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PDF CAT4137 Data sheet ( Hoja de datos )
| Número de pieza | CAT4137 | |
| Descripción | CMOS Boost Converter - White LED Driver | |
| Fabricantes | Catalyst Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de CAT4137 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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CAT4137
CMOS Boost Converter - White LED Driver
Features
Product Description
• Drives up to 5 White LEDs from 3V
• Power Efficiency up to 87%
• Low Quiescent Ground Current 0.1mA
• Adjustable Output Current (up to 30mA)
• High Frequency 1MHz Operation
• “Zero” current shutdown mode
• Operates down to 2V (from two AA batteries)
• Soft start power-up
• Open LED low power mode
• Automatic shutdown at 1.9V (UVLO)
• Thermal shutdown protection
• Thin SOT23 5-Lead (1mm max height)
Applications
• LCD Backlighting
• Cellular Phones
• Handheld Devices
• Digital Cameras
The CAT4137 is a DC/DC step-up converter that
delivers a regulated output current. Operation at
a constant switching frequency of 1MHz allows
the device to be used with small value external
ceramic capacitors and inductor.
The device drives a string of white LEDs
connected in series and provides the regulated
current to control the LEDs with inherent uniform
brightness and matching. An external resistor R1
sets the output current and allows up to 30mA
current to be supported over a wide range of
input supply voltages from 2.2V to 5.5V, making
the device ideal for battery-powered applications.
LED dimming can be done by using a DC
voltage, a logic signal, or a pulse width
modulation (PWM) signal. The shutdown control
pin allows the device to be placed in power-down
mode with “zero” quiescent current.
Ordering Information
Part Number Package
CAT4137TS
CAT4137TD
TSOT23-5
TSOT23-5
Green
Quantity
per Reel
3000
3000
In addition to thermal protection and overload
current limiting, the device also enters a very low
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LW space critical applications.
LX
Pin Configuration
Top View
Typical Application Circuit
5-Lead Thin SOT23
1mm max height
L: Murata LQH32CN220
D: Central CMDSH2-3 (rated 30V)
© 2005 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1 of 14
Doc. 25093 , Rev. 00
1 page  
CAT4137
Typical Characteristics
VIN = 3.6V, CIN = 1.0uF, COUT = 0.22µF, L = 22µH, with 3 LEDs at 20mA, TAMB=25ºC, unless otherwise specified.
FB Pin Voltage vs. Temperature
304
302
300
298
3 LEDs at 20mA
296
Shutdown Voltage vs. Input Voltage
1.0
25°C
0.8
-40°C
0.6
85°C
0.4
294
-50
-25 0 25 50 75
TEMPERATURE [°C]
100
0.2
3.0
3.5 4.0 4.5
INPUT VOLTAGE [V]
5.0
Under Voltage Lock Out vs. Temperature
2.2
2.1
2.0
1.9
1.8
1.7
1.6
-50
-25 0 25 50 75
TEMPERATURE [°C]
100
Switching Waveforms (3 LEDs in Series)
Switching Frequency vs. Temperature
1.10
20mA per LED
1.05
1.00
0.95
0.90
-50
-25 0 25 50 75
TEMPERATURE [ºC]
100
Switching Waveforms (2 LEDs in Series)
© 2005 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5 of 14
Doc. 25093 , Rev. 00
5 Page 
Open LED Protection
In the event of an “Open LED” fault condition,
the CAT4137 will continue to boost the output
voltage with maximum power until the output
voltage reaches approximately 24V. Once the
output exceeds this level, internal circuitry
immediately places the device into a very low
power mode where the total input power
consumed is less than 10mW.
Open LED Protection
CAT4137
In low power mode, the input supply current
will typically drop to 2mA. An internal clamping
circuit will limit the subsequent output voltage to
approximately 29V. This operating mode
eliminates the need for any external protection
zener diode. This protection scheme also fully
protects the device against any malfunction in
the external Schottky diode (open-circuit).
Open LED Power-up Waveforms
Open LED Supply Current vs. VIN
2.5
2.0
1.5
1.0
2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE [V]
5.0
© 2005 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
11 of 14
Doc. 25093, Rev. 00
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet CAT4137.PDF ] | |
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