CAT4240 [ONSEMI]
6 Watt Boost LED Driver; 6瓦升压LED驱动器
| 型号： | CAT4240 |
| 厂家： | 
ONSEMI |
| 描述： | 6 Watt Boost LED Driver |
| 文件： | 总12页 (文件大小：186K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
CAT4240
6 Watt Boost LED Driver
Description
The CAT4240 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. The
CAT4240 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.
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5
1
TSOT−23
TD SUFFIX
CASE 419AE
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.
PIN CONNECTIONS
1
VIN
SW
GND
FB
Features
SHDN
• Switch Current Limit 750 mA
• Drives High Voltage LED Strings (38 V)
• Up to 94% Efficiency
• Low Quiescent Ground Current 0.6 mA
• 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
(Top View)
MARKING DIAGRAM
TGYM
TG = Specific Device Code
Y = Production Year (Last Digit)
M = Production Month (1−9, A, B, C)
• Thin SOT23 5−lead (1 mm Max Height)
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
ORDERING INFORMATION
Device
Package
Shipping
CAT4240TD−GT3
TSOT−23
(Pb−Free)
Green*
3,000/
Tape & Reel
Applications
• GPS Navigation Systems
• Portable Media Players
* NiPdAu Plated Finish
• Handheld Devices, Digital Cameras
L1
D1
V
L
VOUT
C2
47 mH
8 V to
16 V
C1
4.7 mF/16 V
1 μF/50 V
SW
FB
VIN
5 V
VIN
C3
1 μF
CAT4240
300 mA
R2
(300 mV)
SHDN
GND
1 kW
R1
1 W
L1: Sumida CDRH6D28−470
D1: Central CMSH1−40 (rated 40 V)
Figure 1. Typical Application Circuit
1
© Semiconductor Components Industries, LLC, 2010
Publication Order Number:
February, 2010 − Rev. 3
CAT4240/D
CAT4240
Table 1. ABSOLUTE MAXIMUM RATINGS
Parameters
Ratings
−0.3 to +7
−0.3 to +7
−0.3 to 60
−65 to +160
−40 to +150
300
Units
V
V
IN
, FB voltage
SHDN voltage
V
SW voltage
V
Storage Temperature Range
Junction Temperature Range
Lead Temperature
_C
_C
_C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
Table 2. RECOMMENDED OPERATING CONDITIONS
Parameters
Range
up to 5.5
0 to 38
Units
V
V
IN
SW pin voltage
V
Ambient Temperature Range (Note 1)
−40 to +85
_C
NOTE: Typical application circuit with external components is shown on page 1.
1. Thin SOT23−5 package thermal resistance q = 135°C/W when mounted on board over a ground plane.
JA
Table 3. DC ELECTRICAL CHARACTERISTICS
(V = 3.6 V, ambient temperature of 25°C (over recommended operating conditions unless otherwise specified))
IN
Symbol
Parameter
Operating Current
Test Conditions
Min
Typ
Max
Units
I
Q
V
FB
V
FB
= 0.2 V
= 0.4 V (not switching)
0.6
0.1
1.5
0.6
mA
I
Shutdown Current
FB Pin Voltage
V
= 0 V
0.1
1
315
1
mA
mV
mA
SD
SHDN
V
6 LEDs with I
= 75 mA
285
300
FB
LED
I
FB pin input leakage
Programmed LED Current
FB
I
R1 = 10 W
R1 = 5 W
28.5
30
60
31.5
mA
LED
V
SHDN Logic High
SHDN Logic Low
Enable Threshold Level
0.8
0.7
1.5
1.3
V
IH
IL
V
Shutdown Threshold Level
0.4
0.8
F
SW
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
1.0
92
MHz
%
DC
V
IN
= 3 V
I
V
IN
V
IN
= 3.6 V
= 5 V
600
750
mA
LIM
R
Switch “On” Resistance
I
= 100 mA
1.0
2
2.0
5
W
mA
°C
°C
V
SW
SW
I
Switch Leakage Current
Thermal Shutdown
Switch Off, V
= 30 V
SW
LEAK
150
20
1.9
40
42
Thermal Hysteresis
V
UVLO
Undervoltage Lockout (UVLO) Threshold
Overvoltage Detection Threshold
Output Voltage Clamp
V
V
OV-SW
V
OCL
“Open LED”
V
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CAT4240
TYPICAL CHARACTERISTICS
(V = 5 V, V = 13 V, T = 25°C, typical application circuit unless otherwise specified.)
IN
L
AMB
200
150
2.0
V
FB
= 0.4 V
1.5
1.0
100
50
0.5
0
3.0
3.5
4.0
4.5
5.0
5.5
150
5.5
3.0
3.5
4.0
4.5
5.0
5.5
200
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 2. Quiescent Current vs. VIN
(Not Switching)
Figure 3. Quiescent Current vs. VIN
(Switching)
310
305
300
303
302
301
300
299
295
290
298
297
4 LEDs
−50
0
50
100
0
50
100
150
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
Figure 4. FB Pin Voltage vs. Temperature
Figure 5. FB Pin Voltage vs. Output Current
1.2
2.0
1.5
1.0
1.1
1.0
0.9
0.8
0.5
0
3.0
3.5
4.0
4.5
5.0
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 6. Switching Frequency vs. Supply
Voltage
Figure 7. Switch ON Resistance vs. Input
Voltage
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CAT4240
TYPICAL CHARACTERISTICS
(V = 5 V, V = 13 V, T
= 25°C, typical application circuit unless otherwise specified.)
IN
L
AMB
350
300
2.0
1.5
1.0
0.5
0
RSET = 1 W
VOUT = 19.5 V
250
200
−0.5
−1.0
RSET = 2 W
VOUT = 18.8 V
150
100
−1.5
−2.0
6 LEDs @ 150 mA
8
9
10
11
12
13
14
15
16
8
9
10
11
12
13
14
15
16
INDUCTOR VOLTAGE (V)
INDUCTOR VOLTAGE (V)
Figure 8. LED Current vs. Input Voltage
Figure 9. LED Current Regulation
100
95
100
95
90
90
85
80
85
80
50
100
150
200
250
300
8
9
10
11
12
13
14
15
16
LED CURRENT (mA)
INDUCTOR VOLTAGE (V)
Figure 10. Efficiency vs. Load Current
(6 LEDs)
Figure 11. Efficiency vs. Inductor Voltage
(6 LEDs)
Figure 12. Power−up with 6 LEDs at 300 mA
Figure 13. Switching Waveform
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CAT4240
TYPICAL CHARACTERISTICS
(V = 5 V, V = 13 V, T
= 25°C, typical application circuit unless otherwise specified.)
IN
L
AMB
500
400
300
1.0
−40°C
0.8
0.6
VOUT = 20 V
−25°C
85°C
125°C
VOUT = 30 V
0.4
0.2
200
100
8
9
10
11
12
13
14
15
16
3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5
5.0
INDUCTOR VOLTAGE (V)
Figure 14. Maximum Output Current
Figure 15. Shutdown Voltage
1200
1100
1000
900
800
700
VOUT = 20 V
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Figure 16. Switch Current Limit
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CAT4240
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.
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.
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.
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:
GND is the ground reference pin. This pin should be
connected directly to the ground plane on the PCB.
0.3 V
R1
ILED
+
The lower LED cathode is connected to the FB pin.
Table 4. PIN DESCRIPTIONS
Pin #
Name
SW
Function
1
2
3
4
5
Switch pin. This is the drain of the internal power switch.
GND
FB
Ground pin. Connect the pin to the ground plane.
Feedback pin. Connect to the last LED cathode.
Shutdown pin (Logic Low). Set high to enable the driver.
Power Supply input.
SHDN
VIN
Simplified Block Diagram
V
IN
V
OUT
SW
C1
C2
1 MHz
Oscillator
Over Voltage
Protection
Ref
300 mV
–
Driver
PWM
&
Logic
LED
Current
+
–
+
Thermal
Shutdown
& UVLO
V
IN
+
–
R
S
SHDN
GND
Current
Sense
FB
R1
Figure 17. Simplified Block Diagram
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CAT4240
Device Operation
The CAT4240 is a fixed frequency (1 MHz), low noise,
inductive boost converter that provides a constant current
with excellent line and load regulation. The device uses a
high-voltage CMOS power switch between the SW pin and
ground to energize the inductor. When the switch is turned
off, the stored energy in the inductor is released into the load
via the Schottky diode.
The on/off duty cycle of the power switch is internally
adjusted and controlled to maintain a constant regulated
voltage of 0.3 V across the feedback resistor connected to the
feedback pin (FB). The value of the resistor sets the LED
When the inductor is connected to a 9 V supply or higher,
the CAT4240 can drive 6 LEDs in series at 300 mA
delivering a total power of 6 Watts into the load. A separate
5 V supply voltage is connected to the VIN pin.
In the event of an “Open LED” fault condition, where the
feedback control loop becomes open, the output voltage will
continue to increase. Once this voltage exceeds 40 V, an
internal protection circuit will become active and place the
device into a very low power safe operating mode.
Thermal overload protection circuitry has been included
to prevent the device from operating at unsafe junction
temperatures above 150°C. In the event of a thermal
overload condition the device will automatically shutdown
and wait till the junction temperatures cools to 130°C before
normal operation is resumed.
current accordingly (0.3 V/R ).
1
During the initial power−up stage, the duty cycle of the
internal power switch is limited to prevent excessive in−rush
currents and thereby provide a “soft−start” mode of
operation.
Application Information
External Component Selection
Capacitors
The CAT4240 only requires small ceramic capacitors of
4.7 mF on the inductor input, 1 mF on the VIN pin and 1 mF
on the output. Under normal condition, a 4.7 mF input
capacitor is sufficient. For applications with higher output
power, a larger input capacitor of 10 mF may be appropriate.
X5R and X7R capacitor types are ideal due to their stability
across temperature range.
forward voltage should be as low as possible. The response
time is also critical since the driver is operating at 1 MHz.
Central Semiconductor Schottky rectifier CMSH1−40 (1 A
rated) is recommended for most applications.
LED Current Setting
The LED current is set by the external resistor R1
connected between the feedback pin (FB) and ground. The
formula below gives the relationship between the resistor
and the current:
Inductor
A 47 mH inductor is recommended for most of the
CAT4240 applications. In cases where the efficiency is
critical, inductances with lower series resistance are
preferred. Inductors with current rating of 800 mA or higher
are recommended for most applications. Sumida
CDRH6D28−470 47 mH inductor has a rated current of
800 mA and a series resistance (D.C.R.) of 176 mW typical.
0.3 V
LED
R1 +
current
Table 5. RESISTOR R1 AND LED CURRENT
LED Current (mA)
R1 (W)
20
25
15
12
10
3
Schottky Diode
The current rating of the Schottky diode must exceed the
peak current flowing through it. The Schottky diode
performance is rated in terms of its forward voltage at a
given current. In order to achieve the best efficiency, this
30
100
300
1
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CAT4240
Open LED Protection
Schottky 100 V
In the event of an “Open LED” fault condition, the
CAT4240 will continue to boost the output voltage with
maximum power until the output voltage reaches
approximately 40 V. Once the output exceeds this level, the
internal circuitry immediately places the device into a very
low power mode where the total input power is limited to
about 6 mW (about 1.6 mA input current with a 3.6 V
supply). The SW pin clamps at a voltage below its maximum
rating of 60 V. There is no need to use an external zener diode
(Central CMSH1−100)
L
V
L
VOUT
47 mH
13 V
C2
C1
4.7 mF
1 mF
VIN
5 V
SW
CAT4240
VIN
ON
SHDN
GND
FB
OFF
between Vout and the FB pin. A 50 V rated C capacitor is
required to prevent any overvoltage damage in the open
LED condition.
2
R1
3 W
Figure 18. Open LED Protection without Zener
5.0
4.0
3.0
2.0
1.0
60
55
50
45
40
VIN = 5 V
0
8
9
10
11
12
13
14
15
16
8
9
10
11
12
13
14
15
16
INDUCTOR VOLTAGE (V)
INDUCTOR VOLTAGE (V)
Figure 19. Open LED Supply Current vs. VIN without
Zener
Figure 20. Open LED Output Voltage vs. VIN without
Zener
Figure 21. Open LED Disconnect and Reconnect
Figure 22. Open LED Disconnect
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CAT4240
Dimming Control
There are several methods available to control the LED
brightness.
VIN
SW
CAT4240
PWM Signal on the SHDN Pin
SHDN
GND
LED brightness dimming can be done by applying a PWM
signal to the SHDN input. The LED current is repetitively
turned on and off, so that the average current is proportional
to the duty cycle. A 100% duty cycle, with SHDN always
high, corresponds to the LEDs at nominal current. Figure 23
shows a 1 kHz signal with a 50% duty cycle applied to the
SHDN pin. The recommended PWM frequency range is
from 100 Hz to 2 kHz.
FB
V
PWM
= 300 mV
1 kW
Signal
2.5 V
FB
LED
Current
3.73 kW
3.1 kW
V
IN
0 V
R2
RA
C3
RB
R1
15 W
0.22 mF
Figure 24. Circuit for Filtered PWM Signal
A PWM signal at 0 V DC, or a 0% duty cycle, results in
a max LED current of about 22 mA. A PWM signal with a
93% duty cycle or more, results in an LED current of 0 mA.
25
20
15
10
5
0
Figure 23. Switching Waveform with 1 kHz PWM on
SHDN
Filtered PWM Signal
0
10 20 30 40 50 60
PWM DUTY CYCLE (%)
70 80 90 100
A filtered PWM signal used as a variable DC voltage can
control the LED current. Figure 24 shows the PWM control
circuitry connected to the CAT4240 FB pin. The PWM
signal has a voltage swing of 0 V to 2.5 V. The LED current
can be dimmed within a range from 0 mA to 20 mA. The
PWM signal frequency can vary from very low frequency up
to 100 kHz.
Figure 25. Filtered PWM Dimming (0 V to 2.5 V)
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CAT4240
Board Layout
The CAT4240 is a high−frequency switching regulator.
The traces that carry the high−frequency switching current
have to be carefully laid out on the board in order to
minimize EMI, ripple and noise in general. The thicker lines
on Figure 26 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 26 corresponds to the current path when the
CAT4240 internal switch is closed. On Figure 27 is shown
the current loop, when the CAT4240 switch is open. Both
loop areas should be as small as possible.
Capacitor C has to be placed as close as possible to the
1
V
IN
pin and GND. The capacitor C has to be connected
2
separately to the top LED anode. A ground plane under the
CAT4240 allows for direct connection of the capacitors to
ground. The resistor R must be connected directly to the
1
GND pin of the CAT4240 and not shared with the switching
current loops and any other components.
L
D
VOUT
L
D
VOUT
VIN
VIN
SW
SW
VIN
VIN
Switch
Open
Switch
Closed
CAT4240
CAT4240
FB
FB
SHDN
SHDN
C1
C2
R1
C1
C2
R1
GND
GND
Figure 26. Closed−switch Current Loop
Figure 27. Open−switch Current Loop
Figure 28. Recommended PCB Layout
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CAT4240
PACKAGE DIMENSIONS
TSOT−23, 5 LEAD
CASE 419AE−01
ISSUE O
SYMBOL
MIN
NOM
MAX
1.00
0.10
0.90
0.45
0.20
D
A
A1
A2
b
e
0.01
0.80
0.30
0.12
0.05
0.87
c
0.15
D
2.90 BSC
2.80 BSC
1.60 BSC
0.95 TYP
0.40
E1
E
E
E1
e
L
0.30
0.50
L1
L2
θ
0.60 REF
0.25 BSC
0º
8º
TOP VIEW
A2 A
q
L
b
c
A1
L2
L1
SIDE VIEW
END VIEW
Notes:
(1) All dimensions are in millimeters. Angles in degrees.
(2) Complies with JEDEC MO-193.
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CAT4240
Example of Ordering Information (Note 4)
Prefix
Device #
Suffix
CAT
4240
TD
− G
T3
Company ID
(Optional)
Product Number
Package
TD: Thin SOT−23
(Lead−free, Halogen−free)
Lead Finish
G: NiPdAu
Tape & Reel (Note 7)
T: Tape & Reel
3: 3,000 / Reel
4240
SERIES LED DRIVERS
Part Number
Description
CAT4137
CAT4237
CAT4238
CAT4139
CAT4240
CMOS Boost Converter − White LED Driver
High Voltage CMOS Boost White LED Driver
High Efficiency 10 LED Boost Converter
22 V High Current Boost White LED Driver
6 Watt Boost LED Driver
2. All packages are RoHS−compliant (Lead−free, Halogen−free).
3. The standard lead finish is NiPdAu.
4. The device used in the above example is a CAT4240TD−GT3 (TSOT−23, NiPdAu, Tape & Reel, 3,000/Reel).
5. For additional package and temperature options, please contact your nearest ON Semiconductor Sales office.
6. Switch current limit, typical values.
7. For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
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CAT4240/D
相关型号：
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