MP1521
High Efficiency
White LED Driver
Monolithic Power Systems
Application Circuits
Figure 3: One String of Four (4) LEDs
Efficiency vs LED current using
47µH Toko D62CB Inductor
Efficiency (%)
90
85
V
IN
D1, B130
1
L
47µH
C
IN
4.7µF
IN
SW
10
V
IN
= 4V
V
IN
= 3V
5
10
15
20
ON
MP1521
EN
2
C
OUT
1µF
GND
80
75
OFF
EN
GND
9
White LEDs
3
REF
OLS
8
LED Current mA
Line regulation using
47µH Toko D62CB Inductor
BRT
4
BRT
FB1
7
LED Current (mA)
22
21
20
19
18
17
16
15
2.4
5
FB3
FB2
6
20
3.0
V
IN
(V)
3.6
4.2
Figure 4: One String of Six (6) LEDs (Low inductor height for portables)
L1
D1, B130
1
V
IN
C
IN
4.7µF
85
Efficiency (%)
Efficiency vs V
IN
using 1.2mm High
Sumida CMD4D11 Inductor
IN
SW
10
ON
OFF
MP1521
EN
2
C
OUT
1µF
GND
9
GND
80
75
6.8µH
10µH
15µH
EN
3
REF
OLS
8
70
BRT
4
BRT
FB1
7
White LEDs
2.5
3
3.5
4
4.5
V
IN
(V)
5
FB3
FB2
6
LED Current (mA)
Line regulation using 1.2mm High
Sumida CMD4D11 Inductor
23.0
21.0
19.0
17.0
15.0
20
6.8µH
10µH
15µH
2.5
3
3.5
4
4.5
V
IN
(V)
MP1521 Rev 2.7 10/06/04
www.monolithicpower.com
6
MPS [ MONOLITHIC POWER SYSTEMS ]
