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Topic: [SOLVED] TLC 5940 Max current sink. (Read 616 times) previous topic - next topic

AJB2K3

Mar 30, 2013, 09:58 am Last Edit: Mar 30, 2013, 12:49 pm by AJB2K3 Reason: 1
Apologies in advance but I'm scratching my head over the data sheet.

I am planning on running this on a 3.6V circuit and my prototype scrolls through 15 20mA led's.
Will this chip be able to handle running 4 led's on each pin? (80mA?) while (on rare occasion) fade all 60?

Sorry but i'm having (whats know in the UK) a blond moment here.
Sorry for the noobish post but my knowledge is 10 years out of date!

Coding Badly


Forward voltage of the LEDs?

Voltage of the LED power supply?  3.6V?

AJB2K3



Forward voltage of the LEDs?

Voltage of the LED power supply?  3.6V?


Well my led's are 20mA each 3.2-3.V @ 20mA total per pin load = 80mA!
Sorry for the noobish post but my knowledge is 10 years out of date!

fungus


I am planning on running this on a 3.6V circuit and my prototype scrolls through 15 20mA led's.
Will this chip be able to handle running 4 led's on each pin? (80mA?) while (on rare occasion) fade all 60?


The datasheet says:

60 mA (VCC < 3.6 V)
120 mA (VCC > 3.6 V

It doesn't say what happens when VCC=3.6V but 80mA is right in the middle...

You're planning on having the chip dissipate about 0.5V per channel (3.6 minus 3.1). 0.5V*80mA*16 channels=640mW. That's well within the limits for power dissipation.

You should be fine.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

AJB2K3



I am planning on running this on a 3.6V circuit and my prototype scrolls through 15 20mA led's.
Will this chip be able to handle running 4 led's on each pin? (80mA?) while (on rare occasion) fade all 60?


The datasheet says:

60 mA (VCC < 3.6 V)
120 mA (VCC > 3.6 V

It doesn't say what happens when VCC=3.6V but 80mA is right in the middle...

You're planning on having the chip dissipate about 0.5V per channel (3.6 minus 3.1). 0.5V*80mA*16 channels=640mW. That's well within the limits for power dissipation.

You should be fine.


Thanks fungus
Sorry for the noobish post but my knowledge is 10 years out of date!

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