NCP3065, NCV3065
http://onsemi.com
10
Figure 17. Buck Demo Board with External Switch Application Schematic
J1
1
15 k
1.8 nF
C2
C1
C4
R13
U1
NCP3065
5
36
4
8
7
1
2
COMP
TCAP
GND
N.C. SWC
SWE
R10
D1
MBRS140LT3G
J3
GND
1
J2
1
L1
0.1 mF
220 mF / 50 V
+
0.1 mF
V
CC
I
PK
470 mH
+
J5
1
J7
1
J6
ON/OFF
1
1
R1 R2 R3 R4 R5 R6 R7
R11
Q1 Q2
10 k
R9
J4
+VAUX
+VIN
BC807−LT1G
BC817−LT1G
6x 1R0 ±1%R
1206 1206 1206 1206 1206 1206 1206
NU
C6
+LED
−LED
GND
R12
NU
R14
NU
1 k0805
R
SENSE
±1%
C5 100 pF
R8
C3
SOIC8
CT
1208
D2
R15
1 k
Q5
Q4
MMBT3904LT1G
NTF2955
MMSD4148
0R10
J6
1
R11
ON/OFF
This design illustrates the NCP3065 being used as a PFET
controller, the design has been optimized for continuous
current operation with low ripple which allows the output
filter capacitor to be eliminated. Figure 20 illustrates the
efficiency with 1 and 2 LEDs and output currents of 350 mA
and 700 mA. Additional data and design information can be
found of this design in Application Note AND8298.
Value of Components
Name Value
C1, C4 100 nF, Ceramic Capacitor, 1206
C2
220 mF, 50 V, Electrolytic Capacitor
C3 1.8 nF, Ceramic Capacitor, 0805
C5 100 pF, Ceramic Capacitor, 0805
D1 1 A, 40 V Schottky Rectifier
D2 MMSD4148
L1
470 mH, DO5022P−474ML Coilcraft Inductor
Q4 NTF2955, P−MOSFET, SOT223
Name Value
Q5 MMBT3904LT1G, SOT23
R1
100 mW, 0.5 W
R8 15 k, resistor 0805
R9
10 kW, resistor 0805
R10, R15
1 kW, resistor 0805
R11
1.2 kW, resistor 0805
R12 R
SENSE
±1%, 1206
U1 NCP3065, SOIC8
NOTE: R
SENSE
is used to select LED output current, for 350 mA use 680 mW, for 700 mA use 330 mW and for 1000 mA use 220 mW
Test Results (without output capacitor)
Test Condition Results
Line Regulation V
in
= 9 V to 35 V, I
o
= 350 mA 12 mA
Load Regulation V
in
= 12 V, I
o
= 350 mA, V
o
= 3 V to 8 V 13 mA
Output Ripple V
in
= 9 V to 35 V, I
o
= 350 mA < 15% I
O
Efficiency V
in
= 12 V, I
o
= 350 mA, V
OUT
= 3 to 8 V > 75%
