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CAT3637 6-Channel Programmable High Efficiency Quad-ModeTM LED Driver
FEATURES
High efficiency 1.33x charge pump Quad-Mode charge pump: 1x, 1.33x, 1.5x, 2x Drives 6 LEDs between 30mA and 0mA each 1-wire EZDimTM interface with 2mA step Power efficiency up to 92% Low noise input ripple in all modes "Zero" current shutdown mode Soft start and current limiting Short circuit protection Thermal shutdown protection Tiny 3mm x 3mm, 16-pad TQFN package
DESCRIPTION
The CAT3637 is a high efficiency Quad-Mode fractional charge pump that can drive up to six LEDs programmable by a 1-wire digital interface. The inclusion of a 1.33x fractional charge pump mode increases device efficiency by up to 10% over traditional 1.5x charge pumps with no added external capacitors. Low noise input ripple is achieved by operating at a constant switching frequency which allows the use of small external ceramic capacitors. The multi-fractional charge pump supports a wide range of input voltages from 2.5V to 5.5V. The EN/SET logic input functions as a chip enable and a digital programming interface for setting the current in the LED channels. The 1-wire pulse-programming interface supports 15 linear steps from zero current to 30mA fullbrightness in 2mA steps. The device is available in a tiny 16-pad TQFN 3 x 3mm package with a maximum height of 0.8mm. Catalyst Semiconductor's Quad-Mode 1.33x, charge pump switching architecture is patented. Package Marking JAAM
APPLICATIONS
LCD Display Backlight Cellular Phones Digital Still Cameras Handheld Devices
ORDERING INFORMATION
Part Number CAT3637HV3-GT2 Quantity per Reel 2000 (1)
For Ordering Information details, see page 13.
Note: (1) NiPdAu Plated Finish (RoHS-compliant) 16-lead TQFN 3mm x 3mm Package
PIN CONFIGURATION
(top view)
EN/SET
16 LED6 LED5 LED4 LED3 1 2 3 4 5 6 7 8
TYPICAL APPLICATION CIRCUIT
1F 1F
15
GND LED1
14
NC
13 12 C211 C2+ 10 C19 C1+
NC
VIN 2.5V to 5.5V CIN 1F C1VIN C1+ C2C2+ VOUT VOUT
CAT3637
1-Wire Programming
EN/SET GND
LED1 LED2 LED3 LED4 LED5 LED6
COUT 1F
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
LED2
VOUT
VIN
1
Doc. No. MD-5033 Rev. A
CAT3637 ABSOLUTE MAXIMUM RATINGS
Parameter VIN, LEDx, C1, C2 voltage VOUT Voltage EN/SET Voltage Storage Temperature Range Junction Temperature Range (1) Lead Temperature Rating 6 7 VIN + 0.7V -65 to +160 -40 to +150 300 Unit V V V C C C
RECOMMENDED OPERATING CONDITIONS
Parameter VIN Ambient Temperature Range(1) ILED per LED pin Total Output Current Range 2.5 to 5.5 -40 to +85 0 to 30 0 to 180 Unit V C mA mA
ELECTRICAL OPERATING CHARACTERISTICS
(over recommended operating conditions unless specified otherwise) VIN = 3.6V, EN = High, TAMB = 25C Symbol IQ IQSHDN ILED-ACC ILED-DEV Name Quiescent Current Shutdown Current LED Current Accuracy LED Channel Matching Conditions 1x mode, VIN = 4.2V 1.33 x mode, VIN = 3.3V 1.5x mode, VIN = 2.8V 2x mode, VIN = 2.5V VEN = 0V 2mA ILED 30mA ILED - ILEDAVG ILED 1x mode, IOUT = 120mA 1.33x mode, IOUT = 120mA 1.5x mode, IOUT = 120mA 2x mode, IOUT = 120mA 1.33x and 2x mode 1.5x mode VOUT < 0.5V Min Typ 1.5 2.8 3.7 3.8 3 1 0.5 3.5 3.5 6 0.8 1.1 80 150 VIN - Highest LED VF VOUT > 1V 1.3 0.4 150 20 2 400 120 450 100 Max Units mA mA mA mA A % % MHz MHz mA mV mV s mA k V V C C V
1
ROUT
Output Resistance (open loop)
FOSC ISC_MAX LEDTH VHYS TDF IIN_MAX REN/DIM VHI VLO TSD THYS VUVLO
Charge Pump Frequency Output short circuit Current Limit 1x to 1.33x or 1.33x to 1.5x or 1.5x to 2x Transition Thresholds at any LEDx pin 1.33x to 1x Transition Hysteresis Mode Transition Filter Delay Input Current Limit EN/DIM Pin * Internal Pull-down Resistor * Logic High Level * Logic Low Level Thermal Shutdown Thermal Hysteresis Undervoltage lockout (UVLO) threshold
0.6 0.8
1.1 1.4
Typical application circuit with external components is shown on page 1.
Notes: (1) Package thermal resistance is below 50C/W when mounted on FR4 board.
Doc. No. MD-5033 Rev. A
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(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3637 RECOMMENDED EN/SET TIMING
Symbol TLO THI TOFF TD Name EN/SET program low time EN/SET program high time EN/SET low time to shutdown LED current settling time
For 2.5 VIN 5.5V, over full ambient temperature range -40 to +85C. Conditions Min 0.2 0.2 1.5 10 Typ Max 100 Units s s ms s
THI EN/SET
TLO TD LED Current 28mA 30mA 6mA
TOFF
Shutdown
0mA
2mA 4mA
0mA
2mA
Shutdown
Figure 1. EN/SET One Wire Addressable Timing Diagram
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc. No. MD-5033 Rev. A
CAT3637 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 120mA (6 LEDs at 20mA), CIN = COUT = C1 = C2 = 1F, TAMB = 25C unless otherwise specified. Efficiency vs. Input Voltage
100 90 EFFICIENCY [%] 80 70 60 50 40 4.5 4.0 3.5 3.0 2.5 INPUT VOLTAGE [V] 2.0 VF = 3.3V 1.33x 1x
EFFICIENCY [%]
Efficiency vs. Li-Ion Voltage
100 VF = 3.3V VF = 3.0V
1.5x 2x
90 80 70 60 50 40
Traditional 1.5x Charge Pump 4.2 4.0 3.8 3.6 3.4 3.2 INPUT VOLTAGE [V] 3.0
LED Current Change vs. Input Voltage
LED CURRENT VARIATION [%] . 10 8 6 4 2 0 -2 -4 -6 -8 -10 5.5 5.0 4.5 4.0 3.5 3.0 INPUT VOLTAGE [V] 2.5 VF = 3.3V
LED Current Change vs. Temperature
LED CURRENT VARIATION [%] . 10 8 6 4 2 0 -2 -4 -6 -8 -10 -40 -20 0 20 40 60 TEMPERATURE [C] 80
Quiescent Current vs. Input Voltage
6.0 QUIESCENT CURRENT [mA] 5.0 4.0 3.0 2.0 1.0 0.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 INPUT VOLTAGE [V] VF = 3.3V
Doc. No. MD-5033 Rev. A
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CAT3637 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 120mA (6 LEDs at 20mA), CIN = COUT = C1 = C2 = 1F, TAMB = 25C unless otherwise specified. Switching Frequency vs. Temperature
SWITCHING FREQUENCY [MHz] 1.2 1.1 1.0 0.9 0.8 0.7 0.6 -40 -20 0 20 40 60 TEMPERATURE [C] 80 1.33x, 2x Mode 1.5x Mode
OUTPUT RESISTANCE [] .
Output Resistance vs. Input Voltage
10 VF = 3.3V 8 6 4 2 0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 INPUT VOLTAGE [V] 1.5x 2x 1.33x
1x
Power Up in 1x Mode
Power Up in 1.33x Mode
Power Up in 1.5x Mode
Power Up in 2x Mode
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Doc. No. MD-5033 Rev. A
CAT3637 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 120mA (6 LEDs at 20mA), CIN = COUT = C1 = C2 = 1F, TAMB = 25C unless otherwise specified. Power Up Delay (1x Mode) Power Down Delay (1x Mode)
Operating Waveforms in 1x Mode
Switching Waveforms in 1.33x Mode
Switching Waveforms in 1.5x Mode
Switching Waveforms in 2x Mode
Doc. No. MD-5033 Rev. A
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CAT3637 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, IOUT = 120mA (6 LEDs at 20mA), CIN = COUT = C1 = C2 = 1F, TAMB = 25C unless otherwise specified. Foldback Current Limit
4.0 OUTPUT VOLTAGE [V] 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 100 200 300 400 OUTPUT CURRENT [mA] 500 1x Mode
LED Brightness Levels
LED Settling Time
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Doc. No. MD-5033 Rev. A
CAT3637 PIN DESCRIPTION
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13/14 15 16 TAB Name LED6 LED5 LED4 LED3 LED2 LED1 VOUT VIN C1+ C1C2+ C2NC GND EN/SET TAB Function LED6 cathode terminal LED5 cathode terminal LED4 cathode terminal LED3 cathode terminal LED2 cathode terminal LED1 cathode terminal Charge pump output, connect to LED anodes Charge pump input, connect to battery or supply Bucket capacitor 1, positive terminal Bucket capacitor 1, negative terminal Bucket capacitor 2, positive terminal Bucket capacitor 2, negative terminal No connect Ground reference Device enable (active high) and 1 wire control input Connect to GND on the PCB
PIN FUNCTION
VIN is the supply pin for the charge pump. A small 1F ceramic bypass capacitor is required between the VIN pin and ground near the device. The operating input voltage range is from 2.5V to 5.5V. Whenever the input supply falls below the under-voltage threshold (2V) all the LED channels will be automatically disabled and the device register are reset to default values. EN/SET is the enable and one wire addressable control logic input for all LED channels. Guaranteed levels of logic high and logic low are set at 1.3V and 0.4V respectively. When EN/SET is initially taken high, the device becomes enabled and all LED currents remain at 0mA. To place the device into zero current mode, the EN/SET pin must be held low for more than 1.5ms. VOUT is the charge pump output that is connected to the LED anodes. A small 1F ceramic bypass capacitor is required between the VOUT pin and ground near the device. GND is the ground reference for the charge pump. The pin must be connected to the ground plane on the PCB. C1+, C1- are connected to each side of the ceramic bucket capacitor C1. C2+, C2- are connected to each side of the ceramic bucket capacitor C2. LED1 to LED6 provide the internal regulated current for each of the LED cathodes. These pins enter high-impedance zero current state whenever the device is placed in shutdown mode. TAB is the exposed pad underneath the package. For best thermal performance, the tab should be soldered to the PCB and connected to the ground plane.
Doc. No. MD-5033 Rev. A
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CAT3637 SIMPLIFIED BLOCK DIAGRAM
C1C1+ C2C2+
VIN
1x mode (LDO) 1.33x, 1.5x, 2x Charge Pump
VOUT
Mode Control EN/SET 100k Serial Interface Reference Voltage 0.8, 1.1MHz Oscillator LED1 LED2 LED3 LED4 LED5 LED6
Registers
Current Setting DAC
6 Current Regulators
GND
Figure 2. CAT3637 Functional Block Diagram
BASIC OPERATION
At power-up, the CAT3637 starts operating in 1x mode where the output will be approximately equal to the input supply voltage (less any internal voltage losses). If the output voltage is sufficient to regulate all LED currents, the device remains in 1x operating mode. If the output voltage is insufficient or falls to a level where the regulated current cannot be maintained, the device automatically switches into 1.33x mode (after a fixed delay time of about 120s). In 1.33x mode, the output voltage is approximately equal to 1.33 times the input supply voltage (less any internal voltage losses). If the output voltage is still insufficient or falls to a level where the regulated currents cannot be maintained, the device will automatically switch to the 1.5x mode (after a fixed delay time of about 400s). In 1.5x mode, the output is approximately equal to 1.5 times the input supply voltage (less any internal voltage losses). If the output voltage is still insufficient to drive the LEDs, it will automatically switch into 2x mode where the output is approximately equal to 2 times the input supply voltage (less any internal voltage losses). If the device detects a sufficient output voltage to drive all LED currents in 1x mode, it will revert back to 1x mode. This only applies for changing back to the 1x mode.
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc. No. MD-5033 Rev. A
CAT3637
LED Current Setting The current in each of the six LED channels is programmed through the 1-wire EN/SET digital control input. At the initial power-up and once the EN/SET is set high, the LED current remains at zero in all channels. On the first EN/SET pulse (positive edge), the current is set to 2mA in all channels. On each consecutive pulse, the current is incremented by 2mA. On the 15th pulse, the current is equal to the full scale of 30mA. On the following pulse (16th pulse), the current goes back to zero and the previous sequence can be repeated. The EN/SET pin can be pulsed at high frequency 15 times to decrement the current by 2mA or to program the current from 0mA to 30mA. The maximum EN/SET signal frequency for programming the LED current is 2.5MHz. To power-down the device and turn-off all current sources, the EN/SET input should be kept low for a duration TOFF of 1.5ms or more. The driver typically powers-down with a delay of about 1ms.
Figure 3. EN/SET One Wire Addressable Timing Diagram
THI EN/SET
TLO TD LED Current 28mA 30mA 6mA
TOFF
Shutdown
0mA
2mA 4mA
0mA
2mA
Shutdown
Figure 4. EN/SET Program Increasing / Decreasing LED Current by 2mA
Doc. No. MD-5033 Rev. A
10
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3637
Unused LED Channels For applications with 5 LEDs or less, unused LEDs can be disabled by connecting the LED pin directly to VOUT, as shown on Figure 4. If LED pin voltage is within 1V of VOUT, then the channel is switched off and a 200A test current is placed in the channel to sense when the channel moves below VOUT - 1V.
1F 1F
External Components The driver requires two external 1F ceramic capacitors for decoupling input, output, and for the charge pump. Both capacitors type X5R and X7R are recommended for the LED driver application. In all charge pump modes, the input current ripple is kept very low by design and an input bypass capacitor of 1F is sufficient. In 1x mode, the device operates in linear mode and does not introduce switching noise back onto the supply.
COUT 1F
VIN 2.5V to 5.5V CIN 1F
C1VIN
C1+
C2-
C2+ VOUT
VOUT
CAT3637
1-Wire Programming
EN/SET GND
LED1 LED2 LED3 LED4 LED5 LED6
Recommended Layout In charge pump mode, the driver switches internally at a high frequency. It is recommended to minimize trace length to all four capacitors. A ground plane should cover the area under the driver IC as well as the bypass capacitors. Short connection to ground on capacitors CIN and COUT can be implemented with the use of multiple via. A copper area matching the TQFN exposed pad (TAB) must be connected to the ground plane underneath. The use of multiple via improves the package heat dissipation.
Figure 5. Five LED Application
Protection Mode If an LED is disconnected, the output voltage VOUT automatically limits at about 5.5V. This is to prevent the output pin from exceeding its absolute maximum rating. If the die temperature exceeds +150C the driver will enter a thermal protection shutdown mode. When the device temperature drops by about 20C the device will resume normal operation. LED Selection LEDs with forward voltages (VF) ranging from 1.3V to 5.0V may be used with the CAT3637. Selecting LEDs with lower VF is recommended in order to improve the efficiency by keeping the driver in 1x mode longer as the battery voltage decreases.
Figure 6. Recommended Layout For example, if a white LED with a VF of 3.3V is selected over one with VF of 3.5V, the CAT3637 will stay in 1x mode for lower supply voltage of 0.2V. This helps improve the efficiency and extends battery life.
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc. No. MD-5033 Rev. A
CAT3637 PACKAGE OUTLINE DRAWINGS
TQFN 16-Pad 3 x 3mm (HV3) (1)(2)
D
A
e
b L
E
E2
PIN#1 ID
PIN#1 INDEX AREA TOP VIEW
A1 SIDE VIEW
D2 BOTTOM VIEW
SYMBOL
MIN
NOM
MAX
A A1 A3 b D D2 E E2 e L
0.70 0.00 0.18 2.90 1.40 2.90 1.40 0.30
0.75 0.02 0.20 REF 0.25 3.00 - 3.00 - 0.50 BSC 0.40
0.80 0.05
A
A1
A3 FRONT VIEW
0.30 3.10 1.80 3.10 1.80 0.50
For current Tape & 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.
Doc. No. MD-5033 Rev. A
12
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3637 EXAMPLE OF ORDERING INFORMATION (1)
Prefix CAT
Device # 3637
Suffix HV3 - G T2
Product Number 3637 Optional Company ID Package HV3: TQFN 3 x 3mm
Lead Finish G: NiPdAu
Tape & Reel T: Tape & Reel 2: 2000/Reel
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 CAT3637HV3-GT2 (TQFN, NiPdAu, Tape & Reel, 2000 pcs / Reel). (4) For additional package and temperature options, please contact your nearest Catalyst Semiconductor Sales office.
(c) Catalyst Semiconductor, Inc. Characteristics subject to change without notice
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Doc. No. MD-5033 Rev. A
REVISION HISTORY
Date 03/07/2008 Rev. A Reason Initial Issue
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-5033 Revision: A Issue date: 03/07/08

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