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(R)
Preliminary
SP7615
Four Channel Constant Current LED Driver
FEATURES Cost Effective LED driver VCC 1 8 LED1 Constant current output ideal for Driving LED strings SP7615 7 LED2 EN 2 Four Channel LED Driver provides matched LED 6 LED3 GND 3 8 Pin DFN current ISET 4 5 LED4 Current adjusted via an external resistor PWM dimming possible Now Available in Lead Free Packaging Small 2mm x 3mm DFN package Outputs can be connected in parallel to APPLICATIONS increase drive Constant current for wide cathode voltage range Next Generation Mobile Phones (1.0V to 16V) PDA, DSC, MP3 Players Highly integrated design, minimal components Handheld Computers LCD Display Modules Thermal shutdown protects the driver Keyboard Backlight LED Displays DESCRIPTION The SP7615 is a linear constant current driver designed to drive multiple LEDs in series from a high input voltage rail. The driver acts as a high current matched, four-channel current source ensuring constant LED current for a range of input voltages. The SP7615 allows implementing the lowest cost LED driver for a variety of applications. Internal circuitry maintains the pre-set constant current output for a wide voltage range at the LED outputs (LED1,2,3,4). LED current can be adjusted up to 125mA per string with an external resistor. The dimming can be achieved by controlling the ISET input or by feeding a PWM signal to the EN pin. Fast EN turn-on and turn-off time allows for very fast PWM dimming frequencies, completely eliminating flicker. The built-in thermal protection automatically adjusts LED current to prevent overheating. TYPICAL APPLICATION SCHEMATIC
VCC EN C1 1n GND
Date: 08/31/05
VCC EN GND SP7615
LED1
(R)
LED2 LED3 LED4
R1
ISET
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
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ABSOLUTE MAXIMUM RATINGS
Vcc, VLED1, VLED2, VLED3, VLED4 Voltage to GND 0.3V to 16V ISET and EN Voltage to GND..................................... 6V These are stress ratings only and functional operation Output Current per LED (IOUT) ............................. 150mA of the device at these ratings or any other above those Power Dissipation per Package indicated in the operation sections of the specifications 8-pin DFN at TA = 85C ......................... 1.1W below is not implied. Exposure to absolute maximum Junction Temperature ..........................................+150C rating conditions for extended periods of time may affect Storage Temperature ........................... -55C to +150C reliability. ESD Level. ....................................................... 2kV HBM
DFN Thermal Resistance......................................59C/W
ELECTRICAL CHARACTERISTICS
4.5V < VCC <16V , VEN = 5V, VLED1 =VLED2 =VLED3 =VLED4 =1.0V, RSET =10k or ISET=126A, -40 < TA < 85C, Unless otherwise noted. Typical numbers are for TA = 25C.
PARAMETER Supply Voltage Quiescent Supply Current Output/I SET Current Multiplication Ratio LED Current (per diode) LED to LED Current Matching LED Current Line Voltage Regulation LED Current Load Voltage Regulation LED Current Thermal Regulation ISET Pin Voltage Thermal Shutdown Threshold Thermal Shutdown Hysteresis Current in OFF Mode Min. ENABLE "ON Voltage" (Note1) Max. ENABLE "OFF Voltage" (Note 2)
MIN. 4.5
TYP. 5 20
MAX. 16 39 1200
UNITS V mA
CONDITIONS
ILED1 = ILED2 = ILED3= ILED4 =126mA
700
1000 126
mA 5 % %/V %/V %/V %/C 1.39 V C C 1 1.6 A V V VEN = ZeroV IOUT change per volt VCC change 0.4V < VLED < 5V, ILED = 25mA 1.0V < VLED < 5V, ILED = 126mA ILED = 126mA ISET = 1A
-5 0.15 2 9 0.1 1.17 1.26 150 20
0.6 4
0.4
Note 1. ENABLE "ON" is VEN for which ILED > 80mA Note 2. ENABLE "OFF" is VEN for which ILED < 1uA@ VLED1 > 1.0V
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
2
BLOCK DIAGRAM
LED1 VCC Thermal Shutdown GND Bias Driver LED3 EN V to I Converter LED4 LED2
Figure 1. SP7615 Block Diagram
ISET
THEORY OF OPERATION
Introduction The SP7615 is a four channel constant current source LED driver with programmable output current level. The design consists of a regulator bandgap, voltage to current converter, and output mirror drivers. The bandgap ensures good performance over voltage and temperature. The four outputs are tightly coupled allowing for excellent channel matching. Thermal Shutdown The SP7615 uses a thermal comparator to monitor the system temperature shutting the device down if the internal temperature reaches 150C. The device will remain off until the internal temperature drops below 130C. Enable The device has an enable function that is designed for TTL level inputs. This input will also track the VCC pin so levels up to VCC are
Date: 08/31/05
acceptable. The enable pin can also be used to control the LED brightness with a pulse width modulated control signal. Duty Cycle or PWM control of the LED current maintains constant LED color while brightness is changing. The SP7615 responds in less than 10s to PWM signals applied to this pin. ISET Pin
The ISET pin is the servo point of an amplifier configured as a voltage to current converter. The voltage at this pin trips servos to the internal bandgap potential. A set resistor can be connected from the ISET pin to ground to generate a reference current for the following current gain stages. A current could alternately be applied to this pin in the form of a current source or current output DAC. This pin can also have a PWM signal applied to control the LED brightness.
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
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THEORY OF OPERATION The RSET value may be determined as RSET = 1.26 * 1000/IOUT, k where 1.26 is a typical ISET pin voltage, 1000 is a typical current multiplication ratio, and IOUT is a required LED current in mA.
D1 LED VCC EN C1 1n GND R1
VCC EN GND ISET SP7615 LED1
(R)
LED2 LED3 LED4
VCC EN C1 1n R1
VCC EN GND ISET SP7615
LED1
(R)
LED2 LED3 LED4
VCC EN GND SP7615
LED1
(R)
LED2 LED3 LED4
GND
R2
ISET
CATHODE VOLTAGE, SUPPLY VOLTAGE AND POWER DISSIPATION The voltage applied to the cathode of each LED determines the overall efficiency of the SP7615 circuit. The SP7615 is designed to be able to sink 125mA at each of its four outputs; LED1 - 4. The SP7615 is also designed to be able to handle up to 16V on these pins. This voltage handling capability assumes the total power can be dissipated by the SP7615. The power dissipation inside the SP7615 will de directly related to the voltage and current applied to these pins. For example, the typical operating cathode voltage is 500mV. At maximum current the power dissipated by one LED driver output is 125mA * 500mV = 62.5mW. The following charts show the power dissipation of the SP7615 under various conditions. The power dissipation should be kept below 1.3W for safe operation and long term reliability at room temperature and derates to 530mW at 85C. While the above operating conditions are recommended, the part cannot be damaged due to internal temperature control as described above in the thermal shutdown section.
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
4
PERFORMANCE GRAPHS
Figure 2 - Four Channel Total Power Dissipation versus Cathode Voltage at VCC = 5V
Figure 3 - Four Channel Total Power Dissipation versus Supply Voltage at Vcathode = 500mW
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
5
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 4 - LED Current versus ISET Current and Cathode Voltage, Vcc=5V, T= 27C
Figure 5 - LED Current versus RSET Value
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
6
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 6 - LED Current versus Temperature with Thermal Shutdown
Figure 7 - ISET Voltage versus Temperature
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
7
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 8 -PWM Signal Applied To The Enable Pin, Amplitude=5V, Duty Cycle=50%
Date: 08/31/05
SP7615 Four Channel Constant Current LED Driver
(c) Copyright 2005 Sipex Corporation
8
PACKAGE: 8 PIN DFN
D D/2
5 6
D2 D2/2
7 8
E/2
E2/2
E
E2
L
4 3 2 1
K e b
INDEX AREA (D/2 x E/2)
Pin1 Designator to be within this INDEX AREA (D/2 x E/2)
TOP VIEW
BOTTOM VIEW
o
A (A3) A1
Seating Plane
SIDE VIEW
2x3 8 Pin DFN SYMBOL
JEDEC MO-229
VARIATION VCED-2 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MIN 0.032 0.000 0.008 0... 0.008 0.059 0.063 0.012 NOM 0.036 0.001 0.008 REF 0.010 0.079 BSC 0.118 BSC 0.020 BSC 0.016 MAX 0.039 0.002 14... 0.012 0.069 0.075 0.020
Dimensions in Millimeters: Controlling Dimension MIN 0.80 0.00 0.20 0... 0.18 1.50 1.60 0.30 NOM 0.90 0.02 0.20 REF 0.25 2.00 BSC 3.00 BSC 0.50 BSC 0.40 MAX 1.00 0.05 14... 0.30 1.75 1.90 0.50
A A1 A3 K b D D2 E E2 e L
SIPEX Pkg Signoff Date/Rev:
Date: 08/31/05
JL Aug18-05 / RevA
(c) Copyright 2005 Sipex Corporation
SP7615 Four Channel Constant Current LED Driver
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ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP7615ER .................................................. -40C to +85C ............................................ 8 Pin DFN (2 x 3mm) SP7615ER/TR ............................................ -40C to +85C ............................................ 8 Pin DFN (2 x 3mm) Available in lead free packaging. To order add "-L" suffix to part number. Example: SP7615ER/TR = standard; SP7615ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 3000 for DFN.
Corporation
ANALOG EXCELLENCE
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver (c) Copyright 2005 Sipex Corporation
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