Catalyst CAT4240 0711 6 watt boost led driver Datasheet

CAT4240
6 Watt Boost LED Driver
FEATURES
„
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DESCRIPTION
Switch Current Limit 750mA
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
Thin SOT23 5-Lead (1mm max height)
APPLICATIONS
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.
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 (1mm max height) 5-lead
thin SOT23 package for space critical applications.
„ GPS Navigation Systems
„ Portable Media Players
„ Handheld Devices, Digital Cameras
ORDERING INFORMATION
Part Number
Package
CAT4240TD-GT3
TSOT23-5
Green*
Quantity Package
per Reel Marking
3000
TG
* NiPdAu Plated Finish
For Ordering Information details, see page 13.
Typical Application Circuit
Pin Configuration
SW
GND
FB
1
5
L1
VL
TSOT23 5-Lead
(1mm max height)
8V to
16V
VIN
VIN
5V
2
C1
C3
1µF
3
4
SHDN
D1
47µH
4.7µF/16V
C2
SW
VIN
CAT4240
SHDN
VOUT
FB
GND
1µF/50V
300mA
(300mV) R2
1kΩ
R1
1Ω
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
VIN, FB voltage
¯¯¯¯¯ voltage
SHDN
SW voltage
Storage Temperature Range
Junction Temperature Range
Lead Temperature
Ratings
-0.3 to +7
-0.3 to +7
-0.3 to 60
-65 to +160
-40 to +150
300
Units
V
V
V
ºC
ºC
ºC
RECOMMENDED OPERATING CONDITIONS
Typical application circuit with external components are shown on page 1.
Parameters
VIN
SW pin voltage
Ambient Temperature Range (1)
Range
up to 5.5
0 to 38
-40 to +85
Units
V
V
ºC
DC ELECTRICAL CHARACTERISTICS
VIN = 3.6V, ambient temperature of 25ºC (over recommended operating conditions unless specified otherwise).
Symbol Parameter
IQ
Operating Current
ISD
VFB
IFB
ILED
Shutdown Current
FB Pin Voltage
FB pin input leakage
Programmed LED Current
Test Conditions
VFB = 0.2V
VFB = 0.4V (not switching)
VSHDN
¯¯¯¯¯ = 0V
6 LEDs with ILED = 75mA
R1 = 10Ω
R1 = 5Ω
Enable Threshold Level
Shutdown Threshold Level
VIH
VIL
FSW
DC
¯¯¯¯¯ Logic High
SHDN
¯¯¯¯¯ Logic Low
SHDN
Switching Frequency
Maximum Duty Cycle
ILIM
Switch Current Limit
VIN = 3.6V
VIN = 5V
RSW
Switch “On” Resistance
ISW = 100mA
ILEAK
Switch Leakage Current
Switch Off, VSW = 30V
Min
285
28.5
Typ
0.6
0.1
Max
1.5
0.6
Units
mA
0.1
300
1
315
1
31.5
µA
mV
µA
mA
1.5
V
V
MHz
%
30
60
0.8
0.7
1.0
92
0.4
0.8
VIN = 3V
1.3
600
750
mA
1.0
2.0
Ω
2
5
µA
Thermal Shutdown
150
ºC
Thermal Hysteresis
20
ºC
VUVLO
Undervoltage Lockout (UVLO)
Threshold
1.9
V
VOV-SW
Overvoltage Detection Threshold
40
V
42
V
VOCL
Output Voltage Clamp
“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 (Switching)
2.0
200
QUIESCENT CURRENT [mA]
QUIESCENT CURRENT [μA] .
Quiescent Current vs. VIN (Not Switching)
VFB = 0.4V
150
100
1.5
1.0
0.5
0.0
50
3.0
3.5
4.0
4.5
5.0
3.0
5.5
FB pin voltage vs. Temperature
4.5
5.0
5.5
FB Pin Voltage vs. Output Current
310
FB PIN VOLTAGE [mV]
303
FB PIN VOLTAGE [mV]
4.0
INPUT VOLTAGE [V]
INPUT VOLTAGE [V]
302
301
300
299
298
297
305
300
295
4 LEDs
290
-50
0
50
100
150
0
TEMPERATURE [ºC]
50
100
150
200
OUTPUT CURRENT [mA]
Switching Frequency vs. Supply Voltage
Switch ON Resistance vs. Input Voltage
2.0
1.2
SWITCH RESISTANCE [Ω]
SWITCHING FREQUENCY [MHz]
3.5
1.1
1.0
0.9
1.5
1.0
0.5
0.0
0.8
3.0
3.5
4.0
4.5
5.0
3.0
5.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE [V]
INPUT VOLTAGE [V]
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
3.5
3
Doc. No. MD-5026 Rev. C
CAT4240
TYPICAL CHARACTERISTICS
VIN = 5V, VL = 13V, TAMB = 25ºC, typical application circuit unless otherwise specified.
LED Current vs. Input Voltage
LED CURRENT VARIATION [%] .
LED CURRENT [mA]
350
LED Current Regulation
RSET = 1Ω
VOUT = 19.5V
300
250
200
RSET = 2Ω
VOUT = 18.8V
150
100
8
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
8
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
Efficiency vs. Inductor Voltage (6 LEDs)
100
95
95
EFFICIENCY [%]
100
90
85
80
90
85
80
50
100 150 200 250
LED CURRENT [mA]
300
8
Power-up with 6 LEDs at 300mA
Doc. No. MD-5026 Rev. C
6 LEDs @ 150mA
-2.0
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
Efficiency vs. Load Current (6 LEDs)
EFFICIENCY [%]
2.0
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
Switching Waveform
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
400
SHUTDOWN VOLTAGE [V]
MAX OUTPUT CURRENT [mA]
500
VOUT = 20V
300
VOUT = 30V
200
-40°C
-25°C
0.8
0.6
125°C
0.4
85°C
0.2
100
8
3.0
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
Switch Current Limit
SW CURRENT LIMIT [mA]
1200
1100
1000
900
800
VOUT = 20V
700
2.5
3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE [V]
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5.5
5
Doc. No. MD-5026 Rev. C
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 overvoltage 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.
¯¯¯¯¯ is the shutdown logic input. When the pin is
SHDN
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
1
2
3
4
5
SW
GND
FB
¯¯¯¯¯
SHDN
VIN
Function
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.
SIMPLIFIED BLOCK DIAGRAM
VOUT
VIN
SW
C2
C1
1MHz
Oscillator
Ref
300mV
Over Voltage
Protection
–
+
PWM
&
Logic
+
–
LED
Current
RS
GND
Current
Sense
–
SHDN
Thermal
Shutdown
& UVLO
+
VIN
Driver
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.
Characteristics subject to change without notice
7
Doc. No. MD-5026 Rev. C
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)
20
25
30
100
300
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
Doc. No. MD-5026 Rev. C
R1 (Ω)
15
12
10
3
1
Table 1. Resistor R1 and LED current
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
13V
47µH
C1
VOUT
C2
4.7µF
SW
VIN
5V
VIN
ON OFF
SHDN
1µF
CAT4240
FB
R1
3Ω
Open LED Supply Current vs. VIN
without Zener
Open LED Output Voltage vs. VIN
without Zener
5.0
60
OUTPUT VOLTAGE [V]
INPUT CURRENT [mA]
GND
4.0
3.0
2.0
1.0
VIN = 5V
0.0
8
50
45
40
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
55
8
9
9 10 11 12 13 14 15 16
INDUCTOR VOLTAGE [V]
Doc. No. MD-5026 Rev. C
CAT4240
DIMMING CONTROL
Filtered PWM Signal
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.
There are several methods available to control the
LED brightness.
¯¯¯¯¯ Pin
PWM signal on the SHDN
LED brightness dimming can be done by applying a
¯¯¯¯¯ input. The LED current is
PWM signal to the SHDN
repetitively turned on and off, so that the average
current is proportional to the duty cycle. A 100% duty
¯¯¯¯¯ always high, corresponds to the
cycle, with SHDN
LEDs at nominal current. Figure 1 shows a 1kHz
¯¯¯¯¯ pin.
signal with a 50% duty cycle applied to the SHDN
The recommended PWM frequency range is from
100Hz to 2kHz.
VIN
SW
CAT4240
SHDN
GND
PWM 2.5V
Signal 0V
LED
Current
FB
RA
3.73kΩ
VFB = 300mV
VIN
RB
3.1kΩ
C3
0.22µF
R2
1kΩ
R1
15Ω
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
LED CURRENT [mA]
Figure 1. Switching Waveform
¯¯¯¯¯
with 1kHz PWM on SHDN
20
15
10
5
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.
L
D
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.
VOUT
L
VIN
D
VOUT
VIN
SW
SW
VIN
VIN
CAT4240
Switch
Closed
SHDN
CAT4240
FB
SHDN
C2
C1
R1
FB
C2
C1
GND
Switch
Open
R1
GND
Figure 4. Closed-switch Current Loop
Figure 5. Open-switch Current Loop
Figure 6. Recommended PCB Layout
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
11
Doc. No. MD-5026 Rev. C
CAT4240
PACKAGE OUTLINE DRAWING
TSOT-23 5-Lead (TD) (1)(2)
SYMBOL
D
MIN
NOM
A1
0.01
0.05
A2
0.80
0.87
b
0.30
c
0.12
MAX
A
e
1.00
D
E1
E
0.10
0.90
0.45
0.15
0.20
2.90 BSC
E
2.80 BSC
E1
1.60 BSC
e
0.95 TYP
L
0.30
L1
0.40
0.50
0.60 REF
L2
0.25 BSC
θ
0º
8º
TOP VIEW
A2 A
b
θ
L
A1
c
L1
SIDE VIEW
L2
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
Prefix
CAT
Device #
4240
(1)
Suffix
TD
Product Number
4240
–
G
Lead Finish
G: NiPdAu
T3
Tape & Reel
T: Tape & Reel
3: 3000/Reel
Optional
Company ID
Package
TD: Thin SOT-23 (Lead-free, Halogen-free)
SERIES LED DRIVERS
Part Number
Description
CAT4137
CMOS Boost Converter – White LED Driver
CAT4237
High Voltage CMOS Boost White LED Driver
CAT4238
High Efficiency 10 LED Boost Converter
CAT4139
22V High Current Boost White LED Driver
CAT4240
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.
Characteristics subject to change without notice
13
Doc. No. MD-5026 Rev. C
REVISION HISTORY
Date
Rev.
05/31/2007
A
10/17/2007
B
11/06/07
C
Reason
Initial Issue
Update Absolute Maximum Ratings
Update Package Outline Drawing
Update Simplified Block Diagram
Update Device Operation text
Update Board Layout figure numbers
Update Series LED Drivers table
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
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