SP7615 datasheet(4/10 Pages) SIPEX

4 / 10 page

Date: 08/31/05

SP7615 Four Channel Constant Current LED Driver

THEORY OF OPERATION

VCC

GND

LED

SP7615

GND

LED1

VCC

ISET

LED2

LED3

LED4

The R

SET value may be determined as RSET =

1.26 * 1000/I

OUT, kΩ where 1.26 is a typical

SET pin voltage, 1000 is a typical current

multiplication ratio, and I

OUT is a required

LED current in mA.

The voltage applied to the cathode of each

LED determines the overall efficiency of the

SP7615 circuit. The SP7615 is designed to

be able to sink 125mA at each of its four

outputs; LED1 - 4. The SP7615 is also

designed to be able to handle up to 16V on

these pins. This voltage handling capability

assumes the total power can be dissipated

by the SP7615. The power dissipation inside

the SP7615 will de directly related to the

voltage and current applied to these pins.

For example, the typical operating cathode

voltage is 500mV. At maximum current the

VCC

GND

SP7615

GND

LED1

VCC

ISET

LED2

LED3

LED4

SP7615

GND

LED1

VCC

ISET

LED2

LED3

LED4

power dissipated by one LED driver output

is 125mA * 500mV = 62.5mW. The following

charts show the power dissipation of the

SP7615 under various conditions. The

power dissipation should be kept below

1.3W for safe operation and long term

reliability at room temperature and derates

to 530mW at 85ºC. While the above

operating conditions are recommended, the

part cannot be damaged due to internal

temperature control as described above in

the thermal shutdown section.

CATHODE VOLTAGE, SUPPLY VOLTAGE

AND POWER DISSIPATION

SP7615 Datasheet(PDF) 4 Page - Sipex Corporation

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