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PDF SC441A Data sheet ( Hoja de datos )
| Número de pieza | SC441A | |
| Descripción | High Efficiency Integrated Driver | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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SC441A
www.DataSheet4U.com
POWER MANAGEMENT
Features
High Efficiency Integrated Driver for
4-Strings of 150mA LEDs
Description
Wide input voltage range from 4.5V to 21V
36V maximum output voltage
Drives up to 40 WLEDs in 4 strings
Programmable LED current for up to 150mA per
string
+/- 2% string-to-string current matching
Up to 90% efficiency
Wide 0.2% to 100% PWM dimming range
Possible analog dimming
Integrated 2.5A power switch
700KHz switching frequency for small size
Adjustable OVP for cost-effective output cap selection
Open/short LED protection
Thermal protection with auto-recovery
Thermally enhanced TSSOP-20 EDP package
Fully WEEE and RoHS compliant
The SC441A is a high-efficiency multiple string WLED driv-
er with an integrated boost converter. It operates over a
wide input range from 4.5V to 21V with a maximum out-
put voltage of 36V and a 2.5A internal power switch. It
can drive up to forty WLEDs in 4 strings with current up
to 150mA per string. The string-to-string current match-
ing is 2% typical, 3% maximum. The overall efficiency is
greater than 90% due to the low current sense voltage
and a low-impedance internal power switch. The wide
PWM dimming range boasts a ratio of 500: 1.
The 700KHz switching frequency enables the user to op-
timize the external component sizes for efficiency. When
there are fewer than 10 LEDs in each string, users can ad-
just the output voltage protection yielding an allowable
reduction in associated costs, size and voltage ratings of
the output capacitor.
Applications
Medium-sized LCD panel
Notebook Display
Automotive Car Navigation Display
Sub-Notebook and Tablet Computer Displays
Portable Media Players
The SC441A also features comprehensive open and short-
circuit LED protection functions. It disables the corre-
sponding strings with LED open or LED short conditions
while maintaining normal operation of other, unaffected
LED strings. This feature allows LCD panels to remain view-
able even under LED failure, wire disconnect, or short-cir-
cuit conditions. The internal thermal shutdown protects
the IC from overheating at abnormal conditions.
The SC441A is available in a thermally-enhanced TSSOP-
20 EDP package.
Typical Application Circuit
Vin (4.5V -21V)
SW
VIN
EN
SW
VOUT
OOVVPPIINN
FFLAG
PWM
COMP
SC441A
OVPRTN
IOIO11- -44
IIOOSSEETT
AAGGNNDD
SS
EDP
PPGGNNDD
IOGND
PGND
4
1
2
4 Strings
10
July 23, 2009
www.semtech.com
1 page  
www.DataSheet4U.com
Typical Characteristics
UVLO Threshold vs. Temperature
4.36
4.35 Comp SINK SOURCE
4.34
4.33
4.32
4.31
4.30
4.29
-40
25
Temperature (oC)
105
UVLO Hysteresis vs. Temperature
247
246
245 SS SINK/SOURCE
244
243
242
241
240
239
238
237
-40 25 105
Temperature (oC)
COMP SINK / SOURCE Current
vs. Temperature
7.50
VIN = 12V
7.00
SINK 6.50 SINK
6.00
5.50
SOURCE 5.00 SOURCE
4.50
4.00
-40 25
Temperature (oC)
105
SS SINK / SOURCE Current
vs. Temperature
6.0
VIN = 12V
5.0 SOURCE
4.0
3.0
2.0 SINK
1.0
0.0
-40 25 105
Temperature (oC)
SC441A
VIN Quiescent Supply Current
vs. Temperature
3.20
3.10
3.00
2.90
2.80
2.70
2.60
2.50
-40
25
Temperature (oC)
105
SW Saturation Voltage at 1A
vs. Temperature
175
170
165
VIN = 4.5V
160
155 VIN = 12V
150
145 VIN = 21V
140
135
-40
25
Temperature (oC)
105
VOUT Pull Down Current Source
vs. Temperature
0.93
0.91
0.89 VIN = 4.5V
0.87
0.85
0.83
0.81 VIN = 21V
0.79
0.77 VOUT = VIN + 3V
0.75
-40 25 105
Temperature (oC)
LED Current Source SCP Threshold
vs. Temperature
2.410
2.405 VIN = 12V
2.400
2.395
2.390
2.385
2.380
2.375
2.370
2.365
2.360
-40 25 105
Temperature (oC)
Average LED Current Source Setting
vs. Temperature
150.7
150.6
150.5
150.4
150.3
150.2
150.1
150.0
149.9 VIN = 12V
149.8 RIOSET = 1.78kW
149.7
-40 25
105
Temperature (oC)
© 2009 Semtech Corporation
www.semtech.com
5 Page 
www.DataSheet4U.com
5
Block Diagram
FFLAG
4
3
HICCUP
ONE IO CHANNEL SHOWN
LED OPEN/SHORT/OVERSHOOT
CIRCUIT PROTECTION
FAULT-1
SC441A
2
DISABLE2
OSC
S
Q
R
ILIM
SW
SW
IO1
IOSET
LED CURRENT
SETTING
CURRENT
SOURCE
IOGND
VOUT
OVPIN
OVPRTN
0.9mA
SS
OVP
Detect
OVP
Fault
3V3
4.5uA
HICCUP
1uA
DISABLE1
ISENSE
SS
HICCUP
CONTROL
LOGIC
Fault
HICCUP
UVLO
TSD
UVLO & TSD
Bandgap
PGND
PGND
COMP
PWM
VIN
EN
AGND
Figure 1. SC441A Block Diagram
5432
© 2009 Semtech Corporation
www.semtech.com 11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet SC441A.PDF ] | |
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