CAT3626 6-Channel LED Driver with I2C Interface FEATURES PRODUCT DESCRIPTION Drives 6 LED channels Independent current on 3 pairs of LEDs I2C serial interface programming Adjustable current to 32mA in 0.5mA step Power efficiency up to 91% Fractional pump 1x/1.5x Low noise input ripple Fixed High Frequency Operation 1MHz “Zero” Current Shutdown Mode Soft start and current limiting Short circuit protection Thermal shutdown protection The CAT3626 is a high efficiency 1x/1.5x fractional charge pump with programmable dimming current in six LED channels. To ensure uniform brightness in LCD backlight applications, each LED channel delivers an accurate regulated current. Low noise and input ripple is achieved by operating at a constant switching frequency of 1MHz which allows the use of small external ceramic capacitors. The 1x/1.5x fractional charge pump supports a wide range of input voltages from 3V to 5.5V with efficiency up to 91%, and is ideal for Li-Ion battery powered devices. APPLICATION The LED channels are configured into three independent pairs, each containing 2 matched channels. Each pair can be separately programmed from zero to 32mA, in 0.5mA resolution steps, using the I2C serial interface. Any individual channel can be disabled while others remain active. When the enable input (EN) is low, the device is in shutdown mode drawing zero current. RGB LEDs LCD and keypad Backlighting Cellular Phones, PDAs Digital Cameras ORDERING INFORMATION Part Number Package Quantity Package per Reel Marking CAT3626HS4-T2 Thin QFN-16 2000 C626 CAT3626HV4-T2 Thin QFN-16 2000 G626 Green* The device is available in a 16-lead thin QFN package with a max height of 0.8mm. Note *: Matte Tin Lead Finish PIN CONFIGURATION TYPICAL APPLICATION CIRCUIT QFN 16-lead 4x4mm (Top View) 2 I C is a trademark of Philips Electronics N.V. © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 1 Doc. No. 3022 Rev. A CAT3626 ABSOLUTE MAXIMUM RATINGS Parameter VIN, LEDxx voltage VOUT, C1±, C2± voltage EN, SDA, SCL voltage Storage Temperature Range Junction Temperature Range Lead Temperature Rating 6 7 VIN + 0.7V -65 to +160 -40 to +125 300 Unit V V V ºC ºC ºC RECOMMENDED OPERATING CONDITIONS Parameter VIN Ambient Temperature Range LED forward voltage ILED per LED pin Range 3 to 5.5 -40 to +85 Up to 4.2 0 to 32 Unit V ºC V mA Typical application circuit with external components are shown on page 1. ELECTRICAL OPERATING CHARACTERISTICS VIN = 3.6V, EN = High, ambient temperature of 25ºC (over recommended operating conditions unless specified otherwise) Symbol Parameter IQ Quiescent Current IQSHDN ILED ILED-ACC ILED-DEV Shutdown Current LED Current Range with 6 LEDs LED Current Accuracy LED Channel Matching ROUT Output Resistance (open loop) FOSC ISC_MAX IIN_MAX Charge Pump Frequency Output short circuit Current Limit Input Current Limit EN Pin - Input Leakage - Logic High Level - Logic Low Level Thermal Shutdown Thermal Hysteresis IEN VHI VLO TSD THYS VUVLO Conditions 1x mode, all LEDs Off 1x mode, all LEDs On 1.5x mode, all LEDs Off VEN = 0V Typ 0.5 2.2 3.5 0 0 1mA ≤ ILED ≤ 31mA (ILED - ILEDAVG) / ILEDAVG ±3 ±3 1x mode, IOUT = 120mA 1.5x mode, IOUT = 120mA 0.5 2.8 0.8 VOUT < 0.5V 1x mode, VOUT > 1V 1 60 300 2 Max 1 32 Unit mA mA mA µA mA % % Ω Ω 1.3 MHz mA mA 1 165 20 µA V V ºC ºC 2 V -1 1.3 Undervoltage lock out (UVLO) threshold Doc. No. 5014 Rev. A Min 0.4 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 A.C. CHARACTERISTICS For 3V ≤ VIN ≤ 5.5V, over full ambient temperature range -40 to +125°C (over recommended operating conditions unless specified otherwise). Symbol fSCL tAA tBUF tHD:STA tLOW tHIGH tSU:STA tHD:DAT tSU:DAT tR tF tSU:STO tDH Parameter Clock Frequency SCL Low to SDA Data Out and ACK Out Bus Free Time Before a New Transmission Can Start Start Condition Hold Time Clock Low Period Clock High Period Start Condition Setup Time (For a Repeated Condition) Data In Hold Time Data In Setup Time SDA and SCL Rise Time SDA and SCL Fall Time Stop Condition Setup Time Data Out Hold Time Min Typ Max 400 0.9 1.2 0.6 1.2 0.6 0.6 0 100 0.3 300 0.6 50 Unit kHz µs µs µs µs µs µs ns ns µs ns µs ns Figure 1. I2C Bus Timing Characteristics © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 3 Doc. No. 5014 Rev. A CAT3626 TYPICAL CHARACTERISTICS VIN = 3.6V, IOUT = 90mA (6 LEDs at 15mA), EN = VIN, CIN = C1 = C2 = COUT = 1µF, TAMB = 25ºC, unless otherwise specified. Efficiency vs. Total LED Current (6 LEDs) Efficiency vs. Input Voltage (6 LEDs) 100 1x Mode 100 15mA per LED EFFICIENCY [%] EFFICIENCY [%] 80 70 60 1.5x Mode 50 80 70 60 40 0 4.2 4.0 3.8 3.6 3.4 3.2 3.0 INPUT VOLTAGE [V] Quiescent Current vs. Input Voltage (1x Mode) 0.8 0.6 0.4 6 LEDs OFF 0.2 0 3.0 0.4 0.2 6 LEDs OFF 0.0 QUIESCENT CURRENT [mA]. 3 2 6 LEDs OFF 0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 0 40 80 TEMPERATURE [°C] 120 Quiescent Current vs. Temperature (1.5x Mode) 4 Doc. No. 5014 Rev. A 0.6 -40 5 3.0 0.8 3.2 3.4 3.6 3.8 4.0 4.2 INPUT VOLTAGE [V] Quiescent Current vs. Input Voltage (1.5x Mode) 1 50 100 150 200 TOTAL LED CURRENT [mA] Quiescent Current vs. Temperature (1x Mode) QUIESCENT CURRENT [mA]. QUIESCENT CURRENT [mA] VIN = 3.2V (1.5x mode) 50 20mA per LED 40 QUIESCENT CURRENT [mA]. VIN = 4V (1x mode) 90 90 4.2 5 4 3 2 1 6 LEDs OFF 0 -40 4 0 40 80 TEMPERATURE [°C] 120 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 TYPICAL CHARACTERISTICS VIN = 3.6V, IOUT = 90mA (6 LEDs at 15mA), EN = VIN, CIN = C1 = C2 = COUT = 1µF, TAMB = 25ºC, unless otherwise specified. 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 LED Current Change vs. Temperature 1x Mode 1.5x Mode 3.0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 4.2 -40 CLOCK FREQUENCY [MHz] . 1.3 1.2 1.1 1.0 0.9 0.8 0.7 3.0 3.2 3.4 3.6 3.8 INPUT VOLTAGE [V] 4.0 80 1.3 1.2 1.1 1.0 0.9 0.8 0.7 -40 Output Resistance vs. Input Voltage (1x Mode) 0 40 80 TEMPERATURE [°C] 120 Output Resistance vs. Input Voltage(1.5x Mode) 1.0 4.0 OUTPUT RESISTANCE [Ω] . OUTPUT RESISTANCE [Ω] . -20 0 20 40 60 TEMPERATURE [°C] Oscillator Frequency vs. Temperature Oscillator Frequency vs. Input Voltage FREQUENCY [MHz] . 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 LED CURRENT CHANGE [%] LED CURRENT CHANGE [%] LED Current Change vs. Input Voltage 0.8 0.6 0.4 0.2 0.0 3.0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 4.2 3.5 3.0 2.5 2.0 1.5 1.0 3.0 5 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 4.2 Doc. No. 5014 Rev. A CAT3626 TYPICAL CHARACTERISTICS VIN = 3.6V, IOUT = 90mA (6 LEDs at 15mA), EN = VIN, CIN = C1 = C2 = COUT = 1µF, TAMB = 25ºC, unless otherwise specified. Power Up with 6 LEDs at 15mA (1x Mode) Power Up with 6 LEDs at 15mA (1.5x Mode) Enable Power Down (1x Mode) Enable Power Down (1.5x Mode) Switching Waveforms in 1.5x Mode Operating Waveforms in 1x Mode Doc. No. 5014 Rev. A 6 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 TYPICAL CHARACTERISTICS VIN = 3.6V, IOUT = 90mA (6 LEDs at 15mA), EN = VIN, CIN = C1 = C2 = COUT = 1µF, TAMB = 25ºC, unless otherwise specified. Line Transient Response in 1x mode Foldback Current Limit OUTPUT VOLTAGE [V] 4.0 3.5 3.0 2.5 1x Mode 2.0 1.5 1.0 0.5 0.0 0 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 7 100 200 300 OUTPUT CURRENT [mA] 400 Doc. No. 5014 Rev. A CAT3626 PIN DESCRIPTIONS Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Name LEDA1 SDA SCL EN VOUT VIN C1C1+ C2C2+ GND LEDC2 LEDC1 LEDB2 LEDB1 LEDA2 TAB Function Cathode terminal of LED A1 I2C Serial data input/output I2C Serial clock input Enable input Charge pump output connected to the LED anodes Supply voltage Bucket capacitor 1 terminal Bucket capacitor 1 terminal Bucket capacitor 2 terminal Bucket capacitor 2 terminal Ground reference Cathode terminal of LED C2 Cathode terminal of LED C1 Cathode terminal of LED B2 Cathode terminal of LED B1 Cathode terminal of LED A2 Connect to Ground on PCB PIN FUNCTION VIN is the supply pin for the charge pump. A small 1µF ceramic bypass capacitor is required between the VIN pin and ground near the device. The operating input voltage range is from 2.2V to 5.5V. Whenever the input supply falls below the undervoltage threshold (2V), all LEDs channels will be automatically disabled. 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 1µF ceramic bucket capacitor C1. EN is the enable logic input for the driver. Guaranteed levels of logic high and logic low are set at 1.3V and 0.4V respectively. When EN is initially taken high, the device becomes enabled and all LED currents remain at 0mA. To place the device into zero current shutdown mode, the EN pin must be held low. C2+, C2- are connected to each side of the 1µF ceramic bucket capacitor C2. LEDxx provide the internally regulated current to the six LED cathodes. These pins enter a high-impedance zero-current state whenever the device is placed in shutdown mode. In applications using less than six LEDs, the unused channels should be disabled through the RegEn register. SDA is the I2C serial data line. This is a bidirectional line allowing data to be written into and read from the four registers in the driver. Registers RegA/B/C set the LED current in each pair of channels, while RegEn sets the On/Off state independently of each channel. 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. SCL is the I2C serial clock input. VOUT is the charge pump output that is connected to the LED anodes. A small 1µF ceramic bypass capacitor is required between the VOUT pin and ground near the device. Doc. No. 5014 Rev. A 8 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 BLOCK DIAGRAM Figure 2. CAT3626 Functional Block Diagram BASIC OPERATION LED CURRENT SETTING At power-up, the CAT3626 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 LEDs currents the device remains in 1x operating mode. The LED current setting is programmed via the I2C serial interface and is stored in four 8-bit registers RegA, RegB, RegC and RegEn as follows: If the input voltage is insufficient or falls to a level where the regulated currents cannot be maintained, the device automatically switches (after a fixed time of 400µs) into 1.5x mode. RegA stores the LED current for group A (LEDA1 and LEDA2 channels), RegB stores the LED current for group B (LEDB1 and LEDB2 channels), In 1.5x mode, the output is approximately equal to 1.5 times the input supply voltage (less any internal voltage losses). RegC stores the LED current for group C (LEDC1 and LEDC2 channels), RegEn selects the on/off state of each of the 6 LED channels. At each write access to RegEn, the driver automatically reconfigures to the mode (1x or 1.5x) that provides the highest efficiency. The above sequence is repeated each and every time the chip is either powered-up or taken out of shutdown (via EN pin), or the RegEn register is accessed by write cycle. © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 9 Doc. No. 5014 Rev. A CAT3626 Table 1. Register address and data configuration Register name Register Address RegA RegB RegC 0 1 2 RegEn Bit 7 X X X 3 Bit 6 X X X X Bit pattern Bit 4 Bit 3 Bit 5 Bit 2 Bit 1 Bit 0 See Table 2 for values X LEDC2 LEDC1 LEDB2 LEDB1 LEDA2 LEDA1 On = 1 Off = 0 On = 1 Off = 0 On = 1 Off = 0 On = 1 Off = 0 On = 1 Off = 0 On = 1 Off = 0 Notes: X = not used 1 = logic high 0 = logic low The table 2 lists the various LED currents with the associated RegA, RegB, and RegC register values Table 2. LED Current Selection and Register Value LED current (mA) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 D7 D6 D5 D4 D3 D2 D1 D0 Dec X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 LED current (mA) 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 30.5 31.0 31.5 32.0 D7 D6 D5 D4 D3 D2 D1 D0 Dec X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Notes: X = not used Doc. No. 5014 Rev. A 10 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 I2C INTERFACE The LED driver is interfaced through a 2-wire serial I2C-bus in order to control the state and the current in each of the six LED channels. The SDA and SCL lines comply with the I2C electrical specification and should be terminated with pull-up resistors. When the bus is not used, both lines are high. The device supports the maximum bus speed of 400 kbit/s. The serial bit sequence is shown below for read and write operations into the registers. Read and write Read operation: S instructions are initiated by the master controller/CPU and acknowledged by the slave LED driver. The I2C address of the driver is internally fixed to the binary value 1100110. The protocol requires that the start bit and the device address are both repeated. For further details on the I2C protocol, please refer to the I2C-Bus Specification, document number 9398 393 40011, from Philips Semiconductors. Slave address W A Register address A W A Register address A S Slave address R A Data A* P Write operation: S Slave address Data A P S: Start condition R, W: Read bit (1), Write bit (0) A: Acknowledge sent by the slave LED driver (SDA high) A*: Not Acknowledge sent by the master microcontroller (SDA low) P: Stop condition Slave address: Device address 7 bits (MSB first, slave address is 1100110). Register address: Device register address 8 bits Data: Data to read or write 8 bits Write Instruction Sequence © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 11 Doc. No. 5014 Rev. A CAT3626 Write Instruction Example setting 20mA current in LEDB1 and LEDB2 I2C Bus Protocol TYPICAL APPLICATION The CAT3626 is ideal for driving RGB (red green blue) LEDs with common anode configuration. The individual LED currents associated with the red, green and blue LEDs are programmable independently through the I2C interface, allowing to generate an accurate color mixing. Dimming while maintaining the same color can be done by reprogramming the RegEn register on and off with the appropriate duty cycle (PWM mode). RGB LED Doc. No. 5014 Rev. A 12 © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice CAT3626 PACKAGE DRAWING AND DIMENSIONS Thin QFN 16-Lead 4mm x 4m © 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice 13 Doc. No. 5014 Rev. A REVISION HISTORY Date 03/20/2006 Rev. A Reason Initial Issue Copyrights, Trademarks and Patents Trademarks and registered trademarks of Catalyst Semiconductor include each of the following: DPP ™ AE2 ™ Catalyst Semiconductor has been issued U.S. and foreign patents and has patent applications pending that protect its products. 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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 1250 Borregas Avenue Sunnyvale, CA 94089 Phone: 408.542.1000 Fax: 408.542.1200 www.catsemi.com Document No: 5014 Revision: A Issue date: 03/20/2006