NCP1501
http://onsemi.com
6
Figure4.PWMCircuitSchematic
Sync
V
bat
C1
10m
C2
10m
R3
R4
--
+
--
+
Q2
V
ref
ERROR
AMP
Latch
Q
S
R
En
--
+
OCP
Q1
L1
10mH
V
ref
+5%
Load
IPFET
R2
R1
COMP
OVP
COMP
Set
Ramp
En
LDOMode
When the synchronization pulse is not present, the
NCP1501 operates as an LDO. The DC/DC Control
CircuitrywillrelinquishcontrolofQ1andturnoffQ2.The
LDOControlCircuitrywillturnonQ3asabypasscircuitto
theinductor.Q1isthecontrollingpassdeviceoftheLDO
thatregulatestheinputtooutputvoltagedropout.TheLDO
cansourceanoutputcurrentinexcessof50mA.
Figure5.LDOCircuitSchematic
Sync
V
bat
C1
10m
C2
10m
R3
R4
--
+
V
ref
ERROR
AMP
Switch/Invert
Out
In
En
Q1
L1
10mH
Load
Set
Ramp
En
Q3