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Indicator LED connected to DAC

 
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knutolai



Joined: 23 Nov 2016
Posts: 29
Location: Bergen, Norway

PostPosted: Tue Sep 05, 2017 11:31 am    Post subject: Indicator LED connected to DAC Reply with quote

Hey

So I'm writing a program where I use DACR to display a waveshape. Everything is working flawlessly but whenever DACR outputs a value close to 1 or -1 the clip LED lights up. Is this in any way harmful to the chip?

I'm guessing "no", but I always get the vibe that when a clipping indicator for a DSP lights up I'm doing something harmful to the hardware.

-Knut Olai
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frank



Joined: 19 Oct 2005
Posts: 958

PostPosted: Tue Sep 05, 2017 12:00 pm    Post subject: Reply with quote

No, nothing bad is happening to the chip in this case, it is just the clip circuit detecting the large values. If it bothers you just lower the max output to below clipping.
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Frank Thomson
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knutolai



Joined: 23 Nov 2016
Posts: 29
Location: Bergen, Norway

PostPosted: Wed Sep 13, 2017 3:37 am    Post subject: Reply with quote

Thank you Frank! I'm driving the LED directly with the output from DACR:
DACR -> Resistor -> LED -> Ground

I've read elsewhere on the forum of people using a LED driver solution where DACR connects to the gate of a NPN transistor that switches the LED on or off.

Is there any reasons to not driver the LED directly with the DACR output?
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frank



Joined: 19 Oct 2005
Posts: 958

PostPosted: Wed Sep 13, 2017 8:00 am    Post subject: Reply with quote

The DAC outputs are not designed to drive very much current so it is better to use a buffer with a high impedance which then drives the LED.
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