CS4172

Features:

·Serial Input Bus
·2 MHz Operating Frequency
·Tangential Drive Algorithm
·80mA Drive Circuits
·0.5¡ Accuracy (Typ.)
·Power-On-Reset
·Protection Features Output Short Circuit Overtemperature


Specifications

Supply Voltage
VBB ...............................................................................................................................-1.0V to 15.0V
VCC ................................................................................................................................-1.0V to 6.0V
Digital Inputs .................................................................................................................-1.0V to 6.0V
Ground Potential Difference (|AGnd-DGnd|).................................................................................0.5V
Steady State Output Current ...............................................................................................±100mA
Forced Injection Current (Inputs and Supply).........................................................................±10mA
Operating Junction Temperature (TJ) .........................................................................................150
Storage Temperature Range .........................................................................................-65to 150
Lead Temperature Soldering Wave Solder (through hole styles only) ..........10 sec. max, 260peak
Reflow (SMD styles only) .........................................................60 sec. max above 183, 230 peak
ESD Susceptibility (Human Body Model).........................................................................................2kV


Description

The CS4172 is a monolithic BiCMOS integrated circuit used to translate a digital 10-bit word from a microprocessor/ microcontroller to complementary DC outputs. The DC outputs drive an air-core meter commonly used in vehicle instrument panels. The 10 bits of data are used to linearly control the quadrature coils of the meter directly with a 0.35¡ resolution and ±1.0¡ accuracy over the full 360¡ range of the gauge. The interface from the microcontroller is by a Serial Peripheral Interface (SPI) compatible serial connection using up to a 2MHz shift clock rate.

CS4172 digital code, which is directly proportional to the desired gauge pointer deflection, is shifted into a DAC and multiplexer. These two blocks provide a tangential conversion function to change the digital data into the appropriate DC coil voltage for the angle demanded. The tangential algorithm creates approximately 40% more torque in the meter movement than does a sin-cos algorithm at 45¡, 135¡,225¡, and 315¡ angles. This increased torque reduces the error due to pointer droop at these critical angles.

Each output buffer is capable of supplying up to 80mA per coil and are controlled by a common enable pin. When OE is low the output buffers are turned off but the logic portion of the chip remains powered and continues to operate normally. The Serial Gauge Driver CS4172 is self-protected against output short circuit conditions.

The output drivers CS4172 are disabled anytime the on-chip protection circuitry detects a short circuit condition. The outputs remain off until a falling edge is presented on CS. If the short circuit is still present the output drivers automatically disable themselves again. A thermal protection circuit limits the junction temperature to approximately 160¡C for conditions of high supply voltage and high ambient temperature.

The status pin (ST) reflects the state of the outputs and is low whenever the outputs are disabled.