1.2A White LED Regulating Charge Pump for

Camera Flashes and Movie Lights

4

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LED CURRENT vs. TEMPERATURE

TEMPERATURE (

°C)

60

35

10

-15

205

210

215

220

225

200

-40

85

Ω

EN1 LOW

EN2 HIGH

Ω)

0.8

0.6

0.4

0.2

0.4

0.6

0.8

1.0

1.2

0

0.2

1.0

EN1 AND EN2 HIGH

EN1 HIGH, EN2 LOW

EN1 LOW, EN2 HIGH

TYPICAL OPERATING WAVEFORMS

IN 1x MODE

MAX1577 toc09

400ns/div

50mV/div

(AC-COUPLED)

50mV/div

(AC-COUPLED)

50mV/div

(AC-COUPLED)

TYPICAL OPERATING WAVEFORMS

IN 2x MODE

MAX1577 toc10

400ns/div

50mV/div

(AC-COUPLED)

50mV/div

(AC-COUPLED)

50mV/div

(AC-COUPLED)

STARTUP AND SHUTDOWN RESPONSE

MAX1577 toc11

400

µs/div

2V/div

2V/div

0V

0mA

500mA/div

LED CURRENT vs. PWM DUTY CYCLE

DUTY CYCLE (%)

80

60

40

20

200

400

600

800

1000

1200

0

0100

Ω

EN1 PWM

EN2 HIGH

EFFICIENCY vs. SUPPLY VOLTAGE

WITH PWM DIMMING

SUPPLY VOLTAGE (V)

5.1

4.7

4.3

3.9

3.5

3.1

30

20

10

40

50

60

70

80

0

2.7

5.5

25%

50%

75%

Ω

EN1 PWM

EN2 HIGH

DIMMING RESPONSE

MAX1577 toc14

100

µs/div

2V/div

2V/div

0V

0mA

500mA/div

Typical Operating Characteristics (continued)