Inductance-to-digital converter copes with harsh environments

2nd September 2015

Mick Elliott

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Datasheet

An inductance-to-digital converter (LDC) from Texas Instruments (TI) is a 1.8V to 3.3V, high-resolution data converter designed for short-range, high-speed, contactless sensing of position, rotation, or motion. The LDC1101 provides accurate measurements in both controlled and harsh environments, making it ideal for auotomotive consumer, industrial computer, and communications applications.

The converter features dual inductive measurement cores, allowing for 16-bit resonator resistance (R_P) and inductance (L) measurements at more than 150 Ksps. Simultaneously, it can perform 24-bit-resolution inductance measurements at more than 180ksps.

The device includes a threshold-compare function which can be dynamically updated while the device is running, greatly simplifying designs such as high-speed gear counting.

It supports a wide range of inductor/capacitor (LC) combinations with oscillation frequencies ranging from 500kHz to 10MHz and R_P ranging from 1.25 kΩ to 90 kΩ. The device is configured and conversion results retrieved through a simple 4-wire SPI.

The only external components necessary for operation are a 15nF capacitor for internal LDO bypassing and supply bypassing for V_DD.

TI’s LDC1101EVM evaluation module, also available from Mouser Electronics, allows designers to test and demonstrate inductive sensing technology using the LDC1101 device.

The evaluation board includes an example PCB sensor coil that connects to the LDC1101. Designers can use the onboard TI MSP430 microcontroller to interface the LDC to a host computer. This module is designed to provide the user with maximum flexibility for system prototyping.