Abstract

The TPS7B4255-Q1 and TPS7B4256-Q1 are low drop-out, tracking, linear regulators designed for use in automotive applications to power a remote off-board sensor which has a ratiometric output. Sensors with ratiometric outputs have an output voltage which is proportional to the supply voltage, as well as the parameter being sensed. Traditionally it is assumed that the supply voltage to the sensor is 5V and the same 5V is also used as the voltage reference to the analog to digital converter (ADC). However, in modern data acquisition systems, the voltage reference specified by the ADC is more often either 3.3V, 2.5V or 1.8V. This means the 5V full-scale signal from the sensor must be scaled down before the ADC input. Likewise, the 5V sensor supply is derived from the voltage reference and must be scaled up to 5V. The scaling creates inaccuracy in the acquisition system. This application note shows a technique to enable engineers to restore the accuracy of the acquisition by using a matched resistor divider RES11A-Q1.