NCV551SN14T1G(2013) データシートの表示（PDF） - ON Semiconductor

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NCV551SN14T1G
(Rev.:2013)

150 mA CMOS Low Iq Low-Dropout Voltage Regulator

ON Semiconductor 

NCP551, NCV551

Input

Q1

R

1

1.0 mF

2

3

Output Input

Q2

R1

Q1

R2

R3

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 transist-

or. 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.

Input

Enable

1

1.0 mF

2

3

Output

5

1.0 mF

4

1

1.0 mF

2

3

R

C

Output

5

1.0 mF

4

Figure 23. Delayed Turn−on

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

voltages then the above schematic can be used. Resistor R,

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

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

R

Q1

1.0 mF

11 V

Output

1

5

1.0 mF

2

3

4

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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