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tom_hanks
Joined: 28 Aug 2003
Posts: 256
Helped: 14
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 16 May 2007 16:08 7.2v lm723 |
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Hi there,
Can any one suggest the method to stablise the programmable ouput voltage..
ciruit is using I2C POT to change the voltage in between...12V,24V & 30V...with i/p:48V..
I am not getting stable o/o vge...
TIA,
tom
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melc
Joined: 08 Apr 2005
Posts: 394
Helped: 45
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16 May 2007 19:15 Re: programmable output voltage ??? |
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You need a negative feedback. Program via i2c the reference voltage and/or the R divisor network from the supply output. For understanding how can be done with a linear regulator, take only as example how is dimensioned the feedback network of the LM723 (which has 7.2V reference) for big output voltages.
For 12/24/30V the simplest way is to use a LM317 (supplied at max 35V) if you don't sink some large current. Note the quite high voltage that your I2C resistor must run if it's mounted at the output regulator resistor network. Do not exceed the datasheet limits.
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tom_hanks
Joined: 28 Aug 2003
Posts: 256
Helped: 14
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16 May 2007 21:28 Re: programmable output voltage ??? |
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hi there,
thanks for reply....
I am getting required voltage with Lreg & digitap POT...
problem is stability and tolerace....
application wants 5-10% Tol and good stability....
controller is scanning the supply every 100ms....to check in valid range...
i am looking for some suggestion to use after the POT circuit..like zener diode...
ready to donates the points.....50/100
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tom_hanks
Joined: 28 Aug 2003
Posts: 256
Helped: 14
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23 May 2007 16:16 Re: programmable output voltage ??? |
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i recieved one of the following suggestion....
"One moment can be the parasitic inductance of the output capacity, which is sensible against voltage spikes of the output switch.
Use low inductance capacities and keep the lead distance short.
"
but still not usefull to system...
any more i/p? are welcum
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