Sync pin to SG3525 -IC used as MOSFET driver?

Thread Starter

Motanache

Joined Mar 2, 2015
481


With PWM signal in pin 4 Sync can work as MOSFET driver?

I have left the pins 5CT 6RT and 7Disc. unconnected.

In simulation with LTSpice it looks like it does not work and I do not understand the use of that pin.
The oscillator schematic is shown in the datasheet but I still did not understand the use of that pin.imgRCT.png
 

shortbus

Joined Sep 30, 2009
7,600
That sync pin is to allow more than one 3525 in a circuit to be driven at the same frequency/timing from one oscillator.

The chip it's self is normally used with Nmosfets, used as low side switches. In that configuration no gate driver is needed.
 

Thread Starter

Motanache

Joined Mar 2, 2015
481
That sync pin is to allow more than one 3525 in a circuit to be driven at the same frequency/timing from one oscillator.
I wish to see at least a schema with two SG3525 and a single oscillator.



The chip it's self is normally used with Nmosfets, used as low side switches. In that configuration no gate driver is needed.
Yes, I need 2 LOW Side Driver. But I think to use SG3525 as Low Side MOSFET driver it's not a good idea.

If anyone is interested I have the SG3525 model in LTSpice
 

shortbus

Joined Sep 30, 2009
7,600
From STMicro's web site. " A sync input to the oscillator allows multiple units to be slaved or a single unit to be synchronized to an external system clock."

From the same. "The output stages are totem-pole designs capable of sourcing or sinking" This is what a low side driver does.
The web page, http://www.st.com/en/power-management/sg3525.html
The device PDF data sheets will tell you all.
 

Kunlefemi

Joined Jan 23, 2020
4
Please house am new in the house, and I need some vital information on how to synchronize sg 3525ic. I mean how to use 2 or 3 of the ic together and control it with only 1 friqency
 

Kunlefemi

Joined Jan 23, 2020
4
Please house am new in the house, and I need some vital information on how to synchronize sg 3525ic. I mean how to use 2 or 3 of the ic together and control it with only 1 friquency.
I will be very happy if I can get some explanation or circuit diagram on it. Thanks in advance.
 

schmitt trigger

Joined Jul 12, 2010
201
It has been a loooooong time since I last did that, perhaps 35+ years.
If i remember correctly, you have to make the free running frequency lower than the synchronization frequency, as it works by discharging the timing cap earlier.
One side effect is that ramp amplitude will be lower.
The timing pulse also has to be narrow.
 

Kunlefemi

Joined Jan 23, 2020
4
It has been a loooooong time since I last did that, perhaps 35+ years.
If i remember correctly, you have to make the free running frequency lower than the synchronization frequency, as it works by discharging the timing cap earlier.
One side effect is that ramp amplitude will be lower.
The timing pulse also has to be narrow.
It has been a loooooong time since I last did that, perhaps 35+ years.
If i remember correctly, you have to make the free running frequency lower than the synchronization frequency, as it works by discharging the timing cap earlier.
One side effect is that ramp amplitude will be lower.
The timing pulse also has to be narrow.
Thanks for your quick response schmiyytrigger, but still not understand I need explanation on how to connect the pins together bot the input and output of the ic's
 

tsan

Joined Sep 6, 2014
116
There is more info about synchronous operation in SG2524 datasheet,
http://www.ti.com/lit/ds/symlink/sg2524.pdf

From the datasheet:
9.4.1 Synchronous Operation
When an external clock is desired, a clock pulse of approximately 3 V can be applied directly to the oscillator output terminal. The impedance to ground at this point is approximately 2 kΩ. In this configuration, RTCT must be selected for a clock period slightly greater than that of the external clock. If two or more SGx524 regulators are operated synchronously, all oscillator output terminals must be tied together. The oscillator programmed for the minimum clock period is the master from which all the other SGx524s operate. In this application, the CTRT values of the slaved regulators must be set for a period approximately 10% longer than that of the master regulator. In addition, CT (master) = 2 CT (slave) to ensure that the master output pulse, which occurs first, has a longer pulse duration and, subsequently, resets the slave regulators.
 

tsan

Joined Sep 6, 2014
116
There is a separate sync pin on SG3525, so outputs are not tied together. Connect oscilloscope output to to the sync pin on the next SG3525 and the oscillators operate in sync. This can be tested on LTspice simulator too.
 

Kunlefemi

Joined Jan 23, 2020
4
There is a separate sync pin on SG3525, so outputs are not tied together. Connect oscilloscope output to to the sync pin on the next SG3525 and the oscillators operate in sync. This can be tested on LTspice simulator too.
Thanks for the quick response tsan
There is a separate sync pin on SG3525, so outputs are not tied together. Connect oscilloscope output to to the sync pin on the next SG3525 and the oscillators operate in sync. This can be tested on LTspice simulator too.
Thanks for the quick response tsan, God bless you. I will go and try it and give you feedback on it.
Pls can I get your number or your email so that I can be contacting you.
 
Top