smps - how do i set the sg3525 oscillator to 96khz

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tsuma

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smps need help

how do i set the sg3525 oscillator to 96khz to be used in an smps push pull topology
 

Re: smps need help

96kHz means a period of about 10us. So you look at the graph for the oscillator charge time and select an RT, CT pair that gives you about 10us of charge time. We will assume that the discharge time is much lower and anyway your frequency is slightly below 100kHz (period slightly above 10us), so you should be OK.

From the graph you can see that a 2.2nF cap and a 6.8K resistor should bring yuo close to 96Khz. Use these values as a starting piont with RD=0. Then change RT as needed to obtain a frequency as close to 96kHz as possible
 
Re: smps need help

thankyou ,the settings worked well. i still get another problem though inthe design.
how does one calculate the values of the capacitor and resistor of the input snubber. i find this snubber on practically all schematics but they dont give a way of calculating its values
 

Re: smps need help

the formula for oscillation is F=1/((0.7RT +3RD )xCT)

Where f is in HZ
RT is Timing Resister
RD is DEAD TIME Resister
CT is timing Capacitor

for push pull applications the Pwm is half of the oscilator fequency
according to the above values the frequency will be 95.49 KHz

Added after 5 minutes:

please check the maxim application note
 
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    bvale

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