TLE42994

Application Information

Data Sheet

29

Rev. 1.2, 2014-07-03

6.2

Selection of External Components

6.2.1

Input Pin

The typical input circuitry for a linear voltage regulator is shown in the application diagram above.

A ceramic capacitor at the input, in the range of 100 nF to 470 nF, is recommended to filter out the high frequency

disturbances imposed by the line e.g. ISO pulses 3a/b. This capacitor must be placed very close to the input pin

of the linear voltage regulator on the PCB.

An aluminum electrolytic capacitor in the range of 10 µF to 470 µF is recommended as an input buffer to smooth

out high energy pulses, such as ISO pulse 2a. This capacitor should be placed close to the input pin of the linear

voltage regulator on the PCB.

An overvoltage suppressor diode can be used to further suppress any high voltage beyond the maximum rating

of the linear voltage regulator and protect the device against any damage due to over-voltage.

The external components at the input are not mandatory for the operation of the voltage regulator, but they are

recommended in case of possible external disturbances.

6.2.2

Output Pin

An output capacitor is mandatory for the stability of linear voltage regulators.

The requirement to the output capacitor is given in “Functional Range” on Page 12. The graph “Output

Capacitor Series Resistor ESR(CQ) versus Output Current IQ” on Page 17 shows the stable operation range

of the device.

TLE42994 is designed to be stable with extremely low ESR capacitors. According to the automotive environment,

ceramic capacitors with X5R or X7R dielectrics are recommended.

The output capacitor should be placed as close as possible to the regulator’s output and GND pins and on the

same side of the PCB as the regulator itself.

In case of rapid transients of input voltage or load current, the capacitance should be dimensioned in accordance

and verified in the real application that the output stability requirements are fulfilled.