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