Rainbow-electronics MAX1848 Manuel d'utilisateur télécharger pdf (Page 4)

MAX1848

White LED Step-Up Converter in SOT23

4 _______________________________________________________________________________________

Typical Operating Characteristics

(See Typical Application Circuit, V+ = 3V, I

LED

= 15mA, L = 33µH, C

OUT

= 1µF, C

COMP

= 0.15µF, R

SENSE

= 5Ω, CTRL = 1V, 2 LEDs,

= +25°C, unless otherwise noted.)

2.5 3.53.0 4.0 4.5 5.0 5.5

EFFICIENCY vs. SUPPLY VOLTAGE

MAX1848 toc01

SUPPLY VOLTAGE (V)

EFFICIENCY (%)

2 LEDs

3 LEDs

OUT

= 15mA

03010 20 40 50 60

EFFICIENCY vs. LOAD CURRENT

MAX1848 toc02

LOAD CURRENT (mA)

EFFICIENCY (%)

2 LEDs

3 LEDs

SWITCHING FREQUENCY

vs. SUPPLY VOLTAGE

MAX1848 toc03

SUPPLY VOLTAGE (V)

SWITCHING FREQUENCY (MHz)

1.1

1.2

1.3

1.4

2.5 3.53.0 4.0 4.5 5.0 5.5

= +85°C

= +25°C

= -40°C

50ms/div

POWER-UP WAVEFORMS

CTRL

LED

38mA

MAX1848 toc04

15mA

RISE

= 15ms

COMP

= 0.15µF

50ms/div

POWER-UP WAVEFORMS

CTRL

LED

38mA

MAX1848 toc05

15mA

RISE

= 110ms

COMP

= 1µF

µs/div

SHUTDOWN WAVEFORMS

CTRL

LED

38mA

MAX1848 toc06

15mA

2µs/div

SHUTDOWN WAVEFORMS

CTRL

OUT

COMP

6.3V

4.9V

MAX1848 toc07

1.5V

OUT

EVENTUALLY

DECAYS TO V+ = 3V

5ms/div

LINE-TRANSIENT RESPONSE

OUT

LED

3.00V

3.50V

6.25V

500mV/div

MAX1848 toc08

15mA

10mA/div

COMP

= 0.15µF

20ms/div

CTRL

TRANSIENT RESPONSE

CTRL

OUT

LED

1.0V

2.0V

6.7V

6.3V

MAX1848 toc09

30mA

15mA

COMP

= 0.15µF

1 2 3 4 5 6 7 8 9

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Rainbow-electronics MAX1848 Manuel d'utilisateur Page 4

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