ST1208

V1.1

9/12

2004/10/27

LED CURRENT vs. SUPPLY VOLTAGE

12

13

14

15

16

17

18

19

2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5

SUPPLY VOLTAGE ( V )

LED1

LED2

LED3

EFFICIENCY ( PLEDs / PBATT ) vs.

Li + BATTERY DISCHARGE

40

50

60

70

80

90

4.2

4.1

4.0

3.9

3.8

3.7

3.6

3.5

3.4

Li+ BATTERY VOLTAGE,

TIME-WEIGHTED ( V )

45mA

60mA

90mA

100mA

! Typical Operating Characteristics

Condition: VIN = VEN1 = VEN2 = 3.6 V, CIN = C1 = C2 = COUT = 1 uf, dropout current is 60 mA. ( 20 mA / LED X 3 ), LED

forward voltage Vf = 3.3 V, ISET = 125 uA

Under-Voltage Protection

0

10

20

30

40

50

60

IIN ( mA )

Increase

Reduce

ILED vs. ISET

0

10

20

30

40

50

10

30

60

90

12

0

15

0

18

0

21

0

24

0

ISET ( uA )

VIN = 2.7 V

VIN = 3.0 V

VIN = 3.3 V

VIN = 3.6 V

VIN = 4.2 V

VIN = 5.0 V

ILED = 30 mA @ Iset = 190

VIN = 2.7 V

VIN = 3.0 V

VIN > 3.3 V