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CAT32
CMOS White LED Driver
FEATURES
s Low quiescent ground current (0.5mA typical) s Power efficiency over 80% s Compatible pinout with LT1932 s Adjustable output current (up to 40mA) s High frequency 1.2MHz operation s Input voltage operation down to 2.0V s Low resistance (0.5) high voltage
H
GEN FR ALO
EE
LE
s Drives up to 4 White LEDs in series s Shutdown current less than 1A
A D F R E ETM
s Load fault protection against open-circuits s Low value external components s Low profile (1mm) 6-lead SOT23 and TDFN
(0.8mm) package
power switch
APPLICATIONS
s Color LCD and keypad backlighting s Cellular phones s Handheld terminals s Digital cameras s PDAs/Games s Portable MP3 players
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 thin SOT23 package and in a TDFN (0.8mm max height) package.
D1
TYPICAL APPLICATION
VIN 2.7V to 4.2V
6 VIN
1 SW
PWM DIMMING CONTROL
CAT32
5 SHDN RSET 4 LED GND 2 3 15mA
SOT23 Pin Numbers
C1: Taiyo Yuden JMK212BJ475 C2: Taiyo Yuden EMK212BJ105 D1: Zetez ZHCS400 L1: Sumida CLQ4D106R8 (Panasonic ELJEA6R8)
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
(c) 2004 by Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc No. 5001, Rev. AC
CAT32
ORDERING INFORMATION
Part Number CAT32EKT-TE7 CAT32RD4-TE7 CAT32RD4 CAT32TDI-TE7 Package 6-lead, thin SOT23 8-pad TDFN (3x3mm) 8-pad TDFN (3x3mm) 6-lead thin SOT23, Lead Free Tube Quantity
--
Reel Quantity 3000 3500
--
Package Marking Code BD CCEM CCEM LL
--
120
--
3000
PIN CONFIGURATION
SW GND LED 1 2 3 CAT32 6 5 4 VIN SHDN RSET
Power 1 GROUND VIN 2 SHDN 3 RSET 4 8 SW 7 NC 6 LED 5 GND
6-Lead SOT-23 1mm maximum height
[Free Air]
(Top View) TDFN Package: 3mm x 3mm 0.8mm maximum height (RD4)
PIN DESCRIPTIONS
Pin Number SOT23 1 Pin Number TDFN 8 Name SW 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
2 3 4
5 6 4
GND LED RSET
5 6
3 2
SHDN VIN
--
1
Power Ground
Doc. No. 5001, Rev. AC
2
CAT32
ABSOLUTE MAXIMUM RATINGS
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. VIN , LED, SHDN Voltage ....................................... 8V SW Voltage ........................................................... 20V RSET Voltage ......................................................... 1V Junction Temperature ....................................... 125C Lead Soldering Temperature (10 secs) ............ 300C Storage Temperature .......................... -65C to 150C ESD Rating - Human Body Model .................... 2000V
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
ELECTRICAL SPECIFICATIONS
Over recommended operating conditions unless otherwise specified. TA = 25C, VIN = 2V and VSHDN = 1.2V.
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 VSHDN = 0V 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 Units mA A mV mA
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Doc No. 5001, Rev. AC
CAT32
TYPICAL CHARACTERISTICS
VIN=3.6V, TAMB=25C, CIN=4.7F, COUT=1F, L=6.8H, unless otherwise specified.
Quiescent Current vs. Input Voltage
600
Quiescent Current vs. Temperature
600
.
VIN = 7V 500
500
400
400
VIN = 2V
300
300
200 2 3 4 5 6 7
INPUT VOLTAGE [V]
200 -50 -25 0 25 50 75 100 125
Switching Frequency vs. Input Voltage
2.00 1.60 1.20 0.80 0.40 0.00 2 3 4 5 6 7 INPUT VOLTAGE [V]
Switching Frequency vs. Temperature
2.0
SWITCH FREQUENCY [MHz]
SWITCH FREQUENCY [MHz]
1.6 1.2 0.8 0.4 0.0 -50 -25 0 25 50 75 100 125
LED Current vs. Input Voltage
35 Rset = 750
LED Current vs. Temperature
20
LED CURRENT [mA]
30
LED CURRENT [mA]
6 7
25 20
15
Rset = 1.13k Rset = 1.5k
15 10 5 0 2 3
10
Rset = 2.26k
5
4 5 INPUT VOLTAGE [V]
0 -50 -25 0 25 50 75 100 125
Doc. No. 5001, Rev. AC
4
CAT32
TYPICAL CHARACTERISTICS
VIN=3.6V,TAMB=25C, CIN=4.7F, COUT=1F, L=6.8H, unless otherwise specified.
Switch Resistance vs. Input Voltage
SWITCH RESISTANCE [Ohm] .
1.0 0.8 0.6 0.4 0.2 0.0 2 3 4 5 6 INPUT VOLTAGE [V]
Switch Resistance vs. Temperature
SWITCH RESISTANCE [Ohm] . 1.0 0.8 0.6 0.4 0.2 0.0 -50 -25 0 25 50 75 100 125 VIN = 3V
LED Pin Voltage vs. LED current
300 250 200 150 100 50 0 0 8 16 24 32 LED CURRENT [mA] 40
Vsw, IL, & Vout Signal Waveforms
VIN = 3.7V with 15mA load through 4 LEDs
Efficiency vs. Input Voltage
85 EFFICIENCY (%) . 80 75 70 65 60 2 3 4 5 INPUT VOLTAGE [V] 6 4 LEDs at 15mA Vout =13V
PWM on SHDN pin Waveform
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Doc No. 5001, Rev. AC
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 D1 1
Vin
C1
C2
Over Voltage Protection (22V)
SW
1.2 MHz Oscillator
LED 3 ILED
PWM & Logic +
100mV 6 5 VIN SHDN Current Control
CAT32
Current Sense Amp
225x GND 2 IS 4 RSET RSET
Figure 2. CAT32 Block Diagram
Doc. No. 5001, Rev. AC
6
+ -
ILED = 225 x IS
SOT23 Pin Numbers
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 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 Sumida 847.956.0666 www.sumida.com Taiyo Yuden 408.573.4150 www.t-yuden.com 10 300 2.2 L (H) 4.7 6.8 4.7 Maximum DCR (m) 180 250 260 Maximum Height (mm) 2.2 2.2 2.2 Murata 770.436.1300 www.murata.com Vendor Panasonic 714.373.7334 www.panasonic.com Web
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.
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Doc No. 5001, Rev. AC
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 Table 3: Schottky Diode Suppliers Part MBR0520 MBR0530 MBR0540 ZHCS400 Supplier ON Semiconductor www.onsemi.com 800.282.9855 Zetex output voltage. The diode conducts current only when the power switch is turned off (typically less than onethird the time), so a 0.4A or 0.5A diode will be sufficient for most designs.
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 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 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.
For other LED current values, use the following equation to choose RSET.
0.1V RSET = 225 x ILED
Most white LEDs are driven at maximum currents of 15mA to 20mA. Some higher power designs will use 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.
Doc. No. 5001, Rev. AC
8
CAT32
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 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, the approximate value of RPWM should be calculated (where VMAX is the "HIGH" value of the PWM signal): V RPWM = RSET x MAX - 1 0.15V 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):
0.1V RMIN = 225 x ILED(MIN)
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 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.
RINCR determines how much LED current increases when the external NMOS switch is turned ON.
0.1V RINCR = 225 x ILED(Increase)
LED DIMMING WITH A DC VOLTAGE VMAX - 0.1V R ADJ = 225 x I LED(MAX ) -ILEAD(MIN)
CAT32 SHDN 5 PWM
CAT32 RSET 4 RPWM PWM RSET
CAT32 RSET 4 10k RPWM PWM RSET 0.1F
CAT32 RSET 4 RADJ VDC RSET
CAT32 RSET 4 RINCR LOGIC SIGNAL
RMIN
Figure 3: LED Dimming Circuits
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Doc No. 5001, Rev. AC
CAT32
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.
TYPICAL APPLICATION CIRCUITS
The application diagrams below are shown for the SOT23 packages. Two LEDs with DC Level Dimming Control:
D1 VIN 6 VIN 1 SW
CAT32
5 SHDN RSET 4 LED GND 2 3 15mA
2.5V DC DIMMING CONTROL
Three LEDs with DC Level Dimming Control:
D1 VIN 6 VIN 1 SW
Efficiency - Three LEDs
85 Vin = 4.2V
EFFICIENCY [%]
80 Vin = 3.0V 75 70 65 60 0 5 10 15 20
CAT32
5 SHDN RSET 4 LED GND 2 3 15mA
2.5V DC DIMMING CONTROL
LED CURRENT [mA]
Doc. No. 5001, Rev. AC
10
CAT32
Efficiency - Four LEDs
D1 VIN 6 VIN 1 SW
Four LEDs with PWM Dimming Control:
85
EFFICIENCY [%]
Vin = 4.2V
80
Vin = 3.0V
75 70 65 60 0 5 10 15 20
LED CURRENT [mA]
PWM DIMMING CONTROL
CAT32
5 SHDN RSET 4 LED GND 2 3 15mA
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Doc No. 5001, Rev. AC
CAT32
PACKAGE OUTLINES 6 LEAD SOT-23 (AA OPTION)
A N
3 D
4 e1 5 N/2 +1
aaa C 2X
H
D
B B
VIEW A-A SEE VIEW C
E/2 E1/2 3 4 E1 E
R1 R GAUGE PLANE L2
aaa C D 2X 1 e 5 B NX b ddd 2 N/2
SEATING C PLANE
L (L1) VIEW C
bbb C 2X N/2 TIPS
(b) b1
WITH METAL
M
CA BD
c
c1
BASE METAL
SECTION B - B
b5
8 5 e/2
A
7
X X=A &/or B
A
X X=A &/or B EVEN LEAD SIDES TOP VIEW
A2 NX A1
ccc C
ODD LEAD SIDES TOP VIEW
A
SEATING C PLANE
All Dimensions are in Millimeters
Min A A1 A2 c c1 D E E1 L L1 L2 R R1 0.10 0.10 0 0.30 -- 0.01 0.84 0.12 0.08 Nom -- 0.05 0.87 0.15 0.13 2.90BSC 2.80BSC 1.60BSC 0.40 0.60REF 0.25BSC -- -- 4 -- 0.25 8 ddd 0.20 0.50 Max 1.00 0.10 0.90 0.20 0.16 7 7 3,4 3,4 3,4 b b1 e e1 N Min 0.30 0.31 AA Nom -- 0.35 0.95BSC 1.90BSC 6 Max 0.45 0.39 Min 0.30 0.31 Notes aaa bbb ccc Tolerances of Form and Position 0.15 0.25 0.10 Variations 6 AB Nom -- 0.35 0.95BSC 1.90BSC 5 Tolerances of Form and Position 0.20 0.13 1,2 Max 0.45 0.39 Min 0.22 0.22 BA Nom -- 0.26 0.65BSC 1.95BSC 8 Max 0.36 0.30 Notes 7,8 Notes 1,2 1,2 1,2
4. 5. 6. 7. 8.
Notes: 1. Dimensions and tolerancing per ASME Y14.5M - 1994 2. Dimension are in mm. 1 4 10 12 3. Dimension D does not include mold flash, protrusions or gate burrs. Mold flash, protrusions or gate burrs shall not exceed 0.15mm per end. Dimension E1 does not include interlead flash or protrusion. Interlead flash or protrusion shall not exceed 0.15mm per side. D and E1 dimensions are determined at Datum H. The package top may be smaller than the package bottom. Dimensions D and E1 are determined at the outermost extremes of the plastic body exclusive of mold flash, the bar burrs, gate burrs and interlead flash, but including any mismatch between the top and bottom of the plastic body. D and E1 dimensions are determined at Datum H. Datums A & B to be determined at Datum H. Package varation "AB" is a 5 lead version of the 6 lead variation "AA" where lead #5 has been removed from the 6 lead "AA" variation. These dimensions apply to the flat section of the lead between 0.08mm and 0.15mm from the lead tip. Dimension "b" does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm total in excess of the "b" dimension at maximum material condition. The dambar cannot be located on the lower radius of the foot. Minimum space between protrusion and an adjacent lead shall not be less than 0.07mm.
Doc. No. 5001, Rev. AC
12
CAT32
TDFN 3X3 PACKAGE (RD4)
8
5
A B
0.75 + 0.05
3.00 + 0.10 (S)
2X
0.15 C
1 3.00 + 0.10 (S) PIN 1 INDEX AREA
4
2X 0.15 C
0.0 - 0.05 8
5
0.75 + 0.05
1.50 + 0.10
2.30 + 0.10 C0.35 PIN 1 ID
C 0.25 min.
1 0.30 + 0.07 (8x) 1.95 REF. (2x) NOTE: 1. ALL DIMENSION ARE IN mm. ANGLES IN DEGREES. 2. COPLANARITY SHALL NOT EXCEED 0.08 mm. 3. WARPAGE SHALL NOT EXCEED 0.10 mm. 4. PACKAGE LENGTH / PACKAGE WIDTH ARE CONSIDERED AS SPECIAL CHARACTERISTIC(S) 5. REFER JEDEC MO-229 / WEEC
0.30 + 0.10 (8x)
0.65 TYP. (6x)
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Doc No. 5001, Rev. AC
CAT32
REVISION HISTORY
Date 10/9/2003 2/11/2004 11/1/2004 Rev. AA AB AC Reason Revised Typical Characteristics plots Revised Efficiency plots Added Green package designation Eliminated TDFN (3x4.9mm) package
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Catalyst Semiconductor has been issued U.S. and foreign patents and has patent applications pending that protect its products. For a complete list of patents issued to Catalyst Semiconductor contact the Company's corporate office at 408.542.1000.
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Doc. No. 5001, Rev. AC
Publication #: Revison: Issue date: Type:
14
5001 AC 11/1/04 Preliminary

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