CAT32EKT [ONSEMI]
CMOS White LED Driver; CMOS白色LED驱动器
| 型号： | CAT32EKT |
| 厂家： | 
ONSEMI |
| 描述： | CMOS White LED Driver |
| 文件： | 总11页 (文件大小：172K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
CAT32
CMOS White LED Driver
Description
The CAT32 is a DC/DC step up converter that delivers a regulated
output current. Operation at a constant switching frequency of
1.2 MHz allows the device to be used with very small value external
inductor and ceramic capacitors.
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The CAT32 is targeted to drive multiple white light−emitting diodes
(LEDs) connected in series and provides the necessary regulated current
to control the brightness and the color purity. An external resistor R
SET
1
controls the output current level. LED currents of up to 40 mA can be
supported over a wide range of input supply voltages from 2 V to 7 V,
making the device ideal for battery−powered applications.
A high voltage output stage allows up to 4 White LEDs to be driven
in series. Series drive provides inherent current matching.
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 “near zero”
quiescent current.
In addition to overcurrent limiting protection, the device also
includes detection circuitry to ensure protection against open−circuit
load fault conditions.
The device is available in a low profile (1 mm max height) 6−lead
TSOT−23 package.
TSOT−23
TD SUFFIX
CASE 419AF
PIN CONNECTIONS
1
VIN
SW
GND
LED
SHDN
RSET
TSOT−23
1 mm Maximum Height
q
= 250°C/W (free air)
JA
(Top View)
Features
• Low Quiescent Ground Current (0.5 mA Typical)
• Power Efficiency Over 80%
• Compatible Pinout with LT1932
MARKING DIAGRAMS
• Adjustable Output Current (up to 40 mA)
• High Frequency 1.2 MHz Operation
• Input Voltage Operation down to 2.0 V
• Low Resistance (0.5 W) High Voltage Power Switch
• Drives up to 4 White LEDs in Series
• Shutdown Current Less than 1 mA
LLYM
VFYM
LL = CAT32TDI−T3
VF = CAT32TDI−GT3
Y = Production Year (Last Digit)
M = Production Month (1−9, A, B, C)
• Load Fault Protection Against Open−circuits
• Low Value External Components
ORDERING INFORMATION
• Low Profile (1 mm) TSOT−23 6−lead Package
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
Device
Package
Shipping
CAT32TDI−T3
TSOT−23
(Pb−Free)
3,000/
Tape & Reel
Applications
CAT32TDI−GT3
TSOT−23
(Pb−Free)
3,000/
Tape & Reel
• Color LCD and Keypad Backlighting
• Cellular Phones
• Handheld Terminals
• Digital Cameras
• PDAs/Games
• Portable MP3 Players
©
Semiconductor Components Industries, LLC, 2010
1
Publication Order Number:
March, 2010 − Rev. 4
CAT32/D
CAT32
Typical Application Circuit
D1
L
1
6.8 mH
VIN
2.7 V
to
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
4.2 V
C1
4.7 mF
1
6
SW
VIN
CAT32
PWM
3
5
C2
1 mF
DIMMING
SHDN
RSET
LED
CONTROL
GND
2
15 mA
4
R
SET
1.50 kW
TSOT−23 Pin Numbers
Figure 1. Li−Ion Driver for Four High−Brightness White LEDs
Table 1. PIN DESCRIPTION
Pin Number
SOT23
Pin Number
TDFN
Name
Function
1
8
SW
Switch pin. This is the drain of the internal power switch. For minimum EMI, min-
imize the trace area connected to this pin.
2
3
4
5
6
4
GND
LED
Ground pin. Connect pin 2 to ground.
LED (cathode) connection pin.
RSET
RESET pin. A resistor connected from pin 4 to ground sets the LED current. This
pin is also used to dim the LEDs.
5
6
3
2
SHDN
VIN
Shutdown pin.
Input supply pin. This pin should be bypassed with a capacitor to ground. A
4.7 mF capacitor mounted close to the pin is recommended.
−
1
Power
Ground
Power Ground
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2
CAT32
Table 2. ABSOLUTE MAXIMUM RATINGS
Parameter
Rating
Unit
V
V , LED, SHDN voltage
IN
8
SW voltage
20
1
V
RSET voltage
V
Storage Temperature Range
Junction Temperature
−65 to +150
125
°C
°C
°C
V
Lead Soldering Temperature (10 secs)
ESD Rating – Human Body Model
300
2000
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 3. RECOMMENDED OPERATING CONDITIONS
Parameter
Range
2 to 7
Unit
V
V
IN
Ambient Temperature Range
Inductor L1
−40 to +85
°C
6.8 20% typical
4.7 20% typical
1.0 20% typical
0 to 20
mH
mF
mF
mA
Input Capacitor C1
Output Capacitor C2
I
with 1 to 4 LEDs in series
LED
NOTE: Typical application circuit with external components is shown on page 2.
Table 4. ELECTRICAL OPERATING CHARACTERISTICS
(Over recommended operating conditions unless otherwise specified. T = 25°C, V = 2 V and V
= 1.2 V.)
A
IN
SHDN
Symbol
Parameter
Quiescent Current
Conditions
Min
Typ
Max
0.7
1
Unit
I
Q
V
RSET
= 0.2 V
0.5
0.05
120
mA
mA
I
Ground Current in Shutdown
LED Pin Voltage
V
SHDN
= 0 V
GND
V
V
IN
< V , I = 15 mA
OUT LED
180
40
mV
mA
mA
LED
LED
LED
I
I
LED Current Adjust Range
Programmed LED Current
5
33
R
R
= 562 W
38
30
45
SET
SET
SET
= 750 W
= 1.5 kW
25
36
R
12.5
15
17.5
R
= 4.53 kW
= 15 mA
= 1.5 kW
5
SET
I
LED Pin Current Temperature Coefficient
RSET Pin Voltage
I
−0.01
100
mA/°C
mV
V
LED
LED
V
RSET
R
SET
Shutdown Pin Logic High Level
Shutdown Pin Logic Low Level
Boost Converter Frequency
Switch Current Limit
0.85
0.25
1.6
780
1.2
0.9
5
V
f
0.8
1.2
550
0.7
MHz
mA
W
SW
I
400
SWL
R
Switch Resistance
V
= 2 V, I
= 3 V, I
= 100 mA
= 100 mA
SW
IN
SW
V
IN
0.5
SW
Switch Leakage Current
Efficiency
Switch Off, V
= 5 V
0.01
83
mA
SW
Components shown on Figure 1
%
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3
CAT32
TYPICAL CHARACTERISTICS
(V = 3.6 V, T
= 25°C, C = 4.7 mF, C
= 1 mF, L = 6.8 mH, unless otherwise specified.)
IN
AMB
IN
OUT
600
500
400
600
VIN = 7 V
500
VIN = 2 V
400
300
200
300
200
2
2
2
3
4
5
6
7
−50
−25
0
25
50
75
100
125
INPUT VOLTAGE (V)
TEMPERATURE (°C)
Figure 2. Quiescent Current vs. Input Voltage
Figure 3. Quiescent Current vs. Temperature
2.0
1.6
1.2
0.8
2.0
1.6
1.2
0.8
0.4
0
0.4
0
3
4
5
6
7
−50
−25
0
25
50
75
100
125
INPUT VOLTAGE (V)
TEMPERATURE (°C)
Figure 4. Switching Frequency vs. Input
Voltage
Figure 5. Switching Frequency vs.
Temperature
35
30
25
20
15
10
20
15
10
R
= 750 W
SET
R
SET
= 1.13 kW
R
R
= 1.50 kW
= 2.26 kW
SET
SET
5
0
5
0
3
4
5
6
7
−50
−25
0
25
50
75
100
125
INPUT VOLTAGE (V)
TEMPERATURE (°C)
Figure 6. LED Current vs. Input Voltage
Figure 7. LED Current vs. Temperature
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4
CAT32
TYPICAL CHARACTERISTICS
(V = 3.6 V, T
= 25°C, C = 4.7 mF, C
= 1 mF, L = 6.8 mH, unless otherwise specified.)
IN
AMB
IN
OUT
1.0
0.8
0.6
0.4
1.0
0.8
0.6
V
IN
= 3 V
0.4
0.2
0
0.2
0
2
0
2
3
4
5
6
−50
−25
0
25
50
75
100
125
INPUT VOLTAGE (V)
TEMPERATURE (°C)
Figure 8. Switch Resistance vs. Input Voltage
Figure 9. Switch Resistance vs. Temperature
Figure 11. VSW, IL, & VOUT Signal Waveforms
Figure 13. PWM on SHDN Pin Waveform
300
250
200
150
100
50
0
8
16
24
32
40
LED CURRENT (mA)
Figure 10. LED Pin Voltage vs. LED Current
85
80
75
70
4 LEDs at 15 mA
V
= 13 V
OUT
65
60
3
4
INPUT VOLTAGE (V)
5
6
Figure 12. Efficiency vs. Input Voltage
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5
CAT32
Operation
The CAT32 device is a high efficiency, constant
frequency, current regulating boost converter.
While maintaining LED current regulation, the CAT32
automatically adjusts the LED pin voltage to be as low as
possible. A low LED pin voltage ensures high efficiency.
Current through the internal power switch is continuously
monitored cycle−by−cycle. If the current limit is exceeded,
the switch is immediately turned off, protecting the device,
for the remainder of the cycle.
The device includes a switch and an internally
compensated loop for the regulation of the LED current.
Operation can be best understood by examining the block
diagram. The RSET pin is regulated at 100 mV and the
current through the external resistor will set the regulated
current in the LEDs (from 5 mA to 40 mA) with a
multiplication factor of 225.
PWM dimming operation can be achieved by switching
the SHDN pin or by pulling the RSET pin higher than 0.1 V.
Block Diagram
L
1
D
1
V
IN
C
2
1
C
1
SW
Over Voltage
Protection
1.2 MHz
(22 V)
Oscillator
LED
−
I
LED
3
PWM
& Logic
+
+
Current
Sense
Amp
−
100 mV
V
IN
6
5
Current
Control
I
= 225 x I
S
LED
SHDN
225x
I
S
CAT32
GND
RSET
2
4
R
SET
Figure 14. CAT32 Block Diagram
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6
CAT32
Application Information
Inductor Selection and Efficiency
Inductor vendors are shown below. Contact the manufacturer for detailed technical data and new product information.
Table 5. INDUCTOR MANUFACTURERS
Maximum
Height (mm)
Inductor
L (mH)
Maximum DCR (mW)
Vendor
Web
ELJEA4R7
4.7
180
250
2.2
2.2
Panasonic
714.373.7334
www.panasonic.com
ELJEA6R8
6.8
LQH3C4R7M24,
LQH32CN4R7M11
LQH3C100K24,
LQH32CN100K11
LB2016B4R7
4.7
10
260
300
2.2
2.2
Murata
770.436.1300
www.murata.com
www.t−yuden.com
www.sumida.com
4.7
3.8
4.7
6.8
4.7
6.8
250
350
216
296
162
195
2.0
2.0
0.8
0.8
1.2
1.2
Taiyo Yuden
408.573.4150
LB2016B100
CMD4D06−4R7
CMD4D06−6R8
CLQ4D10−4R7
CLQ4D10−6R8
Sumida
847.956.0666
Capacitor Selection
Diode Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple voltage.
The low ESR and small package options available with
multilayer ceramic capacitors make them excellent choices.
The X5R and X7R capacitor types are preferred because
they retain their capacitance over wider voltage and
temperature ranges than the Y5V or Z5U types. A 1.0 mF or
2.2 mF output capacitor is recommended for most
applications.
The voltage rating of the output capacitor C2 depends on
the number of LEDs driven in series. A 10 V ceramic
capacitor is recommended when driving two LEDs. A 16 V
ceramic capacitor is recommended when driving 3 or 4
LEDs.
Schottky diodes, with their low forward voltage drop and
fast switching speed, are the ideal choice for high efficiency
applications. Table 7 shows several different Schottky
diodes that work well with the CAT32. Make sure that the
diode has a voltage rating greater than the output voltage.
The diode conducts current only when the power switch is
turned off (typically less than one−third the time), so a 0.4 A
or 0.5 A diode will be sufficient for most designs.
Table 7. SCHOTTKY DIODE SUPPLIERS
Part
Supplier
MBR0520
MBR0530 s
MBR0540
ZHCS400
ON Semiconductor
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800.282.9855
Table 6. CERAMIC CAPACITOR MANUFACTURERS
Zetex
Supplier
Taiyo Yuden
Murata
Phone
Web
408.573.4150
814.237.1431
408.986.0424
www.t−yuden.com
www.murata.com
www.kemet.com
LED Current Programming
The LED current is programmed with a single resistor
connected to the RSET pin. The RSET pin is internally
regulated to 100 mV, which sets the current flowing out of
this pin, ISET, equal to 100 mV/RSET. The CAT32 regulates
Kemet
Low profile ceramic capacitors with a 1 mm maximum
height/thickness are available for designs height
requirements. Ceramic capacitors also make a good choice
for the input capacitor, which should be mounted as close as
possible to the CAT32. A 2.2 mF or 4.7 mF input capacitor is
recommended. Table 6 shows a list of several ceramic
capacitor manufacturers. Consult the manufacturers for
detailed information as new products and package options
are introduced regularly.
the current into the LED pin, I
, to 225 times the value of
LED
I
. For the best accuracy, a 1% or better resistor is
SET
recommended. Table 8 shows several typical 1% R
values.
SET
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7
CAT32
In addition to providing the widest dimming range, PWM
Table 8. RSET RESISTOR VALUES
brightness control also ensures the “purest” white LED color
over the entire dimming range. The true color of a white
LED changes with operating current, and is the “purest”
white at a specific forward current, usually 15 mA or
20 mA. If the LED current is less than or more than this
value, the emitted light becomes more blue. Applications
involving color LCDs can find the blue tint objectionable.
When a PWM control signal is used to drive the SHDN pin
of the CAT32, the LEDs are turned off and on at the PWM
frequency. The current through them alternates between full
current and zero current, so the average current changes with
duty cycle. This ensures that when the LEDs are on, they can
be driven at the appropriate current to give the purest white
light. LED brightness varies linearly with the PWM duty
cycle.
I
(mA)
R
SET
LED
40
562 W
750 W
30
25
20
15
10
5
909 W
1.13 kW
1.50 kW
2.26 kW
4.53 kW
For other LED current values, use the following equation
to choose R
.
SET
0.1 V
ILED
R
SET + 255
Most white LEDs are driven at maximum currents of
15 mA to 20 mA. Some higher power designs will use two
parallel strings of LEDs for greater light output, resulting in
30 mA to 40 mA (two strings of 15 mA to 20 mA) flowing
into the LED pin.
LED Dimming with a Logic Signal
For applications that need to adjust the LED brightness in
discrete steps, a logic signal can be used. RMIN sets the
minimum LED current value (when the NMOS is OFF):
0.1 V
ILED(MIN)
R
MIN + 255
LED Dimming with PWM Signal
PWM brightness control provides the widest dimming
range (greater than 20:1). By turning the LEDs ON and OFF
using the control signal the LEDs operate at either zero or
full current, but their average current changes with the PWM
signal duty cycle. Typically, a 5 kHz to 40 kHz PWM signal
is used. PWM dimming with the CAT32 can be
accomplished two different ways.
R
determines how much LED current increases when
INCR
the external NMOS switch is turned ON.
0.1 V
R
INCR + 255
ILED(Increase)
LED Dimming with a DC Voltage
The SHDN pin can be driven directly or a resistor can be
added to drive the RSET pin. If the SHDN pin is used,
increasing the duty cycle will increase the LED brightness.
Using this method, the LEDs can be dimmed and turned off
completely using the same control signal. A 0% duty cycle
signal will turn off the CAT32, reducing the total quiescent
current to near zero.
If the RSET pin is used, increasing the duty cycle will
decrease the brightness. Using this method, the LEDs are
dimmed using RSET and turned off completely using
SHDN. If the RSET pin is used to provide PWM dimming,
V
MAX * 0.1 V
R
ADJ + 225
I
LED(MAX) * ILEAD(MIN)
PCB Layout Guidelines
The CAT32 is a high−frequency switching regulator and
therefore proper PCB board layout and component
placement can minimize noise and radiation and increase
efficiency. To maximize efficiency, the CAT32 design has
fast switch rise and fall times. To prevent radiation and high
frequency resonance problems minimize the length and area
of all traces connected to the SW pin and use a ground plane
under the switching regulator.
The switch, schottky output diode and output capacitor
signal path should be kept as short as possible. The ground
resistor should be tied directly to the
GND pin and not be shared with other components.
the approximate value of R
should be calculated (where
PWM
V
MAX
is the “HIGH” value of the PWM signal):
VMAX
0.15 V
ǒ Ǔ
R
PWM + RSET
* 1
connection for the R
SET
CAT32
CAT32
CAT32
CAT32
CAT32
RSET
4
SHDN
5
RSET
4
RSET
4
RSET
4
R
PWM
PWM
PWM
V
DC
PWM
R
ADJ
R
10 kW
R
PWM
Logic
Signal
INCR
R
R
R
R
SET
MIN
SET
SET
0.1 mF
Figure 15. LED Dimming Circuits
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8
CAT32
TYPICAL APPLICATION CIRCUITS
(The application diagrams below are shown for the TSOT−23 packages.)
D1
L
1
6.8 mH
VIN
6
1
SW
VIN
CAT32
C1
4.7 mF
C2
2.2 mF
5
3
SHDN
LED
GND
2
RSET
4
15 mA
2.5 V DC 60.40 kW
DIMMING
CONTROL
R
SET
1.50 kW
Figure 16. Two LEDs with DC Level Dimming Control
D1
L
1
6.8 mH
VIN
85
V
IN
= 4.2 V
6
1
V
IN
= 3.0 V
VIN
SW
80
75
70
CAT32
C2
C1
4.7 mF
5
3
SHDN
LED
1 mF
GND
2
RSET
4
15 mA
60.40 kW
2.5 V DC
DIMMING
CONTROL
65
60
R
SET
1.50 kW
0
5
10
LED CURRENT (mA)
15
20
Figure 17. Three LEDs with DC Level Dimming Control
Figure 18. Efficiency − Three LEDs
D1
L
6.8 mH
1
VIN
85
80
75
70
V
IN
= 4.2 V
V
C1
4.7 mF
= 3.0 V
IN
6
1
SW
VIN
CAT32
PWM
C2
5
3
DIMMING
CONTROL
SHDN
RSET
4
LED
1 mF
GND
2
15 mA
65
60
R
SET
1.50 kW
0
5
10
15
20
LED CURRENT (mA)
Figure 19. Four LEDs with PWM Dimming Control
Figure 20. Efficiency − Four LEDs
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CAT32
PACKAGE DIMENSIONS
TSOT−23, 6 LEAD
CASE 419AF−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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10
CAT32
Example of Ordering Information (Note 3)
Prefix
Device #
Suffix
CAT
32
TD
I
− G
T3
Company ID
(Optional)
Product Number
Package
TD: TSOT−23
Temperature Range
I = Industrial
Lead Finish
G: NiPdAu
Tape & Reel (Note 5)
T: Tape & Reel
32
(−40°C to +85°C)
3: 3,000 / Reel
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 CAT32TDI−GT3 (TSOT−23, Industrial Temperature Range, NiPdAu, Tape & Reel, 3,000 / Reel).
4. For additional package and temperature options, please contact your nearest ON Semiconductor Sales office.
5. 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
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CAT32/D
相关型号：
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