SG3525 Frequency

microsim444 · 27th January 2009, 09:14 AM

What is the formula used to calculate the frequency for the SG3525?

That info was not provided in the Datasheet.

?

pjp · 27th January 2009, 10:07 AM

The formula is given in a footnote on page 4 of the ST SG3525 datasheet.

microsim444 · 28th January 2009, 07:01 AM

I had the wrong data sheet from www.alldatasheet.com

The one i have for the Motorola version!!

Thanks

N-Channel · 28th January 2009, 08:48 PM

Clock (oscillator) frequency is:

F = 1/{0.7 * 3[R(d)] * R(t) * C(t)}.

So if you have no deadtime resistor, R(d) drops out of the equation. Now, for a clock frequency of, say, 120kHz, if your R(t) = 3.6kW, then your C(t) would = 3300pF. F(osc) is actually 120.25kHz, but that's close enough.

Remember, the SG3525 is dual-ended, so your switching frequency is always one-half the clock frequency, so your F(sw) = 60kHz.

Hope this helps.

Regards,

Steve

rajudp · 9th April 2009, 03:43 PM

the frequency is 1/{( 0.7RT+3RD) * CT}

N-Channel · 9th April 2009, 07:05 PM

Oops! I guess I had the paranthesis-bracket-symbology a bit mucked up. Yes, Rd is multiplied by 3, and Rt is multiplied by 0.7

Apologies for the confusion.

Steve

27th January 2009, 09:14 AM	#1
microsim444 Account Disabled Join Date: Oct 2008	SG3525 Frequency What is the formula used to calculate the frequency for the SG3525? That info was not provided in the Datasheet. ?

28th January 2009, 07:01 AM	#3
microsim444 Account Disabled Join Date: Oct 2008	Sheet I had the wrong data sheet from www.alldatasheet.com The one i have for the Motorola version!! Thanks

28th January 2009, 08:48 PM	#4
N-Channel diyAudio Member Join Date: Mar 2003 Location: Sol System	Clock (oscillator) frequency is: F = 1/{0.7 * 3[R(d)] * R(t) * C(t)}. So if you have no deadtime resistor, R(d) drops out of the equation. Now, for a clock frequency of, say, 120kHz, if your R(t) = 3.6kW, then your C(t) would = 3300pF. F(osc) is actually 120.25kHz, but that's close enough. Remember, the SG3525 is dual-ended, so your switching frequency is always one-half the clock frequency, so your F(sw) = 60kHz. Hope this helps. Regards, Steve __________________ -. ---.. -..- ---

9th April 2009, 07:05 PM	#6
N-Channel diyAudio Member Join Date: Mar 2003 Location: Sol System	Oops! I guess I had the paranthesis-bracket-symbology a bit mucked up. Yes, Rd is multiplied by 3, and Rt is multiplied by 0.7 Apologies for the confusion. Steve __________________ -. ---.. -..- ---

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

27th January 2009, 10:07 AM	#2
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	The formula is given in a footnote on page 4 of the ST SG3525 datasheet.

9th April 2009, 03:43 PM	#5
rajudp diyAudio Member Join Date: Mar 2005 Location: Kerala	the frequency is 1/{( 0.7RT+3RD) * CT}

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Synchronizing SG3525	Pierre	Power Supplies	17	17th March 2009 08:32 AM
SG3525, SMPS need help	jegandren	Power Supplies	12	12th September 2008 03:10 PM
SG3525 problem	lorenzo_cy	Power Supplies	7	19th April 2007 06:42 AM
SG3525 problem	ifrythings	Power Supplies	30	15th March 2007 06:11 PM
SG3525 - Getting started...	Wynand	Power Supplies	8	26th February 2007 02:25 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read