NCP500 ON, NCP500 Datasheet - Page 16

• Manufacturer Part Number: NCP500
• Description: 150 mA CMOS Low Noise Low-Dropout Voltage Regulator
• Manufacturer: ON

Enable
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.
Input
Figure 32. Delayed Turn−on
R
1.0 mF
1.0 mF
C
1
2
3
1
2
3
Input
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
(V
R
out
Figure 34. Input Voltages Greater than 6.0 V
5.6 V
) is shorted to G
5
4
5
4
Q1
1.0 mF
1.0 mF
1.0 mF
Output
Output
nd.
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NCP500
16
2.5
1.5
0.5
1
2
3
4
3
2
1
0
3
2
1
0
0
The graph shows the delay between the enable signal and
output turn−on for various resistor and capacitor values.
10
20
5
4
No Delay
Figure 33. Delayed Turn−on
R = 1.0 MW
C = 0.1 mF
30
40
1.0 mF
Output
Time (ms)
50
60
70
R = 1.0 MW
C = 1.0 mF
T
V
V
80
A
in
out
= 25 C
= 3.4 V
= 2.8 V
90
100
110