CAT4240_0711 [CATALYST]
6 Watt Boost LED Driver; 6瓦升压LED驱动器
| 型号： | CAT4240_0711 |
| 厂家： | 
CATALYST SEMICONDUCTOR |
| 描述： | 6 Watt Boost LED Driver |
| 文件： | 总14页 (文件大小：280K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
CAT4240
6 Watt Boost LED Driver
FEATURES
DESCRIPTION
Switch Current Limit 750mA
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 1MHz 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.
Drives High Voltage LED strings (38V)
Up to 94% Efficiency
Low Quiescent Ground Current 0.6mA
1MHz Fixed Frequency Low noise Operation
Soft start “in-rush” current limiting
Shutdown current less than 1μA
Open LED Overvoltage Protection
Automatic Shutdown at 1.9V (UVLO)
Thermal overload protection
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.
Thin SOT23 5-Lead (1mm max height)
APPLICATIONS
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 (1mm max height) 5-lead
thin SOT23 package for space critical applications.
GPS Navigation Systems
Portable Media Players
Handheld Devices, Digital Cameras
ORDERING INFORMATION
Quantity Package
per Reel Marking
Part Number
Package
TSOT23-5
Green*
CAT4240TD-GT3
3000 TG
* NiPdAu Plated Finish
For Ordering Information details, see page 13.
Typical Application Circuit
Pin Configuration
L1
D1
VL
VOUT
TSOT23 5-Lead
(1mm max height)
47µH
8V to
16V
C1
C2
4.7µF/16V
1µF/50V
(300mV)
SW
VIN
5V
1
2
5
4
SW
VIN
VIN
C3
CAT4240
GND
300mA
R2
1kΩ
1µF
SHDN
FB
3
SHDN
FB
R1
1Ω
GND
Top View
L1: Sumida CDRH6D28-470
D1: Central CMSH1-40 (rated 40V)
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. MD-5026 Rev. C
CAT4240
ABSOLUTE MAXIMUM RATINGS
Parameters
Ratings
Units
V
VIN, FB voltage
-0.3 to +7
-0.3 to +7
-0.3 to 60
-65 to +160
-40 to +150
300
¯¯¯¯¯
SHDN voltage
V
SW voltage
V
Storage Temperature Range
Junction Temperature Range
Lead Temperature
ºC
ºC
ºC
RECOMMENDED OPERATING CONDITIONS
Typical application circuit with external components are shown on page 1.
Parameters
Range
up to 5.5
0 to 38
Units
V
VIN
SW pin voltage
Ambient Temperature Range (1)
V
-40 to +85
ºC
DC ELECTRICAL CHARACTERISTICS
VIN = 3.6V, ambient temperature of 25ºC (over recommended operating conditions unless specified otherwise).
Typ
Symbol Parameter
Test Conditions
VFB = 0.2V
VFB = 0.4V (not switching)
Min
Max
Units
IQ
Operating Current
0.6
0.1
1.5
0.6
mA
ISD
VFB
IFB
Shutdown Current
0.1
1
315
1
µA
mV
µA
VS¯¯H¯D¯N¯ = 0V
FB Pin Voltage
6 LEDs with ILED = 75mA
285
300
FB pin input leakage
Programmed LED Current
ILED
R1 = 10Ω
R1 = 5Ω
28.5
30
60
31.5
mA
¯¯¯¯¯
SHDN Logic High
¯¯¯¯¯
SHDN Logic Low
VIH
VIL
Enable Threshold Level
Shutdown Threshold Level
0.8
0.7
1.5
1.3
V
V
0.4
0.8
FSW
DC
Switching Frequency
Maximum Duty Cycle
1.0
92
MHz
%
VIN = 3V
VIN = 3.6V
VIN = 5V
600
750
ILIM
Switch Current Limit
mA
RSW
ILEAK
Switch “On” Resistance
Switch Leakage Current
Thermal Shutdown
ISW = 100mA
1.0
2
2.0
5
Ω
Switch Off, VSW = 30V
µA
ºC
ºC
150
20
Thermal Hysteresis
Undervoltage Lockout (UVLO)
Threshold
VUVLO
1.9
V
VOV-SW Overvoltage Detection Threshold
VOCL Output Voltage Clamp
40
42
V
V
“Open LED”
Note:
(1) Thin SOT23-5 package thermal resistance θJA = 135°C/W when mounted on board over a ground plane.
Doc. No. MD-5026 Rev. C
2
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT4240
TYPICAL CHARACTERISTICS
VIN = 5V, VL = 13V, TAMB = 25ºC, typical application circuit unless otherwise specified.
Quiescent Current vs. VIN (Not Switching)
Quiescent Current vs. VIN (Switching)
200
2.0
1.5
1.0
0.5
0.0
VFB = 0.4V
150
100
50
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5 4.0
4.5 5.0
5.5
INPUT VOLTAGE [V]
INPUT VOLTAGE [V]
FB pin voltage vs. Temperature
FB Pin Voltage vs. Output Current
303
302
301
300
299
298
297
310
305
300
295
4 LEDs
290
-50
0
50
100
150
0
50
100
150
200
TEMPERATURE [ºC]
OUTPUT CURRENT [mA]
Switching Frequency vs. Supply Voltage
Switch ON Resistance vs. Input Voltage
1.2
2.0
1.5
1.0
0.5
0.0
1.1
1.0
0.9
0.8
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE [V]
INPUT VOLTAGE [V]
© Catalyst Semiconductor, Inc.
3
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
CAT4240
TYPICAL CHARACTERISTICS
VIN = 5V, VL = 13V, TAMB = 25ºC, typical application circuit unless otherwise specified.
LED Current vs. Input Voltage
LED Current Regulation
2.0
1.5
350
RSET = 1Ω
VOUT = 19.5V
300
1.0
0.5
250
0.0
200
-0.5
-1.0
-1.5
-2.0
RSET = 2Ω
VOUT = 18.8V
150
6 LEDs @ 150mA
100
8
9
10 11 12 13 14 15 16
8
9
10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
INDUCTOR VOLTAGE [V]
Efficiency vs. Load Current (6 LEDs)
Efficiency vs. Inductor Voltage (6 LEDs)
100
100
95
90
85
80
95
90
85
80
50
100 150 200 250 300
LED CURRENT [mA]
8
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
Power-up with 6 LEDs at 300mA
Switching Waveform
Doc. No. MD-5026 Rev. C
4
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT4240
TYPICAL CHARACTERISTICS
VIN = 5V, VL = 13V, TAMB = 25ºC, typical application circuit unless otherwise specified.
Maximum Output Current
Shutdown Voltage
1.0
0.8
0.6
0.4
0.2
500
400
300
200
100
-40°C
-25°C
VOUT = 20V
125°C
4.5
VOUT = 30V
85°C
3.5
3.0
4.0
5.0
8
9
10 11 12 13 14 15 16
INPUT VOLTAGE [V]
INDUCTOR VOLTAGE [V]
Switch Current Limit
1200
1100
1000
900
800
VOUT = 20V
700
2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE [V]
© Catalyst Semiconductor, Inc.
5
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
CAT4240
PIN DESCRIPTION
VIN is the supply input for the internal logic. The
device is compatible with supply voltages down to
2.8V and up to 5.5V. It is recommended that a small
bypass ceramic capacitor (4.7μF) be placed between
the VIN and GND pins near the device. If the supply
voltage drops below 1.9V, 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 40V, 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 0.4V, the device is in
shutdown mode, drawing nearly zero current. When
the pin is connected to a voltage higher than 1.5V, the
device is enabled.
FB feedback pin is regulated at 0.3V. 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.
ILED = 0.3V/R1
The lower LED cathode is connected to the FB pin.
Pin #
Name
SW
Function
1
2
3
4
5
Switch pin. This is the drain of the internal power switch.
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.
GND
FB
¯¯¯¯¯
SHDN
VIN
SIMPLIFIED BLOCK DIAGRAM
V
OUT
V
IN
SW
C1
C2
1MHz
Oscillator
Over Voltage
Protection
Ref
300mV
–
Driver
PWM
&
Logic
LED
Current
+
–
+
Thermal
Shutdown
& UVLO
V
IN
+
–
R
S
GND
SHDN
Current
Sense
FB
R1
Doc. No. MD-5026 Rev. C
6
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT4240
DEVICE OPERATION
The CAT4240 is a fixed frequency (1MHz), 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.
When the inductor is connected to a 9V supply or
higher, the CAT4240 can drive 6 LEDs in series at
300mA delivering a total power of 6 Watts into the
load. A separate 5V 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 40V, an internal protection circuit will become
active and place the device into a very low power safe
operating mode.
The on/off duty cycle of the power switch is internally
adjusted and controlled to maintain a constant
regulated voltage of 0.3V across the feedback resistor
connected to the feedback pin (FB). The value of the
resistor sets the LED current accordingly (0.3V/R1).
Thermal overload protection circuitry has been included
to prevent the device from operating at unsafe junction
temperatures above 150ºC. In the event of a thermal
overload condition the device will automatically
shutdown and wait till the junction temperatures cools
to 130ºC before normal operation is resumed.
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.
© Catalyst Semiconductor, Inc.
7
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
CAT4240
APPLICATION INFORMATION
External Component Selection
voltage at a given current. In order to achieve the best
efficiency, this forward voltage should be as low as
possible. The response time is also critical since the
driver is operating at 1MHz. Central Semiconductor
Schottky rectifier CMSH1-40 (1A rated) is
recommended for most applications.
Capacitors
The CAT4240 only requires small ceramic capacitors
of 4.7μF on the inductor input, 1µF on the VIN pin and
1µF on the output. Under normal condition, a 4.7µF
input capacitor is sufficient. For applications with
higher output power, a larger input capacitor of 10µF
may be appropriate. X5R and X7R capacitor types are
ideal due to their stability across temperature range.
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 47µH 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 800mA or
higher are recommended for most applications.
Sumida CDRH6D28-470 47µH inductor has a rated
current of 800mA and a series resistance (D.C.R.) of
176mΩ typical.
R1 = 0.3V/LED current
LED current (mA)
R1 (Ω)
20
25
15
12
10
3
30
100
300
Schottky Diode
1
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
Table 1. Resistor R1 and LED current
Doc. No. MD-5026 Rev. C
8
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT4240
OPEN LED PROTECTION
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 40V. 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 6mW (about
1.6mA input current with a 3.6V supply). The SW pin
clamps at a voltage below its maximum rating of
60V. There is no need to use an external zener
diode between Vout and the FB pin. A 50V rated C2
capacitor is required to prevent any overvoltage
damage in the open LED condition.
Open LED Disconnect and Reconnect
Open LED Protection without Zener
Open LED Disconnect
Schottky 100V
(Central CMSH1-100)
L
VL
47µH
13V
C1
VOUT
C2
4.7µF
SW
FB
1µF
VIN
5V
VIN
CAT4240
SHDN
GND
ON OFF
R1
3Ω
Open LED Supply Current vs. VIN
without Zener
Open LED Output Voltage vs. VIN
without Zener
60
55
50
45
40
5.0
4.0
3.0
2.0
1.0
VIN = 5V
0.0
8
9
10 11 12 13 14 15 16
8
9
10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
INDUCTOR VOLTAGE [V]
© Catalyst Semiconductor, Inc.
9
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
CAT4240
DIMMING CONTROL
Filtered PWM Signal
There are several methods available to control the
LED brightness.
A filtered PWM signal used as a variable DC voltage
can control the LED current. Figure 2 shows the
PWM control circuitry connected to the CAT4240 FB
pin. The PWM signal has a voltage swing of 0V to
2.5V. The LED current can be dimmed within a range
from 0mA to 20mA. The PWM signal frequency can
vary from very low frequency up to 100kHz.
¯¯¯¯¯
PWM signal on the SHDN Pin
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 1 shows a 1kHz
¯¯¯¯¯
signal with a 50% duty cycle applied to the SHDN pin.
VIN
SW
CAT4240
The recommended PWM frequency range is from
100Hz to 2kHz.
SHDN
GND
FB
VFB = 300mV
LED
Current
RA
3.73kΩ
2.5V
0V
PWM
Signal
VIN
RB
3.1kΩ
R2
1kΩ
R1
15Ω
C3
0.22µF
Figure 2. Circuit for Filtered PWM Signal
A PWM signal at 0V DC, or a 0% duty cycle, results
in a max LED current of about 22mA. A PWM signal
with a 93% duty cycle or more, results in an LED
current of 0mA.
25
20
15
10
5
Figure 1. Switching Waveform
¯¯¯¯¯
with 1kHz PWM on SHDN
0
0
10 20 30 40 50 60 70 80 90 100
PWM DUTY CYCLE [%]
Figure 3. Filtered PWM Dimming [0V to 2.5V]
Doc. No. MD-5026 Rev. C
10
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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 4 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 4 corresponds
to the current path when the CAT4240 internal switch
is closed. On Figure 5 is shown the current loop, when
the CAT4240 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 CAT4240 allows for direct connection
of the capacitors to ground. The resistor R1 must be
connected directly to the GND pin of the CAT4240
and not shared with the switching current loops and
any other components.
L
D
V
OUT
L
D
V
OUT
V
V
IN
IN
SW
SW
VIN
VIN
Switch
Closed
Switch
Open
CAT4240
CAT4240
FB
FB
SHDN
SHDN
R1
C
C
R1
C
C
2
1
2
1
GND
GND
Figure 4. Closed-switch Current Loop
Figure 5. Open-switch Current Loop
Figure 6. Recommended PCB Layout
© Catalyst Semiconductor, Inc.
11
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
CAT4240
PACKAGE OUTLINE DRAWING
TSOT-23 5-Lead (TD)(1)(2)
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
0.95TYP
0.40
E1
E
E
E1
e
L
0.30
0º
0.50
8º
L1
L2
θ
0.60 REF
0.25 BSC
TOP VIEW
A2 A
θ
L
b
c
A1
L2
L1
SIDE VIEW
END VIEW
For current Tape and Reel information, download the PDF file from:
http://www.catsemi.com/documents/tapeandreel.pdf.
Notes:
(1) All dimensions are in millimeters, angles in degrees.
(2) Complies with JEDEC standard MO-193.
Doc. No. MD-5026 Rev. C
12
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT4240
EXAMPLE OF ORDERING INFORMATION (1)
Prefix
Device #
Suffix
CAT
4240
TD
–
G
T3
Product Number
Lead Finish
G: NiPdAu
Tape & Reel
T: Tape & Reel
3: 3000/Reel
4240
Optional
Company ID
Package
TD: Thin SOT-23 (Lead-free, Halogen-free)
SERIES LED DRIVERS
Part Number
CAT4137
CAT4237
CAT4238
CAT4139
CAT4240
Description
CMOS Boost Converter – White LED Driver
High Voltage CMOS Boost White LED Driver
High Efficiency 10 LED Boost Converter
22V High Current Boost White LED Driver
6 Watt Boost LED Driver
Notes:
(1) All packages are RoHS-compliant (Lead-free, Halogen-free).
(2) The standard lead finish is NiPdAu.
(3) The device used in the above example is a CAT4240–GT3 (TSOT-23, NiPdAu, Tape & Reel).
(4) For additional package and temperature options, please contact your nearest Catalyst Semiconductor Sales office. -free, Halogen-free).
(5) Switch current limit, typical values.
© Catalyst Semiconductor, Inc.
13
Doc. No. MD-5026 Rev. C
Characteristics subject to change without notice
REVISION HISTORY
Date
Rev. Reason
05/31/2007
A
Initial Issue
Update Absolute Maximum Ratings
Update Package Outline Drawing
10/17/2007
11/06/07
B
Update Simplified Block Diagram
Update Device Operation text
Update Board Layout figure numbers
Update Series LED Drivers table
C
Copyrights, Trademarks and Patents
© Catalyst Semiconductor, Inc.
Trademarks and registered trademarks of Catalyst Semiconductor include each of the following:
Adaptive Analog™, Beyond Memory™, DPP™, EZDim™, LDD™, MiniPot™, Quad-Mode™ and Quantum Charge Programmable™
Catalyst Semiconductor has been issued U.S. and foreign patents and has patent applications pending that protect its products.
CATALYST SEMICONDUCTOR MAKES NO WARRANTY, REPRESENTATION OR GUARANTEE, EXPRESS OR IMPLIED, REGARDING THE SUITABILITY OF ITS
PRODUCTS FOR ANY PARTICULAR PURPOSE, NOR THAT THE USE OF ITS PRODUCTS WILL NOT INFRINGE ITS INTELLECTUAL PROPERTY RIGHTS OR THE
RIGHTS OF THIRD PARTIES WITH RESPECT TO ANY PARTICULAR USE OR APPLICATION AND SPECIFICALLY DISCLAIMS ANY AND ALL LIABILITY ARISING
OUT OF ANY SUCH USE OR APPLICATION, INCLUDING BUT NOT LIMITED TO, CONSEQUENTIAL OR INCIDENTAL DAMAGES.
Catalyst Semiconductor 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 Catalyst Semiconductor product could create a situation where personal
injury or death may occur.
Catalyst Semiconductor reserves the right to make changes to or discontinue any product or service described herein without notice. Products with data sheets labeled
"Advance Information" or "Preliminary" and other products described herein may not be in production or offered for sale.
Catalyst Semiconductor advises customers to obtain the current version of the relevant product information before placing orders. Circuit diagrams illustrate typical
semiconductor applications and may not be complete.
Catalyst Semiconductor, Inc.
Corporate Headquarters
2975 Stender Way
Santa Clara, CA 95054
Phone: 408.542.1000
Fax: 408.542.1200
www.catsemi.com
Document No: MD-5026
Revision:
C
Issue date:
11/06/07
相关型号：
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