NCP500

http://onsemi.com

16

Output

1

2

3

5

4

Input

1.0

mF

1.0

mF

Q1

R

5.6 V

A regulated output can be achieved with input voltages that ex-

ceed the 6.0 V maximum rating of the NCP500 series with the

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

to prevent Q1 from overheating when the regulated output

Output

1

2

3

5

4

Input

1.0

mF

1.0

mF

Output

1

2

3

5

4

Enable

1.0

mF

1.0

mF

C

0

3

3

80

2.5

2

90

40

30

110

Time (ms)

2

1

1.5

20

4

1

0.5

0

100

70

60

50

10

0

R = 1.0 M

W

C = 1.0

mF

R = 1.0 M

W

C = 0.1

mF

No Delay

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. A

few values were chosen and the resulting delay can be seen in

Figure 33.

The graph shows the delay between the enable signal and

output turn−on for various resistor and capacitor values.

R

Figure 32. Delayed Turn−on

Figure 33. Delayed Turn−on

Figure 34. Input Voltages Greater than 6.0 V