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PDF SC635 Data sheet ( Hoja de datos )
| Número de pieza | SC635 | |
| Descripción | Charge Pump Flash LED Driver | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC635 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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POWER MANAGEMENT
Description
Features
SC635
Charge Pump
Flash LED Driver
The SC635 is a high-current charge pump designed spe-
cifically for use with white LEDs used in camera flash ap-
plications. Only two small bucket capacitors are required
to develop the output drive, providing a low EMI solution
compared to inductive boost regulators.
The SC635 has two modes of operation: Flash mode and
Spotlight mode. In Flash mode, the SC635 is capable of
delivering 200mA to a high-intensity LED during image
capture. In Spotlight mode the SC635 outputs 40% of the
Flash mode current for general purpose lighting or status
indication.
u Two selectable modes - Flash and Spotlight
u 200mA max output - Flash Mode
u Spotlight mode set to 40% of Flash Current
u 3.0V to 5.25V Input Range
u External pins for control of flash and spotlight modes
for synchronization to a camera module or graphics
controller
u Short circuit, over-voltage, and over-temperature
protection
u Soft-start functionality
u Micro Lead Package MLPD-10, 3mm x 3mm
An external resistor is connected in series with the LED to
set the current. In Flash mode, this resistor can dissipate
up to 50mW, reducing the power dissipation requirement
of the SC635. The flash input (FLASH) overrides the con-
trol input (CTRL) to make sure the flash function is acti-
vated when called for.
The thermally efficient MLPD-10 package and ceramic by-
pass and bucket capacitors make the SC635 a high out-
put current driver that requires minimal PCB area.
Applications
u Mobile Camera Phones
u Digital Cameras
u PDAs with Built-in Cameras
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Typical Application Circuit
Typical Application Circuit
VBAT
10µF
1µF
1µF
FLASH
CTRL
1 VIN SC635 VOUT 9
8 C1+
GND 3
4 C1-
ISET 6
10 C2+
CTRL 7
2 C2-
FLASH 5
1µF
white LED
RSET
December 2, 2005
www.semtech.com
datasheet pdf - http://www.DataSheet4U.net/
1 page  
SC635
POWER MANAGEMENT
PAipnpClicoantfiogunrsaItniofonrmation
General Operation
The SC635 is a powerful 2X charge pump designed to
drive a high-intensity white LED with a constant current
(Spotlight mode) or with a pulsed current of higher inten-
sity (Flash mode) used for camera flash.
In Flash mode the SC635 output can drive 200mA at
4.25V into an LED for an unlimited duration under all
temperature and input conditions. The FLASH pin is used
to trigger this mode (active high). In Spotlight mode the
SC635 regulates the output current to 40% of the Flash
mode current setting when the CTRL pin is pulled high
and the FLASH pin is low. Note that Flash mode has prior-
ity over Spotlight mode, i.e., the FLASH pin triggers Flash
mode regardless of the state of the CTRL pin.
Output current is regulated by attaching the ISET pin to
the cathode(s) of the LED package and a low resistance
sense resistor (typically 1.25Ω). The ISET pin monitors
the voltage at the cathode and signals the charge pump
to increase or decrease the output current until the ISET
voltage reaches the programmed setting. The resistor
value is chosen to set the current through the LED based
on this reference voltage.
Flash Mode
Flash mode is enabled whenever the FLASH pin is pulled
high and remains active until the FLASH pin is released.
This mode has higher priority than Spotlight mode, so the
state of the CTRL pin is overridden whenever the FLASH
pin is activated. While in Flash mode the reference volt-
age on the ISET pin is set to 250mV.
the output current being set too low.
Protection Circuitry
The SC635 also provides protection circuitry that prevents
the device from operating in an unspecified state. These
functions include Input Over-Voltage Protection (IOVP),
Output Over-Voltage Protection (OVP), Over-Temperature
(OT) Protection, Over-Current Protection (OCP), and Short-
Circuit Current Protection (SCCP).
Input Over-Voltage Protection
Input over-voltage protection is included to prevent opera-
tion at high input voltages that could damage the device.
The IOVP circuit senses the input voltage and determines
when the supply exceeds 6V. Hysteresis is included in this
circuit to avoid chattering between states. When the volt-
age rises above this threshold, the device is disabled un-
til the input voltage drops to a level within the specified
range.
Output Over-Voltage Protection
Output over-voltage protection is included to prevent the
SC635 from generating an output voltage that could dam-
age other devices connected to it such as load LEDs andhttp://www.DataSheet4U.net/
bypass capacitors. When the output voltage exceeds 5.5V,
the OVP circuit disables the charge pump until the voltage
decreases to a level within the acceptable range. This
circuit allows the device to drive LEDs with high forward
voltages at a reduced level without exceeding the output
voltage limits specified for the device. Note, however, that
this effect is a consequence of the OVP circuit and is not
its intended purpose.
Output currents other than the rated maximum of 200mA Over-Temperature Protection
can be set by changing
IOUT = 250mV/RISET.
the
RISET
value. In
Flash
mode,
The over-temperature circuit helps prevent the device
from overheating and experiencing a catastrophic fail-
ure. When the junction temperature exceeds 150°C the
Spotlight Mode
device is disabled. It remains disabled until the junction
Spotlight mode is enabled by setting the CTRL pin high temperature drops below this threshold. As with the UVLO
and keeping the FLASH pin low. When in Spotlight mode, and OVP circuits, hysteresis is included to prevent toggling
the SC635 can maintain a constant current indefinitely to between modes.
drive an LED or bank of LEDs. The ISET reference voltage
is set to 100mV so that the output current is maintained Over-Current Protection
at 80mA when a 1.25Ω resistor is used. Spotlight current When the SC635 is in 2X mode, the input current will
iIusneasslpwhooatuylisgldh4tn0om%toeodxfecf,elaIeOsdhU2TcΩu=r,r1he0nowt0fmeovrVe/ar,RntyIoSEgTe.i vn eTsnhuerveareltuhseeisoStofCrR6vI3SaE5Tl.-
be approximately double the required output. When the
steady-state load requires the maximum current available
in 2X mode, the OCP circuit prevents the device from over-
does not become unstable while in Spotlight mode due to heating due to excessive power dissipation.
2005 Semtech Corp.
www.semtech.com
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
POWER MANAGEMENT
Outline Drawing - MLPD-10
SC635
AE
PIN 1
INDICATOR
(LASER MARK)
aaa C
LxN
C
12
B
E
A
A1
A2
C
DIMENSIONS
DIM
INCHES
MIN NOM MAX
MILLIMETERS
MIN NOM MAX
A .031 - .039 0.80 - 1.00
A1 .000 - .002 0.00 - 0.05
A2 - (.008) -
- (0.20) -
b .007 .009 .011 0.18 0.23 0.30
C .074 .079 .083 1.87 2.02 2.12
D .042 .048 .052 1.06 1.21 1.31
E .114 .118 .122 2.90 3.00 3.10
e .020 BSC
0.50 BSC
L .012 .016 .020 0.30 0.40 0.50
N 10
10
aaa .003
0.08
bbb .004
0.10
SEATING
PLANE
D
N
e
bxN
bbb
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CAB
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.
Marking Information
Top Mark
635
yyww
xxxx
yyww = Datecode (Example = 0552)
xxxx = Semtech Lot Number
2005 Semtech Corp.
11
www.semtech.com
datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet SC635.PDF ] | |
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