Solved by
SP6687
TM
Evaluation Board Manual
•
•
•
•
•
•
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
© 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
I
LED
= 440x (Voltage at I
SET
/R5), where I
LED
is required LED current, and Voltage at I
SET
=
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
© 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
© 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
Solved by
TM
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
© 2006 Sipex Corporation
京公网安备 11010802033920号
EEWORLD
