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#21 | |
diyAudio Member
Join Date: Feb 2003
Location: Bristol
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Quote:
why add a 10 watt resistor and effect the output, with a value of 0.01 ohms, when you can short it?
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If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked". |
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#22 | |
Account Disabled
Join Date: Apr 2003
Location: US
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Quote:
so you can set the current limit to protect your amp? |
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#23 | |
diyAudio Member
Join Date: Feb 2003
Location: Bristol
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Quote:
but in my case, i just wanted te max limit (0.01 ohms) this seems pointless to me.
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If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked". |
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#24 | |
Account Disabled
Join Date: Apr 2003
Location: US
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Quote:
I assume you wanted to be able to reach the 10A peak current output limit. The datasheet isn't clear as to if there is any protection if you short the current sensing resistor. My guess is no, as the datasheet mentioned nothing about thermal shutdown. If that is true, shorting the current sensing resistor may lead to permanent damage to the chip. |
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#25 |
diyAudio Member
Join Date: Jun 2002
Location: Portugal
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have you compared these chips with the LM3875?
Miguel |
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#26 |
diyAudio Member
Join Date: Feb 2003
Location: Bristol
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how can 0.01 ohms not cause damage, but 0 ohms can?
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If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked". |
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#27 | |
diyAudio Member
Join Date: Sep 2002
Location: Norway
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Quote:
if you check the datasheet's SOA chart you'll see that 0,01 ohm with any decent rail voltage can cause some smoke ![]() edit: or calculate it ![]()
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Mads K |
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#28 | |
Account Disabled
Join Date: Apr 2003
Location: US
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Quote:
the trigger seems to be a Vbe junction, per the TI schematics. that is confirmed by the formula used to calculate the current sensing resistor: Rcl=0.8/Icl-0.06 (or 0.02, depending which side of the cycle you are on). so a 0.01ohm resistor will limit the output current to 11A - 26A; while a 0phm resistor will limit the output current to 13A - 40A. as you can tell, if the current is large enough, it will make a significant voltage drop on a smaller resistor. more detailed infor can be found in a TI AN as well. the datasheet for 549 seems to indicate that it uses a different protection mechanism. |
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#29 |
diyAudio Member
Join Date: Jun 2004
Location: France
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Hi.
541 or 549 could be used as headphone amp? Thanks |
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