ISL1903
OBSOLETE PRODUCT
ENT
NO RECOMMENDED REPLACEM
nter at
contact our Technical Support Ce
om/tsc
1-888-INTERSIL or www.intersil.c
DATASHEET
FN8285
Rev 1.00
September 20, 2012
Dimmable Buck LED Driver - AC Mains or DC Input LED Driver
The ISL1903 is a high-performance, critical conduction mode
(CrCM), single-ended buck LED driver controller. It may be used
with DC input converters, but also supports single-stage
conversion of the AC mains to a constant current source with
power factor correction (PFC). The ISL1903 supports buck
converter topologies, such as isolated forward converters or
non-isolated source return buck converters. Operation in CrCM
allows near zero-voltage switching (ZVS) for improved
efficiency while maximizing magnetic core utilization.
The ISL1903 is compatible with both leading and trailing edge
modulated AC mains dimmers. It provides all of the features
required for high-performance dimmable LED ballast designs.
Features
• Excellent LED current regulation over line, load, and
temperature
• 0 - 100% dimming with leading-edge (triac) and
trailing-edge dimmers
• Power factor correction for up to 0.995 power factor and
less than 20% harmonic content
• Critical conduction mode (CrCM) operation for
quasi-resonant high efficiency performance
• Supports Universal AC Mains Input
• Configurable for PWM or DC current dimming control of
LEDs
• Monitors FET switching current for load regulation
• Supports isolated and non-isolated buck topologies
• Closed loop soft-start for no overshoot
• OFFREF feature to set dimming off-point to improve fixture
performance matching
• -40°C to +125°C operation
• Pb-free (RoHS compliant)
Applications
• Industrial and commercial LED lighting
• Retrofit LED lamps with triac dimming
• Universal AC mains input LED retrofit lamps
• AC or DC input LED ballasts
100
90
80
1
5
VDD
14
CS+
AC
OUT
12
LED CURRENT (%)
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
DHC
16
ISL1903
EMI Filter
8
DELADJ
GND
VREF
RAMP
IOUT
4
OC
VERR
FB
6
13
9
Dimmer
3
7
AC Mains
10
CONDUCTION ANGLE (%)
FIGURE 1A. BOOST-RETURN (BUCK) TOPOLOGY
FIGURE 1B. CURRENT vs AC CONDUCTION ANGLE
FIGURE 1. ISL1903 APPLICATION PERFORMANCE
FN8285 Rev 1.00
September 20, 2012
Page 1 of 19
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