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From your note, I understand I have to place a 1meg ohm resistor in series with the three units which are in parallel. That high of a resistance will not let the 1000ma pass will it? Going across a straight 12v, a 1meg resistor will only allow 12micro amps. Maybe I misunderstood the note. Can you clarify?
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From: onhelp@onsemi.com
To: dsdrewyor@comcast.net
Sent: Monday, February 2, 2015 6:14:26 PM
Subject: Ask An Expert Notification
Your question:
I have an LED that has a Fv of 3.3v and up to 1000ma drive requirement. My drive source is a PWM signal at 12vdc up to the 1000ma max. What can I use to limit the drive voltage to the LED while still getting the current I need? I have used dropping resistors in the past, but these would be very large resistors. Thanks Dave
has been answered:
You can use our NSI50350AS LED Driver, Constant Current Regulator, 350 mA, 50 V and connect three of them parallel with 1 m Ohm resistor in series.
This configuration will limit your LED current to 1 Amp.
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Kind regards, ON Semiconductor
Hello,
Series resistor value should read 1 milliohm not Mega ohm. Let me know if you have any other questions.
Answered by: ON Semiconductor
2015-02-16 10:03:38.18