Dec 7-06

SP7618 Evaluation Board Manual

© 2006 Sipex Corporation

Page 2 of 6

The SP7618 Evaluation Board is designed to help the user evaluate the performance of the SP7618 for use as a

single photo flash Luxeon LED Driver. The evaluation board is a completely assembled and tested surface mount

board which provides easy probe access points to all SP7618 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.

The SP7618 is a linear low side constant current driver designed to drive high power LEDs from an input voltage

rail. The driver acts as a high current source ensuring constant LED current for a range of input voltage. The

SP7618 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 adjusted up to 1033mA with an external clock applied to the CTRL pin. The built-in thermal

protection automatically stops LED current to prevent overheating. A timeout function serves as a fail safe, shutting

down the output for currents greater than 266mA after 4 seconds of continuous operation if the enable input is not

cycled. The part can be shutdown by using the EN pin or holding the CTRL pin low for more than 100µS.

The evaluation board contains SP7618 driver (U2) with one Luxeon Flash LED as a load (D1) and pulse generator.

The pulse generator (U1, U4, and U5) is used to provide a pulse sequence to the driver’s CTRL and EN pins to set

LED current and turn the driver on/off. The number of pulses that determines LED current may be set by 5-bit dip-

switch (U3) using binary code. The number of pulses depend on switch position is shown on Table 1.

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USING THE EVALUATION BOARD

1) Selecting the LED current

LED current can be adjusted up to 1033mA with a series of pulses applied to the CTRL pin. Each pulse increases

the output current in steps of 33.33mA. The maximum number of the pulses is 31. The 32

are ignored. The number of pulses depends on the switch position as shown on Table 1, which is on the next page.