3

Application information

Figure 15. Application schematic

Vbat

VS

VO

C1

C2

C0

Input ceramic capacitor C2 ≥ 1 μF is necessary for the regulator to operate properly.

The other input capacitor C1 can be used as a backup supply for the application. The C0 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.

Tiny output capacitors reduce board space and BOM cost: stable operation with 2.2 μF capacitor min, 4.7 μF

recommended to improve load transient response. 5 Ω ≥ ESR ≥ 10 mΩ.

Figure 16. Stability plane

0

1

2

3

4

5

6

7

8

9

10

1

10

100

1000

COUT [μF]

UNTESTED AREA

STABILITY AREA

INSTABILITY AREA

Vs = 14 V, Vout = 5 V, Iout = 150 mA

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 IO = 300 mA is obtained. The high-precision of the output voltage (±2%) is

obtained with a pretrimmed reference voltage. The voltage regulator automatically adapts its own quiescent

current to the output current level. In light load conditions, the quiescent current goes down to Iq_LL = 3.5 µA.

L99VR03 operates with reduced input voltage (post regulation) minimizing the internal power dissipation and

maximizing the output current. During initial power-up, after a thermal shutdown and a short to ground event, the

regulator has a soft start incorporated to control initial current through the pass element and the output capacitor.

L99VR03

Applicationinformation

DS14803 - Rev 2

page 10/28