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Solved by
SP7619/19A
TM
Constant Current LED Driver
FEATURES Very low dropout voltage (60mV@200mA) Accurate current regulation down to dropout voltage No external components Selectable output current levels: 200mA & 500mA (700mA for SP769A) Power-saving shutdown mode of A Fast turn-on (<50s) Timeout function to protect the LED Thermal Shutdown protection RoHS compliant, Lead Free packaging: Space saving 2mmx3mm 8pin DFN
LED LED VCC EN
1 2 3 4
SP7619
8 Pin DFN
8 GNDP 7 GNDP 6 GND 5 CTRL

APPLICATIONS Next Generation Mobile Phones PDA, DSC, MP3 Players Handheld Computers LCD Display Modules
GENERAL DESCRIPTION The SP769 is a linear low-side, constant-current driver designed to drive high power LEDs from an input voltage rail. The driver acts as a current source, ensuring constant LED current across a range of input voltages. The SP769 allows implementing the lowest cost LED driver for a variety of applications. Internal circuitry maintains the preset constant current output for a wide voltage range at the LED input. The LED current can be set at 200mA at torch mode or 500mA (700mA SP7619A) at flash mode by selecting CTRL pin low/high respectively. Dimming or shutdown can be done by feeding a PWM signal to the EN pin. Fast EN turn-on/off time allows for very fast dimming frequencies, completely eliminating flicker. The built-in thermal protection automatically stops LED current to prevent overheating. A timeout function serves as a fail safe, shutting down the output at 500mA (700mA) current after 4 seconds of continuous operation if the enable input is not cycled. The Enable pin should be cycled HIGH/LOW/HIGH to restart the driver. TYPICAL APPLICATION CIRCUIT
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Constant Current LED Driver
(c) 2007 Sipex Corporation
Supply Voltage (Vcc) ..............................6.0V Input Voltage at any input .....-0.6V to Vcc +0.5V 8-pin DFN Package thermal resistance 59C/W Junction Temperature ............. -40C to +70C* Storage Temperature ..............-65C to +50C Soldering Temperature .....................+240C**
*) Internally limited **) Duration 0s maximum
ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. ELECTRICAL CHARACTERISTICS
CONDITIONS EN = GND, CTRL = DC EN = Vcc, CTRL = Vcc CTRL pin LOW SP769 CTRL pin HIGH SP769A CTRL pin HIGH 3.0 < Vcc < 5.5V,Vled =V .0 < Vled < 2.5V, Vcc = 5.5V Iled = 200 mA Iled = 500mA for SP769@25C Iled =700 mA for SP769A@25C Iled =200 mA for both SP769 & SP769A @25C Iled = 200mA
Ambient temperature Ta = 25C, 3.0V < Vcc < 5.5V, .0V < Vled < 3.0V. Bold denotes specifications which apply over the full operating temperature range, -40C to +85C.
PARAMETER Vcc Voltage Operating Range Shutdown Mode Supply Current After Time Duration 2 LED Output Current LED Current Line Regulation 3 LED Current Load Regulation 4 LED Current Thermal Regulation
MIN 2.5
TYP
MAX 5.5
UNITS V A
350 80 450 630 200 500 700 0. .5 0.0 75
420 220 550 770 0.5 6
mA %/V % %/C
60 85 40 C 50 50 30 C s s s s V mV
VLED Dropout Voltage 5
90 60
Thermal Shutdown Die Temperature Thermal Shutdown Hysteresis Setup Time 6 Wake-up Time from Shutdown Turn-off Time into Shutdown Time Duration before Sleep Mode LOW EN and CTRL pin Logic Voltage HIGH
Notes: . 2. 3. 4. 5. 6. 7.
60 25
2 1.4
4
7 0.4 Vcc7
EN = LOW to HIGH, CTRL = DC EN = HIGH to LOW, CTRL = DC Iled = 500/700 mA, EN = HIGH, CTRL = HIGH Driver in Shutdown Mode 2.5V Vcc 5.5V
Vcc must be always higher than LED pin voltage (Vled) After 4s at 500 (700) mA current Iled variations per volt Vcc change Iled variations at Vled change from to 2.5V 5% change of Iled compared with Iled value at Vled = V Iled settles 50s later after CTRL from LOW to HIGH or from HIGH to LOW Logic HIGH level should never exceed Vcc voltage
Constant Current LED Driver (c) 2007 Sipex Corporation
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PIN ASSIGNMENTS
Pin # -2 3 4 5 6 7-8 Pin Name LED Vcc EN CTRL GND GNDP Pin Function LED Current Sink. Connect LED cathode to this pin. Voltage at this pin should be above 00 mV to maintain regulation. Power Supply Input. Place F decoupling capacitor next to this pin Enable/Shutdown pin used to enable/disable driver and reset time count Logic High - enable, Logic Low - disable/reset.
This pin is used to switch Iled current between two internally preset levels for Flash or Torch mode. CTRL = LOW selects Torch mode (200mA), CTRL = HIGH selects Flash mode 500 (700)mA.
Ground pin for control and bias blocks. Ground pin. LED current flows through this pin to ground.
BLOCK DIAGRAM
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Constant Current LED Driver
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APPLICATION INFORMATION
24 22 20
3 2
Error, %
Iled, mA
208 206 204 202 200 98 0 00 200 300 Vled, mV 25C 85C 400 500 600
0 - -2 -3 -4 -5 Vled, V 200mA 700mA 0 0.5 .5 2 2.5 3 3.5
SP769 Load regulation at 200mA Iled current
SP769A Load Regulation at 25C
550 500 450
Iled, mA
400 350 300 250 200 0 00 200 Vled, mV 25C 85C 300 400 500
SP769 Load regulation at 500mA Iled current
SP769 PWM modulation (Channel - PWM signal 1kHz, 20% Duty cycle, 2V/div, Channel 3 -Iled current - 1mV is equal 10mA current)
0.3 0.2 0.
Error, %
0 -0. -0.2 -0.3 -0.4 Vcc, V 200mA 700mA 2.5 3 3.5 4 4.5 5 5.5 6
SP769A Line Regulation at 25C
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THEORY OF OPERATION Introduction The SP769 is a linear low-side constant -current driver designed to drive high power LEDs from an input voltage rail. The design consists of a regulator reference voltage source, voltage-to-current converter, thermal shutdown, timeout shutdown, and output driver. The precision reference voltage ensures good performance over voltage and temperature. The built-in thermal protection automatically stops LED current to prevent overheating. A timeout function serves as a failsafe, shutting down the output at Flash Mode after 4 seconds of continuous operation if the enable input is not cycled. Current Setting The LED output current is defined by internal circuitry. The input to this circuitry is the CTRL pin. LOW logic level determines Torch Mode while HIGH logic level determines Flash Mode with appropriate output currents. The ENABLE pin and CTRL pin logic HIGH level may be applied with Vcc voltage. At Flash Mode the maximum Time Duration is 4s. After that, the device is automatically sent into Sleep Mode. This function is intended to protect the LED if, for example, the device was left on in a high current condition for a long period of time. To return the device to the Flash Mode use Shutdown (EN = HIGH to LOW/LOW to HIGH). Switching the CTRL pin LOW during Sleep Mode sets the device into Torch Mode. The LED output current will reach its final value 50s after the CTRL pin transition from LOW to HIGH or from HIGH to LOW. Output Driver The SP769 features a low-side regulated output current driver. A large MOSFET device is connected between the LED and GNDP
Feb 9-07 Rev E
pins. The MOSFET drain is connected to the LED pins and the MOSFET source is connected to the GNDP pins. There are two pins on each terminal of the MOSFET in order to minimize power dissipation inside the package. Even though there are two LED and GNDP pins, there is actually only one output intended to drive one LED. The light emitting diode connects from VCC to LED pins. The Iled current regulation is guaranteed at dropout at the LED pins to be less than 00mV. The regulation attempts to maintain the output current to within five percent of nominal even if the voltage between the LED and GNDP pins varies over a wide range. The nominal output is guaranteed within 10% of the defined current. Thermal Protection The SP769 has built-in thermal protection. An internal p-n junction is compared to the internal temperature-compensated reference. When the p-n junction reaches a temperature specific voltage it trips a comparator which shuts down the driver stage of the part, placing the device into sleep mode while current setting circuitry remains active. The shutdown temperature is defined to be 60C typical. The comparator circuit has built-in hysteresis corresponding to 25C. The output stage will resume operation and start sinking the current that was defined prior to shutdown when the internal temperature drops by 25C. If the part remains in a high ambient temperature environment or if a high power dissipation condition exists, the output stage will cycle on and off to maintain a preset internal junction temperature to avoid catastrophic damage. In that case, the LED will appear to be blinking. Lower the LED voltage to avoid excess power dissipation in the IC.
(c) 2007 Sipex Corporation
Constant Current LED Driver
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APPLICATION INFORMATION Shutdown The SP769 has a low current shutdown function. In shutdown mode the part draws less than A current maximum. The part can be placed into shutdown using the EN pin. ENABLE and CTRL pins cannot be tri-stated or left floating. There are no predefined internal states, so leaving these pins open will cause the part to operate incorrectly. Timeout A Time Duration Before Shutdown feature acts as a failsafe to protect the LED from long ON times. The nominal timeout is defined as 4 seconds at 500 (700)mA output current. Power-on-Reset This function is used to set Time Duration counters into their initial state after power up. No signal applied to the CTRL pin can be accepted during this time, even if the input voltage is applied simultaneously to the Vcc and ENABLE pins.
BOARD LAYOUT AND GROUNDING
To obtain the best performance from the SP769, a printed circuit board with ground plane is required. High quality, low series resistance ceramic F bypass capacitors should be used at the Vcc pin (pin 3). These capacitors must be located as close to the pins 3 - 6 as possible. The traces connecting the pins and the bypassing capacitor must be kept short and should be made as wide as possible. Pins - 2 are connected together internally but we recommend connecting the LED cathode
to both pins to avoid additional power losses at high current. Pins 6, 7 and 8 should be connected to the ground plane. Board layout should prevent high LED ground current from flowing through signal ground connected to pin 6. This pin is a separate ground for the reference and logic sections of the SP769. The quiescent current for the part flows into the VCC pin and out of the GND pin. This current is proportional to the Iled current divided by approximately 500.
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PACKAGE: 8 PIN DFN
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Constant Current LED Driver
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ORDERING INFORMATION
Part Number
Operating Temperature Range
Package Type
SP769ER-L...................... ....................-40 C to +85 C .................. ..............8 Pin DFN (Lead Free, 2mm x 3mm) SP7619ER-L/TR ............... ................... -40 C to +85 C .................. ..............8 Pin DFN (Lead Free, 2mm x 3mm) SP769AER-L .........................................-40 C to +85 C ...................................8 Pin DFN (Lead Free, 2mm x 3mm) SP7619AER-L/TR ...................................-40 C to +85 C .................. ..............8 Pin DFN (Lead Free, 2mm x 3mm) /TR = Tape and Reel Pack quantity is 3,000 for DFN.
Solved by
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600
TM
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. Feb 9-07 Rev E Constant Current LED Driver (c) 2007 Sipex Corporation
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