EL1848
Block Diagram
2.6V TO
5.5V
C
IN
4.7µF
REFERENCE
GENERATOR
1MHz
OSCILLATOR
THERMAL
SHUTDOWN
OVER-VOLTAGE
PROTECTION
V
OUT
LX
PWM
LOGIC
C
OUT
1µF
L
33µH
V
IN
COMP
C
COMP
0.1µF
+
+
+
BOOST
I-SENSE
START-UP
CONTROL
I(LED)
PGND
C
S
5Ω
PWM
SIGNAL
617K
50K
ERROR AMP
+
-
V
CNTL
CNTL
SGND
Typical Performance Curves
All performance curves and waveforms are taken with C
1
= 4.7µF, C
2
= 1µF, C
3
= 0.1µF, L = 33µF, V
IN
= 3.3V, V
CNTL
= 1V, R
1
= 5Ω, 3 LEDs in a
series; unless otherwise specified.
1.05
1.04
1.03
1.02
1.01
1
2.5
3.5
3
2.5
F
S
(MHz)
I
IN
(µA)
2
1.5
1
0.5
3
3.5
4
V
IN
(V)
4.5
5
5.5
0
2.5
4.5
6.5
8.5
V
IN
(V)
10.5
12.5
14.5
V
CNTL
=0V, 0.1V
WHITE LEDs DISCONNECTED
FIGURE 1. SWITCHING FREQUENCY vs V
IN
FIGURE 2. QUIESCENT CURRENT
4
INTERSIL [ INTERSIL CORPORATION ]
