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PDF ZXSC380 Data sheet ( Hoja de datos )
| Número de pieza | ZXSC380 | |
| Descripción | Single or multi cell LED driver solution | |
| Fabricantes | Zetex Semiconductors | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ZXSC380 (archivo pdf) en la parte inferior de esta página. Total 10 Páginas | ||
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ZXSC380
Single or multi cell LED driver solution
www.DataSheet4U.com
Description
The ZXSC380 is a highly integrated single or
multi cell LED driver for applications where
step-up voltage conversion from a very low
input voltage is required. These applications
mainly operate from 1.5V or 1.2V cells. The IC
generates constant current pulses that are
ideal for driving single or multiple LEDs over
a wide range of operating voltages. The
ZXSC380 provides a simple to use, low cost,
space saving and easy to layout solutions.
The ZXSC380 uses a PFM control technique to
drive an internal switching transistor which
has a low saturation resistance. This ensures
high efficiency, even for input voltages as low
as 1V.
Features
• 80% efficiency
• User adjustable output current
• Single cell operation
• Low saturation voltage switching transistor
• Simple application circuit
• Low external component count
• SOT23 package
• Available also in die form
Pin connections
The IC can start up under full load and operates
down to an input voltage of only 0.9V typical.
The ZXSC380 is offered in the space saving
SOT23 package or in die form, offering an
excellent cost vs performance solution for
single cell LED driving applications.
Applications
• LED flashlights and torches
• LED backlights
• White LED driver
SOT23
Typical application circuit
VCC 1
3 VOUT
GND 2
Top view
VIN
L1
ZXSC380
1
Vcc
Vout 3
GND
2
GND
LED1
Issue 1 - March 2007
© Zetex Semiconductors plc 2007
1
www.zetex.com
1 page  
ZXSC380
Device description
The ZXSC380 is non-synchronous PFM, DC-DC controller IC which, with a high performance
internal transistor, for a high efficiency boost converter for use in single cell applications. A block
diagram is shown in Figure 1.
V
CC
1
+V
REF
R1
+
-
R2 ISENSE
3
V
OUT
R
SENSE
2
GGNNDD
Figure 1 ZXSC380 Block diagram
The on chip comparator forces the driver circuit and therefore the internal switching transistor to
switch off when the voltage at ISENSE exceeds 20mV. This threshold is set by an internal reference
circuit and divider. The voltage at ISENSE is taken from a current sense resistor connected in series
with the emitter of the switching transistor. This resistor is chosen to give 20mV at ISENSE for an
emitter current of 80mA.
A monostable following the output of the comparator forces the turn-off time of the output stage
to be typically 2.2s. This ensures that there is sufficient time to discharge a significant proportion
of the energy stored in the inductor coil before the next On period.
With every On pulse the switching transistor is kept on until the voltage across the current-sense
resistor exceeds the threshold of the ISENSE input. The On-pulse length, and therefore the
switching frequency, is determined by the programmed peak current, the input voltage and the
input to output voltage differential. See applications section for details.
The Driver circuit supplies the internal switching transistor with a fixed drive current. To maximize
efficiency the internal transistor is switched quickly, typically being switched off within 30ns.
Issue 1 - March 2007
© Zetex Semiconductors plc 2007
5
www.zetex.com
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet ZXSC380.PDF ] | |
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