L5150CS datasheet(14/34 Pages) STMICROELECTRONICS

14 / 34 page

Application information

L5150CJ, L5150CS

14/34

DS6184 Rev 18

Application information

3.1

Voltage regulator

The voltage regulator uses a p-channel mos transistor as a regulating element. With this

structure a very low dropout voltage at current up to 150 mA is obtained. The output voltage

is regulated up to input supply voltage of 40 V. The high-precision of the output voltage

(±2%) is obtained with a pre-trimmed reference voltage. The voltage regulator automatically

adapts its own quiescent current to the output current level. In light load conditions the

quiescent current goes to 55 µA only (low consumption mode). This procedure features a

certain hysteresis on the output current (see Figure 7). Short-circuit protection to GND and a

thermal shutdown are provided.

Figure 21. Application schematic

The input capacitor C1 ≥ 100 µF is necessary as backup supply for negative pulses which

may occur on the line. The second input capacitor C2 ≥ 220 nF is needed when the C1 is too

distant from the VS pin and it compensates smooth line disturbances. The C0 ceramic

capacitor, connected to the output pin, is for bypassing to GND the high-frequency noise

and it guarantees stability even during sudden line and load variations. Suggested value is

C0 = 220 nF with ESR ≥ 100 mΩ.

Stability region is reported in Figure 22.

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