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CAT32
CMOS White LED Driver
FEATURES
Low quiescent ground current (0.5mA typical) Power efficiency over 80% Compatible pinout with LT1932 Adjustable output current (up to 40mA) High frequency 1.2MHz operation Input voltage operation down to 2.0V Low resistance (0.5) high voltage power switch Drives up to 4 White LEDs in series Shutdown current less than 1A Load fault protection against open-circuits Low value external components Low profile (1mm) TSOT-23 6-lead and TDFN 8-pad (0.8mm) package
DESCRIPTION
The CAT32 is a DC/DC step up converter that delivers a regulated output current. Operation at a constant switching frequency of 1.2MHz allows the device to be used with very small value external inductor and ceramic capacitors. The CAT32 is targeted to drive multiple white lightemitting diodes (LEDs) connected in series and provides the necessary regulated current to control the brightness and the color purity. An external resistor RSET controls the output current level. LED currents of up to 40mA can be supported over a wide range of input supply voltages from 2V to 7V, 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 (1mm max height) 6-lead TSOT-23 package and in an 8-pad TDFN (0.8mm max height) package.
L1 6.8H D1
APPLICATION
Color LCD and keypad backlighting Cellular phones Handheld terminals Digital cameras PDAs/Games Portable MP3 players For Ordering Information details, see page 14.
TYPICAL APPLICATION CIRCUIT
VIN 2.7V to 4.2V
C1 4.7F
6 VIN CAT32
1 SW
PWM DIMMING CONTROL
5
SHDN RSET 4 RSET 1.50k
LED GND 2
3 15mA
C2 1F
C1: Taiyo Yuden JMK212BJ475 C2: Taiyo Yuden EMK212BJ105 D1: Zetez ZHCS400 L1: Sumida CLQ4D106R8 (Panasonic ELJEA6R8)
TSOT-23 Pin Numbers
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
ORDERING INFORMATION
Part Number CAT32TDI-T3 CAT32ZD4-GT3 CAT32TDI-GT3 Package TSOT23-6 TDFN-8 TSOT23-6 Reel Quantity 3000 3000 3000 Package Marking Code LL CCKV VF
PIN CONFIGURATION
TSOT-23 6-Lead Top View
SW GND LED 1 2 3 6 5 4 VIN SHDN RSET
TDFN 3 x 3mm
Power GROUND 1 VIN 2 SHDN 3 RSET 4 8 SW 7 NC 6 LED 5 GND
1mm maximum height JA = 250C/W [free air]
0.8mm maximum height (Top View)
PIN DESCRIPTION
Pin Number SOT23 1 2 3 4 5 6 -- Pin Number TDFN 8 5 6 4 3 2 1 Name SW GND LED RSET Function Switch pin. This is the drain of the internal power switch. For minimum EMI, minimize the trace area connected to this pin. Ground pin. Connect pin 2 to ground. LED (cathode) connection pin. RESET pin. A resistor connected from pin 4 to ground sets the LED current. This pin is also used to dim the LEDs. Shutdown pin. Input supply pin. This pin should be bypassed with a capacitor to ground. A 4.7F capacitor mounted close to the pin is recommended. Power Ground
SHDN
VIN Power Ground
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
ABSOLUTE MAXIMUM RATINGS
Parameter VIN, LED, voltage SHDN SW voltage RSET voltage Storage Temperature Range Junction Temperature Lead Soldering Temperature (10 secs) ESD Rating - Human Body Model
(1)
Rating 8 20 1 -65 to +150 125 300 2000
Unit V V V C C C V
RECOMMENDED OPERATING CONDITIONS
Parameter VIN Ambient Temperature Range Inductor L1 Input Capacitor C1 Output Capacitor C2 ILED with 1 to 4 LEDs in series Range 2 to 7 -40 to +85 6.8 20% typical 4.7 20% typical 1.0 20% typical 0 to 20 Unit V C H F F mA
Typical application circuit with external components is shown on page 1.
ELECTRICAL OPERATING CHARACTERISTICS
Over recommended operating conditions unless otherwise specified. TA = 25C, VIN = 2V and V = 1.2V. SHDN Symbol IQ IGND VLED ILED Parameter Quiescent Current Ground Current in Shutdown LED Pin Voltage LED Current Adjust Range RSET = 562 ILED Programmed LED Current RSET = 750 RSET = 1.5k RSET = 4.53k ILED VRSET LED Pin Current Temperature Coefficient RSET Pin Voltage Shutdown Pin Logic High Level Shutdown Pin Logic Low Level fSW ISWL RSW Boost Converter Frequency Switch Current Limit Switch Resistance Switch Leakage Current Efficiency VIN = 2V, ISW = 100mA VIN = 3V, ISW = 100mA Switch Off, VSW = 5V Components shown on Figure 1 0.8 400 1.2 550 0.7 0.5 0.01 83 ILED = 15mA RSET = 1.5k 0.85 0.25 1.6 780 1.2 0.9 5 Conditions VRSET = 0.2V V = 0V SHDN VIN < VOUT, ILED =15mA 5 33 25 12.5 38 30 15 5 -0.01 100 mA/C mV V V MHz mA A % Min Typ 0.5 0.05 120 Max 0.7 1 180 40 45 36 17.5 mA Unit mA A mV mA
Notes: (1) These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. (c) Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
TYPICAL CHARACTERISTICS
VIN = 3.6V, TAMB = 25C, CIN = 4.7F, COUT = 1F, L = 6.8H, unless otherwise specified.
600
Quiescent Current vs. Input Voltage
600
Quiescent Current vs. Temperature
QUIESCENT CURRENT [A]
QUIESCENT CURRENT [A]
500
VIN = 7V 500 VIN = 2V
400
400
300
300
200 2 3 4 5 6 7
200 -50 -25 0 25 50 75 100 125
TEMPERATURE [C]
INPUT VOLTAGE [V]
Switching Frequency vs. Input Voltage
2.00
Switching Frequency vs. Temperature
2.0
SWITCH FREQUENC Y [MHz]
1.60 1.20 0.80 0.40 0.00 2 3 4 5 6 7
SWITCH FREQUENC Y [MHz]
1.6 1.2 0.8 0.4 0.0 -50 -25 0 25 50 75 100 125
TEMPERATURE [C]
INPUT VOLTAGE [V]
LED Current vs. Input Voltage
35 30 25 20 15 10 5 0 2 3 4 5 6 7
RSET = 750
LED Current vs. Temperature
20
LED CURRENT [mA]
LED CURRENT [mA]
15 10 5 0 -50 -25 0 25 50 75 100 125
RSET = 1.13k RSET = 1.50k RSET = 2.26k
INPUT VOLTAGE [V]
TEMPERATURE [C]
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
TYPICAL CHARACTERISTICS
VIN = 3.6V, TAMB = 25C , CIN = 4.7F, COUT = 1F, L = 6.8H, unless otherwise specified. Switch Resistance vs. Input Voltage
1.0
1.0
Switch Resistance vs. Temperature
SWITCH RESISTANCE []
SWITCH RESISTANCE []
0.8 0.6 0.4 0.2 0.0 2 3 4 5 6
0.8 0.6 0.4 0.2 0.0 -50 -25 0 25 50 75 100 125
VIN = 3V
INPUT VOLTAGE [V]
TEMPERATURE [C]
LED Pin Voltage vs. LED current
300
VSW, IL, & VOUT Signal Waveforms
LED PIN VOLTAGE [mV]
250 200 150 100 50 0 0 8 16 24 32 40
LED CURRENT [mA]
85 80
Efficiency vs. Input Voltage
PWM on pin Waveform SHDN
EFFICIENCY [%]
75 70 65 60 2
4 LEDs at 15m A VOUT = 13V
3
4
5
6
INPUT VOLTAGE [V]
(c) Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
OPERATION
The CAT32 device is a high efficiency, constant frequency, current regulating boost converter. 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 100mV and the current through the external resistor will set the regulated current in the LEDs (from 5mA to 40mA) with a multiplication factor of 225. 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. PWM dimming operation can be achieved by switching the SHDN pin or by pulling the RSET pin higher than 0.1V.
BLOCK DIAGRAM
L1 VIN C1 Over Voltage Protection (22V) 1 SW C2 D1
1.2MHz Oscillator LED PWM & Logic Current Sense Amp 3 ILED
100mV
6 5
VIN SHDN IS CAT32 2 GND 4
Current Control 225x RSET RSET
ILED = 225 x IS
Figure 2. CAT32 Block Diagram
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
APPLICATION INFORMATION
INDUCTOR SELECTION AND EFFICIENCY Inductor vendors are shown below. Contact the manufacturer for detailed technical data and new product information. Table 1: Inductor Manufacturers Inductor ELJEA4R7 ELJEA6R8 LQH3C4R7M24, LQH32CN4R7M11 LQH3C100K24, LQH32CN100K11 LB2016B4R7 LB2016B100 CMD4D06-4R7 CMD4D06-6R8 CLQ4D10-4R7 CLQ4D10-6R8 L (H) 4.7 6.8 4.7 10 4.7 3.8 4.7 6.8 4.7 6.8 Maximum DCR (m) 180 250 260 300 250 350 216 296 162 195 Maximum Height (mm) 2.2 2.2 2.2 2.2 2.0 2.0 0.8 0.8 1.2 1.2 Sumida 847.956.0666 www.sumida.com Vendor Panasonic 714.373.7334 Murata 770.436.1300 Taiyo Yuden 408.573.4150 Web www.panasonic.com
www.murata.com
www.t-yuden.com
CAPACITOR 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 1.0F or 2.2F 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 10V ceramic capacitor is recommended when driving two LEDs. A 16V ceramic capacitor is recommended when driving 3 or 4 LEDs. Table 2: Ceramic Capacitor Manufacturers Supplier Taiyo Yuden Murata Kemet Phone 408.573.4150 814.237.1431 408.986.0424 Web www.t-yuden.com www.murata.com www.kemet.com Low profile ceramic capacitors with a 1mm 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 2.2F or 4.7F input capacitor is recommended. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information as new products and package options are introduced regularly.
(c) Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
DIODE SELECTION Schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for high efficiency applications. Table 3 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 0.4A or 0.5A diode will be sufficient for most designs. Table 3: Schottky Diode Suppliers Part MBR0520 MBR0530 s MBR0540 ZHCS400 Supplier ON Semiconductor www.onsemi.com 800.282.9855 Zetex two parallel strings of LEDs for greater light output, resulting in 30mA to 40mA (two strings of 15mA to 20mA) flowing into the LED pin. 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 5kHz to 40kHz PWM signal is used. PWM dimming with the CAT32 can be accomplished two different ways. The pin can be driven directly or a resistor SHDN 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.
LED CURRENT PROGRAMMING The LED current is programmed with a single resistor connected to the RSET pin The RSET pin is internally regulated to 100mV, which sets the current flowing out of this pin, ISET, equal to 100mV/RSET. The CAT32 regulates the current into the LED pin, ILED, to 225 times the value of ISET. For the best accuracy, a 1% or better resistor is recommended. Table 4 shows several typical 1% RSET values. Table 4: RSET Resistor Values ILED (mA) 40 30 25 20 15 10 5 RSET 562 750 909 1.13k 1.50k 2.26k 4.53k
RPWM = RSET x (
VMAX -1 ) 0.15 V
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 . If the RSET pin is used to provide PWM SHDN dimming, the approximate value of RPWM should be calculated (where VMAX is the "HIGH" value of the PWM signal): In addition to providing the widest dimming range, PWM 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 15mA or 20mA. 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 pin of the CAT32, the LEDs are turned off and SHDN 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.
For other LED current values, use the following equation to choose RSET.
R SET = 255 x
0.1V ILED
Most white LEDs are driven at maximum currents of 15mA to 20mA. Some higher power designs will use
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
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):
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 connection for the RSET resistor should be tied directly to the GND pin and not be shared with other components.
RMIN = 255 x
0.1V ILED(MIN)
RINCR determines how much LED current increases when the external NMOS switch is turned ON.
RINCR = 255 x
0.1V ILED(Increase )
LED DIMMING WITH A DC VOLTAGE
R ADJ = 225 x
VMAX - 0.1V ILED(MAX ) - ILEAD(MIN)
CAT32 SHDN 5
CAT32 RSET 4 RSET RPWM
CAT32 RSET 4 RSET 10k 0.1F RPWM PWM
CAT32 RSET 4 RSET RADJ
CAT32 RSET 4 RMIN RINCR Logic Signal
PWM
PWM
VDC
Figure 3. LED Dimming Circuits
(c) Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
TYPICAL APPLICATION CIRCUITS
The application diagrams below are shown for the TSOT-23 packages. Two LEDs with DC Level Dimming Control
L1 6.8H VIN 6 VIN CAT32 C1 4.7F 5 SHDN RSET 4 60.40k RSET 1.50k LED GND 2 3 15mA C2 2.2F 1 SW D1
2.5V DC DIMMING CONTROL
Three LEDs with DC Level Dimming Control
L1 6.8H VIN D1
85 80
Efficiency - Three LEDs
VIN = 4.2V VIN = 3.0V
EFFICIENCY [%]
6 VIN CAT32 C1 4.7F 5 SHDN RSET 4 60.40k RSET 1.50k
1 SW
75 70 65 60 0 5 10 15 20
LED GND 2
3 15mA
C2 1F
2.5V DC DIMMING CONTROL
LED CURRENT [mA]
Four LEDs with PWM Dimming Control
L1 6.8H VIN D1
Efficiency - Four LEDs
85 VIN = 4.2V 80
EFFICIENCY [%]
VIN = 3.0V
C1 4.7F
6 VIN CAT32
1 SW
75 70 65 60 0 5 10 15 20
PWM DIMMING CONTROL
5
SHDN RSET 4 RSET 1.50k
LED GND 2
3 15mA
C2 1F
LED CURRENT [mA]
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
PACKAGE OUTLINE DRAWINGS
TSOT-23 6-Lead (TD)
(1)(2)
D e
SYMBOL
MIN
NOM
MAX
A A1 A2 b c D
E1 E
1.00 0.01 0.80 0.30 0.12 0.15 2.90 BSC 2.80 BSC 1.60 BSC 0.95 TYP 0.30 0.40 0.60 REF 0.25 BSC 0 8 0.50 0.05 0.87 0.10 0.90 0.45 0.20
E E1 e L L1 L2
TOP VIEW
A2 A
b
A1 L1
L
c
L2
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. (c) Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. MD-5001 Rev. AD
CAT32
TDFN 8-Pad, 3 x 3mm (ZD4)
(1)(2)
D
A
e
b L
E
E2
PIN#1 ID
PIN#1 INDEX AREA
A1
D2
TOP VIEW
SIDE VIEW
BOTTOM VIEW
SYMBOL
MIN
NOM
MAX
A A1 A3 b D D2 E E2 e L
0.70 0.00 0.23 2.90 2.20 2.90 1.40 0.20
0.75 0.02 0.20 REF 0.30 3.00 -- 3.00 -- 0.65 TYP 0.30
0.80 0.05
A A3 A1
0.37 3.10 2.50 3.10 1.80 0.40
FRONT 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. (2) Complies with JEDEC standard MO-229.
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT32
EXAMPLE OF ORDERING INFORMATION 1
Prefix CAT
Device # 32
Suffix ZD4 - G T3
Product Number 32 Optional Company ID Package ZD4: TDFN TD: TSOT-23
Lead Finish G: NiPdAu
Tape & Reel T: Tape & Reel 3: 3,000/Reel
For Product Top Mark Codes, click here: http://www.catsemi.com/techsupport/producttopmark.asp
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 CAT32ZD4-GT3 (TDFN, NiPdAu, Tape & Reel, 3,000/Reel). (4) For additional package and temperature options, please contact your nearest Catalyst Semiconductor Sales office.
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Characteristics subject to change without notice
13
Doc. No. MD-5001 Rev. AD
REVISION HISTORY
Date 9-Oct-03 11-Feb-04 1-Nov-04 Rev. AA AB AC Reason Revised Typical Characteristics plots Revised Efficiency plots Added Green package designation Eliminated TDFN (3 x 4.9mm) package Update Package Outline Drawings Delete PbSn plated finish; add NiPdAu plated finish Add Example of Ordering Information Add MD- to document number.
23-May-08
AD
Copyrights, Trademarks and Patents (c) Catalyst Semiconductor, Inc. Trademarks and registered trademarks of Catalyst Semiconductor include each of the following: Adaptive AnalogTM, Beyond MemoryTM, DPPTM, EZDimTM, LDDTM, MiniPotTM, Quad-ModeTM and Quantum Charge ProgrammableTM 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-5001 Revision: AD Issue date: 05/23/2008

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