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Old 7th July 2011, 12:35 PM   #1
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Default IRS2092 CSH

hello there, i had some question about the current sensing of the floating driver.
everything is refered to irf typical diagram

The tension is aquired between CSD and Vs, fine, but what is the reference, and why did they use a different diode (bav19ws) between VB+ and CSH? I guess it is for aquiring signal only when the Ho is on.. but what is the cause of the choice; is it because of dark current?

i'll surly have some more questions after that, thx for further explanation guys!
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Old 8th July 2011, 08:26 PM   #2
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The diode needs to be fast because the class d frequency can be hundreds of KHz.
I use an stth1r02 diode for both fast diode components.

I split the CSD signal with two 4k7 resistors and found that to be good enough for a 500 watt amp into 4 ohms.
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Old 12th July 2011, 02:04 PM   #3
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you mean a 4,7k from Vs to CSH then a 4,7k with a diode to VB+ ?
and is the mur120 ( trr = 25ns) could do the job or the 15ns form your stth1r02 is greatly wished? also, the mur120 has a bigger leaking current, (double time) could this cause problem with sensing ?
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Old 12th July 2011, 08:13 PM   #4
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>you mean a 4,7k from Vs to CSH then a 4,7k with a diode to VB+ ?
Yes.


>and is the mur120 ( trr = 25ns) could do the job or the 15ns form your >stth1r02 is greatly wished? also, the mur120 has a bigger leaking current, >(double time) could this cause problem with sensing ?[/QUOTE]

I havent tried a mur120 so cant speak for that but the stth works fine.
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Old 12th July 2011, 11:53 PM   #5
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allright, im gonn put a var-res for first pcb proto, thanks
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Old 13th July 2011, 12:21 AM   #6
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Quote:
Originally Posted by philuknow View Post
allright, im gonn put a var-res for first pcb proto, thanks
Remember OCSET sets the over current for the lower mosfet so might be worth putting in a preset there too.
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Old 13th July 2011, 10:02 PM   #7
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yeah i know I read all the AN-1138. though in the reference design they but a res between the anode of the diode and HO, for biasing the diode, is it needed ?

http://www.irf.com/technical-info/appnotes/an-1138.pdf
page 11, last sentence
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Old 13th July 2011, 10:07 PM   #8
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Originally Posted by philuknow View Post
yeah i know I read all the AN-1138. though in the reference design they but a res between the anode of the diode and HO, for biasing the diode, is it needed ?

http://www.irf.com/technical-info/appnotes/an-1138.pdf
page 11, last sentence
Yes it is needed as per reference datasheet.
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