Triple Air-Core Gauge Driver
The company's new triple air-core gauge driver provides precise controlling of vehicle instrument panels that includes speedometers, tachometers, fuel gauges and temperature meters.
Complete with serial-to-parallel input bus interface for seamless microprocessor to air-core control, the CS4122 translates a 12-bit digital word provided by a microcontroller into addressable DC outputs that control three air-core meters (one 360 degree major gauge and two 112 degree minor gauges).
Equipped with an on-chip Serial Peripheral Interface (SPI) port, the CS4122 employs a 2 MHz clock frequency to shift input data to the appropriate Digital-to-Analog Converter (DAC) (digital-to-analog converter)/multiplexer (MUX) channel. The DAC/MUX provides an accurate tangential conversion to a DC coil voltage representing the digital data, and on-chip output buffer amplifiers deliver 70 mA of drive current to each quadrature coil. Other features that make the CS4122 unique are a power-on reset, thermal shutdown and self-protection against output short-circuit conditions.
Independently addressable gauges allow the two minor gauges to be addressed separately from the major gauge by means of a bias pin. The chip guarantees ± 0.75 degree accuracy and resolution to within 0.35 degrees over its major 360 degree gauge, and 0.44 degree resolution and ± 1 percent accuracy over both minor 112 degree gauges. The key to the CS4122's high resolution and accuracy is its use of a tangential conversion algorithm that converts digital input data from the processor into angle information required to drive the coils of the gauge. A tangential algorithm creates approximately 40 percent higher peak torque in the meter movement than a conventional sine-cosine algorithm. The increased torque reduces the error due to pointer droop at critical angles of 45 degrees, 135 degrees, 225 degrees and 315 degrees.
The CS4122 is available in an individual 24-lead SOIC package. The device operates from two DC supply voltages: the V (logic supply), with a maximum input voltage of 6V, and the V (output driver supply), with a maximum input voltage of 15V.