Microsemi

Linfinity Microelectronics Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 9

Copyright

© 2000

Rev. 1.1b, 2005-03-03

LX1992

High Efficiency LED Driver

TM

®

CHARACT ER I S TI C CURVES

Channel 2: Inductor Current (100mA/div.)

Channel 2: Inductor Current (100mA/div.)

0

1

2

3

4

5

0

20

40

60

80

100

120

140

160

Driv e Current (mA)

Figure 7: Gate Drive Voltage vs. Drive Current

at T = 25

50%

60%

70%

80%

90%

0

2

4

6

8

1012

14

1618

LED Current (mA)

Figure 8: Efficiency vs. LED Output Current.

Note: Data taken from LXE1992 Evaluation Board

50%

60%

70%

80%

90%

100%

0

2

4

6

8

10

1214

1618

2022

24

LED Current (mA)

Figure 9: Efficiency vs. LED Output Current.

Note: Data taken from LXE1992 Evaluation Board

Efficiency Measurement Hint

: When doing an efficiency

evaluation using the LX1992 Evaluation Board, VPOT should

be driven by a separate voltage supply to account for losses

associated with the onboard reference (i.e., the 1.25V shunt

regulator and 1KΩ resistor). This circuit will have VBAT -

1.25V across it and at the higher input voltages the 1KΩ

resistor could have as much as 4mA through it. This shunt

regulator circuitry will adversely effect the overall efficiency

measurement and is not normally used in an application.

Therefore it should not be considered when measuring

efficiency.