
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
W
M
.
C
LX1992
High Efficiency LED Driver
P
RODUCTION
D
ATA
S
HEET
TM
C H A R A C T E R I S T I C C U R V E S
Figure 5: V
OUT
and Inductor Current Waveforms.
Channel 1: V
OUT
(AC coupled; 200mV/div)
Channel 2: Inductor Current (100mA/div.)
Configuration: V
IN
= 3.0V, V
OUT
= 13.0V, I
IN
= 65mA
Figure 6: V
OUT
and Inductor Current Waveforms.
Channel 1: V
OUT
(AC coupled; 100mV/div)
Channel 2: Inductor Current (100mA/div.)
Configuration: V
IN
= 3.0V, V
OUT
= 13.7V, I
IN
= 120mA
0
1
2
3
4
5
0
20
40
60
80
100
120
140
160
D
Figure 7: Gate Drive Voltage vs. Drive Current
at T = 25
C.
50%
60%
70%
80%
90%
0
2
4
8
10
12
14
16
18
6
E
Figure 8: Efficiency vs. LED Output Current.
Configuration: V
IN
= 3.0V, L = 47
μ
H, R
CS
= 4K
Note: Data taken from LXE1992 Evaluation Board
50%
60%
70%
80%
90%
100%
0
2
4
6
8
12
14
16
18
20
22
24
L10
E
Figure 9: Efficiency vs. LED Output Current.
Configuration: V
IN
= 5.0V, L = 47
μ
H, R
CS
= 4K
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 1K
resistor). This circuit will have VBAT -
1.25V across it and at the higher input voltages the 1K
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.
C
H
A
R
T
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