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PDF SC4541 Data sheet ( Hoja de datos )
| Número de pieza | SC4541 | |
| Descripción | High Frequency LED Driver | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC4541 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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SC4541
POWER MANAGEMENT
Features
High Frequency LED Driver with
Integrated Schottky and Simple Interconnect
Description
VIN Range — 2.9V to 22V
VOUT Range — Up to 25V
IOUT Range:
Up to 100mA (Boost)
Up to 200mA (Buck)
Drives Up to 7 Series WLEDs (Boost)
Drives Up to 5 Series WLEDs (Buck)
Integrated Schottky Rectifier
Single-Wire LED Connect
Current Mode Control
Frequency — 2.0MHz
No External Compensation
Direct PWM Dimming
100:1 Range at 500Hz
Open-LED Protection — 27V
Low Shutdown Current < 1µA
Package Options:
Low Profile MLPD-UT, 6-pin 2x2 x0.6(mm)
SOT23, 6-pin 2.9x2.8 x1.45(mm)
Lead-free, Halogen-Free and WeEE/RoHS Compliant
Applications
Keypad Illumination
DSC and DSLR Display Backlight
Cellular Handsets
Automotive Lighting
The SC4541 is a fully integrated, high voltage boost (step-
up) and buck (step-down) LED driver. The input voltage
range is 2.9V to 22V with output voltage up to 25V. The
device is capable of driving up to 7 white LEDs. The high
side sense enables a single-wire LED connection by taking
advantage of the available system ground. This reduces
connector cost and complexity.
The device includes a current mode PWM controller,
260mA power switch, and high performance Schottky
rectifier. The LED driver eliminates external compensation
components for minimum solution size.
The wide input voltage range and low standby current are
ideal for portable devices. The high input voltage allows
direct connection to multi-cell battery packs which
increases operating efficiency and extends battery life.
Output current is programmed with an external sense
resistor up to 100mA (Boost) or 200mA (Buck). The device
provides ±5% constant current accuracy across the entire
operating temperature range.
A logic level PWM dimming signal may be applied directly
to the enable (EN) pin - for direct PWM dimming with a
wide dimming range. Output OVP (over voltage protec-
tion) protects the SC4541 from open circuit faults in the LED
string or connector. External OVP programming resistors
are not required.
The SC4541 is available in low profile MLPD-UT and
SOT23,6-pin packages. The device is rated across the
temperature range -40°C to +85°C.
Typical Application Circuit
VIN 2.9V to 22V
Boost Topology IOUT up to 100mA
L1
C1 10μF
1μF
IN SW OUT VOUT Up to 25V
SC4541
C2
1μF
RS
10Ω
PWM
Dimming
EN GND FB
7 WLED @
20mA
Version 1.3
© 2011 Semtech Corporation
1
1 page  
SC4541
Typical Characteristics
VIN = 10V
2.0
EN Threshold
1.6
Switch1.2ing Frequency(SS302R2)
0.8
0.4
0.0
-40
2.4
VIN = 5V
VIN = 12V
VIN = 22V
2.2
25
Temperature (oC)
Switching Frequency
85
2.0
1.8
1.6
-40
Temper2a5ture (oC)
VSW = 10V
2.0
Switch Leakage Current
1.6
1.2
0.8
0.4
0.0
-40
25
Temperature (oC)
85
85
500
400
300
200
100
0
-40
30.0
Switch Current Limit
25
Temperature (oC)
Output Over Voltage Protection
85
25.0
20.0
15.0
10.0
-40
25
Temperature (oC)
85
5
5 Page 
SC4541
Applications Information ( continued)
The converter has higher efficiency under CCM and the
inductor peak current is calculated by the following
equation.
IL _ PEAK
IIN
VIN u D
2 u FS u L
Assuming CCM, the duty ratio is calculated using the fol-
lowing equation.
D VOUT VIN VD
VOUT VD
VD is the forward voltage drop of the internal Schottky
rectifier.
The inductor ripple current is further shown by the follow-
ing equation.
A 1µF ceramic input and output capacitor should be ade-
quate for most applications. Larger capacitance reduces
voltage ripple, overshoot and undershoot during load
transient as well as improving loop stability margin.
Recommended ceramic capacitor manufacturers are
listed in Table 1.
Table 2 — Recommended Ceramic Capacitor
Manufacturers
Vendor
Phone
Website
Kemet
408-986-0424
www.kemet.com
Murata
814-237-1431
www.murata.com
Taiyo Yuden
408-573-4150
www.t-yuden.com
IL _ RIPPLE
VIN u D
FS u L
The recommended inductance shown in Table 1 is based
on operation with regulated 5V input, dual Li-ion or three
Li-ion battery packs. Increased inductance is required for
higher input and output voltage configurations.
Table 1 — Inductance Requirements, Driving 6 bWLED
Input Type
Input Voltage
Range
L1 Induc-
tance
Regulated 5V
4.5 to 5.5V
10µH
Dual Lithium Ion Battery Pack
5.4 to 8.4V
22µH
Three Lithium Ion Battery Pack
8.1 to 12.6V
33µH
Output Capacitor Selection
Ceramic capacitors are placed near IN and OUT pins to
ground in order to minimize ripple voltage. The minimum
capacitance needed for a given ripple can be estimated
using the following equation.
COUT
VOUT VIN u IOUT
VOUT u FS u VRIPPLE
VRIPPLE = Peak to peak output voltage ripple
IOUT = Output current
VOUT = Boost output voltage
VIN = Input voltage
FS = Switching frequency
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet SC4541.PDF ] | |
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