CAT37 Datasheet, PDF (9/13 Pages) Catalyst Semiconductor – CMOS White LED Driver Boost Converter

CAT37
TYPICAL APPLICATION CIRCUITS
The application diagrams are shown for the SOT23 pin numbers.
Two LEDs with DC Level Dimming Control
Efficiency - Two LEDs
VIN
3 V to 4.2 V
D1
5
1 VDC
VIN
SW ^Dimming
CAT37
18k
4 _SHDN
3
1k
FB
GND
2
15mA
90
85
80
75
70
65
60
0
V^VI^IN^N = ^3..⁶6^VV
V^VIN ⁼= ³3^..⁰0^VV
5 10 15 20 25 30
LED CURRENT [mA]
Three LEDs with DC Level Dimming Control
VIN
3 V to 4.2 V
D1
5
1 VDC
VIN
SW ^Dimming
CAT37
18k
1k
4 _SHDN
3
FB
GND
2
15mA
Efficiency - Three LEDs
90
85
80
75
70
65
60
0
VVININ==33.6.6VV
VIN =^VI3^N.0⁼³V^.0V
5 10 15 20 25 30
LED CURRENT [mA]
Four LEDs with PWM Dimming Control
VIN
3 V to 4.2 V
D1
PWM
5
1 10k
VIN
SW
CAT37
18k
4 _SHDN
3
1k
FB
GND
2
15mA
Efficiency - Four LEDs
90
85
80
75
70
65
60
0
VVININ==33..66VV
VVIINN=33.0.0VV
5
10 15 20
25 30
LED CURRENT [mA]
9
Doc No. 5005, Rev. R