Sg3525 PWM Output

[mustafayilmaz]

I will use this integrated circuit to operate a motor with a 5-6 ampere maksimum current. The motor belongs to a spraying machine used in agriculture.

As far as I know, each output (Qa and Qb) can reach up to 50% duty cycle. For this reason, I am thinking of combining the outputs via a diode. Is there another method? I also want to understand whether a mosfet driver is needed. The pwm circuit will operate around 300-400Hz.

Another question is that a tiny switch potentiometer will be used to turn this circuit on and off. Since the power of the switch will not be able to handle large currents, I am thinking of turning the integrated circuit on and off directly. The gate leg of the mosfet will therefore be connected to chassis with a resistor. The existing circuit was a 555 circuit and was working with a tiny pot. Will this cause a problem?

[Andy Chee]

If you want 0-100% PWM duty cycle, you have selected the incorrect chip.

A better chip would be IR2153.

[David Hess]

Combining the outputs with two diodes or transistors will work, but then a driver might be required.  The SG3524 has uncommitted outputs which can be combined directly in parallel.

If you want 0-100% PWM duty cycle, you have selected the incorrect chip.

There is nothing wrong with combining the outputs to achieve >50% duty cycle, and it is even recommended in the application notes for this type of controller, although the SG3524 would be preferred.

[Xena E]

Hi Mustafa.

What about just using 2 mosfets each driven by its own Q output on the 3525 chip! Then parallel those to control the motor, they're cheap enough.

If the control voltage is within the capability of the gate of the pass mosfets then all you will need is a small (series) gate resistor, say 68ohm to stop fault propagation.

Just use your pot switch to switch the 3525, the power to the motor/mosfets need not be switched.

Regards
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