Dec18,2006 RevB

SP6687 Evaluation Board Manual

© 2006 Sipex Corporation

Page 2 of 4

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

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

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

Control Inputs

Output Status

CTRL2

CTRL1

CTRL0

LED4

LED3

LED2

LED1

0

0

0

OFF

OFF

OFF

ON

0

0

1

OFF

OFF

ON

OFF

0

1

0

OFF

ON

OFF

OFF

0

1

1

ON

OFF

OFF

OFF

1

0

0

OFF

OFF

ON

ON

1

0

1

OFF

ON

ON

ON

1

1

0

ON

ON

ON

ON

1

1

1

OFF

OFF

OFF

OFF