ADP3300
Constant Dropout Post Regulator
The circuit in Figure 6 provides high precision with low drop-
out for any regulated output voltage. It significantly reduces the
ripple from a switching regulator while providing a constant
dropout voltage, which limits the power dissipation of the LDO
to 15 mW. The ADP3000 used in this circuit is a switching
regulator in the step-up configuration.
VIN = 2.5V TO 3.5V
C1
100F
10V
L1
6.8H
R1
120⍀
ILIM
VIN
SW1
ADP3000-ADJ
GND SW2 FB
D1
1N5817
C2
100F
10V
ADP3300-5
IN
OUT
SD
R2
30.1k⍀
1%
GND
Q1
2N3906
R3
124k⍀
1%
5V @ 50mA
C3
2.2F
Q2
2N3906
R4
274k⍀
Figure 6. Constant Dropout Post Regulator
–8–
REV. C