|
|
PDF CAT4237 Data sheet ( Hoja de datos )
| Número de pieza | CAT4237 | |
| Descripción | High Voltage CMOS Boost White LED Driver | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de CAT4237 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
|
No Preview Available !
CAT4237
High Voltage CMOS Boost
White LED Driver
Description
The CAT4237 is a DC/DC step−up converter that delivers an
accurate constant current ideal for driving LEDs. Operation at a
constant switching frequency of 1 MHz allows the device to be used
with small value external ceramic capacitors and inductor. LEDs
connected in series are driven with a regulated current set by the
external resistor R1. LED currents up to 40 mA can be supported over
a wide range of input supply voltages from 2.8 V to 5.5 V, making the
device ideal for battery−powered applications. The CAT4237
high−voltage output stage is perfect for driving six, seven or eight
white LEDs in series with inherent current matching in LCD backlight
applications.
LED dimming can be done by using a DC voltage, a logic signal, or
a pulse width modulation (PWM) signal. The shutdown input pin
allows the device to be placed in power−down mode with “zero”
quiescent current.
In addition to thermal protection and overload current limiting, the
device also enters a very low power operating mode during “Open
LED” fault conditions. The device is housed in a low profile (1 mm
max height) 5−lead thin SOT23 package for space critical
applications.
Features
• Drives 6 to 8 White LEDs in Series from 3 V
• Up to 87% Efficiency
• Low Quiescent Ground Current 0.6 mA
• Adjustable Output Current (up to 40 mA)
• High Frequency 1 MHz Operation
• High Voltage Power Switch
• Shutdown Current Less than 1 mA
• Open LED Low Power Mode
• Automatic Shutdown at 1.9 V (UVLO)
• Thermal Shutdown Protection
• Thin SOT23 5−lead (1 mm Max Height)
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
Applications
• Color LCD and Keypad Backlighting
• Cellular Phones
• Handheld Devices
• Digital Cameras
• PDAs
• Portable Game Machine
http://onsemi.com
5
1
TSOT−23
TD SUFFIX
CASE 419AE
PIN CONNECTIONS
1
SW VIN
GND
FB SHDN
(Top View)
MARKING DIAGRAMS
LTYM
UDYM
LT = CAT4237TD−T3
UD = CAT4237TD−GT3
Y = Production Year (Last Digit)
M = Production Month (1−9, A, B, C)
ORDERING INFORMATION (Note 3)
Device
CAT4237TD−T3
(Note 1)
Package Shipping (Note 4)
TSOT−23
(Pb−Free)
3,000/
Tape & Reel
CAT4237TD−GT3 TSOT−23
(Note 2)
(Pb−Free)
3,000/
Tape & Reel
1. Matte−Tin Plated Finish (RoHS−compliant).
2. NiPdAu Plated Finish (RoHS−compliant)
3. For detailed information and a breakdown of
device nomenclature and numbering systems,
please see the ON Semiconductor Device No-
menclature document, TND310/D, available at
www.onsemi.com
4. For information on tape and reel specifications, in-
cluding part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifica-
tions Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2011
November, 2011 − Rev. 3
1
Publication Order Number:
CAT4237/D
1 page  
CAT4237
TYPICAL CHARACTERISTICS
(VIN = 3.6 V, CIN = 4.7 mF, COUT = 0.22 mF, L = 33 mH with 8 LEDs at 20 mA, TAMB = 25°C, unless otherwise specified.)
140 2.0
120
100 1.5
80
60
40
20
0
2.7
VFB = 0.4 V
(not switching)
3.0 3.3 3.6 3.9 4.2 4.5
INPUT VOLTAGE (V)
Figure 4. Quiescent Current vs. VIN
(Not Switching)
4.8
1.0
0.5
0
2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
Figure 5. Quiescent Current vs. VIN
(Switching)
315
310
8 LEDs at 20 mA
VOUT = 26 V
305
315
310
8 LEDs
305
5.0
300 300
295 295
290
285
2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8
INPUT VOLTAGE (V)
Figure 6. FB Pin Voltage vs. Supply Voltage
290
285
0 5 10 15 20 25 30
OUTPUT CURRENT (mA)
Figure 7. FB Pin Voltage vs. Output Current
1040
1020
1000
SW pin
20V/div
Inductor
Current
100mA/div
980
VOUT
AC coupled
200mV/div
960
2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8
INPUT VOLTAGE (V)
Figure 8. Switching Frequency vs. Supply
Voltage
0.5 msec/div
Figure 9. Switching Waveforms
http://onsemi.com
5
5 Page 
CAT4237
Board Layout
The CAT4237 is a high−frequency switching regulator.
The traces that carry the high−frequency switching current
have to be carefully layout on the board in order to minimize
EMI, ripple and noise in general. The thicker lines on
Figure 28 show the switching current path. All these traces
have to be short and wide enough to minimize the parasitic
inductance and resistance. The loop shown on Figure 28
corresponds to the current path when the CAT4237 internal
switch is closed. On Figure 29 is shown the current loop,
when the CAT4237 switch is open. Both loop areas should
be as small as possible.
Capacitor C1 has to be placed as close as possible to the
VIN pin and GND. The capacitor C2 has to be connected
separately to the top LED anode. A ground plane under the
CAT4237 allows for direct connection of the capacitors to
ground. The resistor R1 must be connected directly to the
GND pin of the CAT4237 and not shared with the switching
current loops and any other components.
Closed
Figure 28. Closed−switch Current Loop
Open
Figure 29. Open−switch Current Loop
http://onsemi.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet CAT4237.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| CAT4237 | High Voltage CMOS Boost White LED Driver |  Catalyst Semiconductor |
| CAT4237 | High Voltage CMOS Boost White LED Driver | ON Semiconductor |
| CAT4238 | High Efficiency 10 Led Boost Converter | Catalyst Semiconductor |
| CAT4238 | High Efficiency 10 LED Boost Converter | ON Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |