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SP6687
TM
Evaluation Board Manual
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High Efficiency > 90% Support up to 4 white LEDs Soft Start Function Short Circuit Protection Three Charge Pump Modes: X1, X1.5, X2 1MHz Fixed Frequency Oscillator
DESCRIPTION AND BOARD SCHEMATIC The SP6687 Evaluation Board is designed to help the user evaluate the performance of the SP6687 for use as a 4 LED Driver with matched currents. The evaluation board is a completely assembled and tested surface mount board which provides easy probe access points to all SP6687 inputs and outputs so that the user can quickly connect and measure electrical characteristics and waveforms. The Evaluation Board schematic diagram is shown at Figure 1.
Figure 1. SP6687 Evaluation board Schematic Diagram
Dec18,2006 RevB
SP6687 Evaluation Board Manual Page 1 of 4
(c) 2006 Sipex Corporation
The SP6687 is a high efficiency charge pump white LED driver. It provides 4 channels of low drop-out voltage current source to regulate the current for 4 white LEDs. For high efficiency, the SP6687 implements a 3 mode charge pump: x1, x1.5, and x2. An external resistor R5 is used to set the current of the white LEDs. SP6687 has an input current regulation to reduce the input ripple. Users can control white LED on/off via three programming bits: CTRL0, CTRL1 and CTRL2. When an external PWM signal is connected to the control pin, the brightness of white LEDs is adjusted by the duty cycle. Each channel can support up to 30mA of current. A current limiting circuit is also included in the SP6687 for short circuit protection. Whenever the output sources a dangerously high current, the current limiting circuit takes over the output regulation circuit and reduces the output current to an acceptable level. This device is available in a 4mm x 4mm, 16 pin QFN package. Capacitor C1 is a decoupling capacitor. Resistors R1 - R4 are used to pull down inputs if they are left floating. Capacitors C2 - C4 are used by the charge pump. USING THE EVALUATION BOARD 1) Powering Up the SP6687 Circuit The SP6687 Evaluation Board can be powered from a 4.5V power supply or from 3 alkaline cells. Connect 4.5V source pin with short lead directly to the "Vin" and -4.5V /GND pin to the "GND" posts. 2) Selecting the Bias Resistor LED current can be adjusted up to 30mA per string with an external resistor R5. The R5 value may be determined as ILED = 440x (Voltage at ISET /R5), where ILED is required LED current, and Voltage at ISET = 1.1V. R5 = 32 k is installed. 3) Selecting the number of illuminated LEDs The number of illuminated LEDs can be selected using CTRL0 - CTRL2 programming bits (see Table 1). Table 1. Programming Table
CTRL2 0 0 0 0 1 1 1 1 Control Inputs CTRL1 0 0 1 1 0 0 1 1 CTRL0 0 1 0 1 0 1 0 1 LED4 OFF OFF OFF ON OFF OFF ON OFF Output Status LED3 LED2 OFF OFF OFF ON ON OFF OFF OFF OFF ON ON ON ON ON OFF OFF LED1 ON OFF OFF OFF ON ON ON OFF
Dec18,2006 RevB
SP6687 Evaluation Board Manual Page 2 of 4
(c) 2006 Sipex Corporation
20 Voltage, V, Current x 10mA 18 16 14 12 10 8 6 4 2 0 2 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage, V Iin x 10mA (rising) Vout, V (falling) Vout, V (rising) Iin x 10mA (falling)
Graph 1. Input Current and Vout Voltage vs. rising and falling Input Voltage at R5 = 20 k (4 LEDs are on)
EVALUATION BOARD LAYOUT
Figure 2. SP6687 Evaluation Board Layout top side
Dec18,2006 RevB
SP6687 Evaluation Board Manual Page 3 of 4
(c) 2006 Sipex Corporation
Table2. SP6687EB List of Materials
Reference C1 - C4 D1 - D4 P1 - P9 R1 - R4 R5 S1 - S4 U1 Quantity 4 4 9 4 1 4 1 Value 1uF Description 06033D105KAT2 AVX SML-LX2832UWC-TR Vishay 1001-0-15-01-30-02-04-0 Mill-Max CRCW0603105J100RT6 Vishay CRCW0603243J100RT6 Vishay Header 4030-22-10-2031 Molex SP6687 Sipex
1M 24k
ORDERING INFORMATION Model Temperature Range Package Type
SP6687EB .................................................. -40 to +85 ......................................... SP6687 Evaluation Board C C SP6687ER-L/TR .......................................... -40 to +85 .............................Lead Free 16 Pin 4mmx4mm QFN C C /TR = Tape and Reel Pack quantity is 2,500 for QFN.
For further assistance: Email: WWW Support page: Live Technical Chat: Sipex Application Notes: Sipexsupport@sipex.com http://www.sipex.com/content.aspx?p=support http://www.geolink-group.com/sipex/ http://www.sipex.com/applicationNotes.aspx
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Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA95035 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.
Dec18,2006 RevB
SP6687 Evaluation Board Manual Page 4 of 4
(c) 2006 Sipex Corporation

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