NCP551(2004) Ver la hoja de datos (PDF) - ON Semiconductor

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componentes Descripción

Fabricante

NCP551
(Rev.:2004)

150 mA CMOS Low Iq Low-Dropout Voltage Regulator

ON Semiconductor 

NCP551, NCV551

Input

Q1

R

1

1.0 mF

2

3

Input

R1

Q1

R2

Q2

R3

Output

5

1

1.0 mF

1.0 mF

2

4

3

Output

5

1.0 mF

4

Figure 21. Current Boost Regulator

The NCP551 series can be current boosted with a PNP transis-

tor. Resistor R in conjunction with VBE of the PNP determines

when the pass transistor begins conducting; this circuit is not

short circuit proof. Input/Output differential voltage minimum is

increased by VBE of the pass resistor.

Figure 22. Current Boost Regulator with

Short Circuit Limit

Short circuit current limit is essentially set by the VBE of Q2 and

R1. ISC = ((VBEQ2 − ib * R2) / R1) + IO(max) Regulator

Input

Enable

1

1.0 mF

2

3

1

1.0 mF

2

3

R

C

Output

5

1.0 mF

4

Output

5

1.0 mF

4

Input

R

Q1

1.0 mF

11 V

Output

1

5

1.0 mF

2

3

4

Figure 23. Delayed Turn−on

If a delayed turn−on is needed during power up of several volt-

ages then the above schematic can be used. Resistor R, and

capacitor C, will delay the turn−on of the bottom regulator.

Figure 24. Input Voltages Greater than 12 V

A regulated output can be achieved with input voltages that

exceed the 12 V maximum rating of the NCP551 series with

the addition of a simple pre−regulator circuit. Care must be

taken to prevent Q1 from overheating when the regulated

output (Vout) is shorted to GND.

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