CAT4238 PDF даташит
Спецификация CAT4238 изготовлена «ON Semiconductor» и имеет функцию, называемую «High Efficiency 10 LED Boost Converter». |
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Детали детали
Номер произв | CAT4238 |
Описание | High Efficiency 10 LED Boost Converter |
Производители | ON Semiconductor |
логотип |
12 Pages
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CAT4238
High Efficiency 10 LED
Boost Converter
Description
The CAT4238 is a DC/DC step−up converter that delivers an
accurate constant current ideal for driving LEDs. Operation at a fixed
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 up to 5.5 V, making the device ideal for
battery−powered applications. The CAT4238 high−voltage output
stage is perfect for driving mid−size and large panel displays
containing up to ten white LEDs in series.
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 High Voltage LED Strings (38 V)
• Up to 87% Efficiency
• Low Quiescent Ground Current 0.6 mA
• Adjustable Output Current
• 1 MHz Fixed Frequency Low Noise Operation
• Soft Start “In−rush” Current Limiting
• Shutdown Current Less than 1 mA
• Open LED Overvoltage Protection
• Automatic Shutdown at 1.9 V (UVLO)
• Thermal Overload Protection
• Thin SOT23 5−lead (1 mm Max Height)
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
Applications
• GPS Navigation Systems
• Portable Media Players
• Handheld Devices, Digital Cameras
• Portable Game Machines
www.onsemi.com
5
1
TSOT−23
TD SUFFIX
CASE 419AE
PIN CONNECTIONS
1
SW VIN
GND
FB SHDN
(Top View)
MARKING DIAGRAM
MUYM
MU = Specific Device Code
Y = Production Year (Last Digit)
M = Production Month
(1−9 (Jan−Sep), O, N, D (Oct−Dec))
ORDERING INFORMATION
Device
CAT4238TD−GT3
Package
TSOT−23
(Pb−Free)
Green*
Shipping
3,000/
Tape & Reel
* Lead Finish NiPdAu
© Semiconductor Components Industries, LLC, 2016
April, 2016 − Rev. 5
1
Publication Order Number:
CAT4238/D
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CAT4238
VIN
C1
4.7 mF
OFF ON
L
47 mH
D VOUT
C2
SW 0.22 mF
VIN
CAT4238
SHDN
FB VFB = 300 mV
GND
R1
15 W
20 mA
L: Sumida CDC5D23B−470
D: Central CMDSH05−4
C2: Taiyo Yuden UMK212BJ224 (rated 50 V)
Figure 1. Typical Application Circuit
Table 1. ABSOLUTE MAXIMUM RATINGS
Parameters
Ratings
Units
VIN, FB voltage
SHDN voltage
−0.3 to +7
−0.3 to +7
V
V
SW voltage (Note 1)
up to 60
V
Storage Temperature Range
−65 to +160
_C
Junction Temperature Range
−40 to +150
_C
Lead Temperature
300 _C
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
1. The SW pin voltage is rated up to 39 V for external continuous DC voltage.
Table 2. RECOMMENDED OPERATING CONDITIONS
Parameters
Range
Units
VIN
SW pin voltage
up to 5.5
0 to 38
V
V
Ambient Temperature Range
−40 to +85
_C
Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond
the Recommended Operating Ranges limits may affect device reliability.
NOTE: Typical application circuit with external components is shown above.
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2
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CAT4238
Table 3. DC ELECTRICAL CHARACTERISTICS
(VIN = 3.6 V, ambient temperature of 25°C (over recommended operating conditions unless otherwise specified))
Symbol
Parameter
Test Conditions
Min Typ
Max Units
IQ Operating Current
ISD Shutdown Current
VFB FB Pin Voltage
IFB FB pin input leakage
ILED Programmed LED Current
VFB = 0.2 V
VFB = 0.4 V (not switching)
VSHDN = 0 V
10 LEDs with ILED = 20 mA
R1 = 10 W
R1 = 15 W
R1 = 20 W
0.6 1.5 mA
0.1 0.6
0.1 1 mA
285 300 315 mV
1 mA
28.5 30 31.5 mA
19 20 21
14.25 15 15.75
VIH SHDN Logic High
VIL SHDN Logic Low
Enable Threshold Level
Shutdown Threshold Level
0.8 1.5
0.4 0.7
V
FSW
DC
Switching Frequency
Maximum Duty Cycle
VIN = 3 V
0.8 1.0 1.3 MHz
92 %
ILIM
RSW
ILEAK
Switch Current Limit
Switch “On” Resistance
Switch Leakage Current
Thermal Shutdown
ISW = 100 mA
Switch Off, VSW = 5 V
350 450 600 mA
1.0 2.0
W
1 5 mA
150 °C
Thermal Hysteresis
20 °C
VUVLO
Undervoltage Lockout (UVLO) Threshold
1.9 V
VOV-SW
Overvoltage Detection Threshold
40 V
VOCL
Output Voltage Clamp
“Open LED” with VIN = 5 V
43 45 48
V
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
Pin Description
VIN is the supply input for the internal logic. The device is
compatible with supply voltages down to 2.8 V and up to
5.5 V. It is recommended that a small bypass ceramic
capacitor (4.7 mF) be placed between the VIN and GND pins
near the device. If the supply voltage drops below 1.9 V, the
device stops switching.
SHDN is the shutdown logic input. When the pin is tied to
a voltage lower than 0.4 V, the device is in shutdown mode,
drawing nearly zero current. When the pin is connected to a
voltage higher than 1.5 V, the device is enabled.
GND is the ground reference pin. This pin should be
connected directly to the ground place on the PCB.
SW pin is connected to the drain of the internal CMOS
power switch of the boost converter. The inductor and the
Schottky diode anode should be connected to the SW pin.
Traces going to the SW pin should be as short as possible
with minimum loop area. An over-voltage detection circuit
is connected to the SW pin. When the voltage reaches 40 V,
the device enters a low power operating mode preventing the
SW voltage from exceeding the maximum rating.
FB feedback pin is regulated at 0.3 V. A resistor connected
between the FB pin and ground sets the LED current
according to the formula:
0.3 V
ILED + R1
The lower LED cathode is connected to the FB pin.
Table 4. PIN DESCRIPTIONS
Pin #
Name
Function
1 SW Switch pin. This is the drain of the internal power switch.
2
GND
Ground pin. Connect the pin to the ground plane.
3 FB Feedback pin. Connect to the last LED cathode.
4
SHDN
Shutdown pin (Logic Low). Set high to enable the driver.
5 VIN Power Supply input.
www.onsemi.com
3
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