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I have a LED backlight driver, which has input pin assignment as:

Pin Function

1,2 12V Input

3 Brightness control PWM : 100Hz~20KHz DC : 0.5V~2.5V

4,6 GND

5 ON/OFF Control 5V ON , 0V OFF

Why do pin 1 and 2 both require 12V input, what is the utility of that? Can somebody give insights on why didn't they use just one pin and give input internally using the same pin?

Link to the datasheet.

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1 Answer 1

up vote 7 down vote accepted

IC manufacturers use more than one pin on a device if the device is a high current device.

As a LED driver, it's likely a high-current device and thus needs more than 1 pin to share the current load through the device.

EDIT: After seeing the spreadsheet , it seems this particular device is not really very high power after all, at only 800mA total, so one further possibility is that the designers wanted to use the extra connections to power and ground to help dissipate heat from the chip to the PCB though the power leads.

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Thanks. That makes sense. But i have one power supply that gives one 12V output and i am giving the pins power using the same pin. On their part How is it different than taking power from just one pin and diving it into two different PCB traces ? –  rajat Feb 21 '14 at 12:58
The difference is the power entering the chip through two pins, vs your example where the power still enters the chip on one pin but uses two traces on the PCB. Think of where the current divides... –  Brian Onn Feb 21 '14 at 13:30
What you say abiut sharing current is true in cases like the cpu power in a pc where up to 8 separate wires are used but in this case the spreadsheet says Drives 4 channels of LEDs at Up to 200mA so up to 800mA total is hardly a high-current device and doesn't justify the use of two pins. –  alexan_e Feb 21 '14 at 13:37
yes I just saw the spreadsheet too, it's only 800mA total, which is not a very high current. One other possibility could be that the designers wanted to use the lead frame to dissipate heat better to the PCB traces. –  Brian Onn Feb 21 '14 at 13:41
@BrianOnn: It may be worth noting that lead frames where two pins are permanently connected may have both pins be a continuous piece of metal over much of the distance from the die to the board. This may make more metal available to carry heat than would have been possible using separate pins. –  supercat Feb 21 '14 at 21:08

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