog incremental angle data via two phase-shifted sine-wave outputs. It does not compute absolute angle internally. Full 360° absolute position requires external processing (e.g., arctangent calculation on digitized bridge pairs) or interpolation between zero-crossings-no onboard encoder logic or memory is present.

Is external trimming or calibration required for production use?

Factory-trimmed offset and symmetry minimize initial error, but system-level calibration is recommended. A one-point zero-angle trim (at known magnet orientation) corrects residual offset; gain matching between bridges improves quadrature fidelity. No laser trimming or EEPROM is needed-calibration coefficients can be stored in host MCU flash.