Author Topic: DALI TX opto should have greater CTR?  (Read 106 times)

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Offline treez

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DALI TX opto should have greater CTR?
« on: December 07, 2017, 07:42:36 AM »
Hello,
Figure 5, page 3, of the following DALI application note (AN1465) shows optos being used to isolate both TX and RX DALI signals…. :D

AN1465 Application note:
http://ww1.microchip.com/downloads/en/AppNotes/01465A.pdf

Though surely, the TX opto should be a TCLT1009 (CTR of TCLT1009 = 300%) and not a TCLT1000 (CTR of TCLT1000 = 50%)?   :-//

Also, surely the RX opto should be a TCLT1000, which it indeed is.  :clap:

The reason that the RX opto should be a TCLT1000 is because it has a lower capacitance seen at its emitter pin which means the rise time of the emitter can be quicker. Do you agree?  :-//

TCLT100X opto datasheet:
https://www.vishay.com/docs/83515/tclt1000.pdf
 

Offline CJay

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Re: DALI TX opto should have greater CTR?
« Reply #1 on: December 07, 2017, 07:54:55 AM »
DALI is only 1200BPS isn't it?

Not at all convinced it's necessary for it to be faster, I'm transferring 19200 BPS logic level serial through two CNY25s, the only extra components are a couple of pull up resistors per opto.
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