Activating this circuit by applying a positive OSCILLATOR SECTION (Note 5, unless otherwise noted.) Input Threshold, Maximum Duty Cycle (Note 5). Vth. −. Activating this circuit by applying a positive OSCILLATOR SECTION (Note 6, unless otherwise noted.) Input Threshold, Maximum Duty Cycle (Note 6). Vth. –. Free Application Note Power Supply And Power Management SG AN semiconductor datasheets. Datasheet search.


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The datasheet for these chips contains almost no application information.


Some sg3525 application note a small section detailing how the "Shutdown" pin can be used to skip a pulse when needed, but others don't even have that. The internet isn't much help either.

  • UCA Regulating Pulse Width Modulators |
  • Search and Download Electronic Component Datasheets.

Tahmid's blog has a pin-by-pin functional description with a demonstration sg3525 application note, and the SGx App Note describes a related chip, but with important differences.

If you don't understand something here, take a look at Tahmid's blog for a counterpoint explanation.

Using the UC3525 pulse width modulator

The output will be high when the triangle is higher than the reference and low everywhere else. Adjusting the reference adjusts the pulse width. Sg3525 application note UC chip is basically a triangle wave generator and comparator, with some extras thrown in for convenience.

Any properly-scaled voltage proportional to output error can be used as a reference voltage to the comparator.

Using the UC pulse width modulator | Details |

A larger error results in a higher reference voltage, which clips the triangle wave higher, which makes the output pulses narrower, which generates less output, which in turn generates a lower error voltage. For example, a 12V power supply might sg3525 application note an error voltage proportional to the difference between 12 volts and the actual output.

The voltage will shorten or lengthen the PWM times, forcing the output to exactly 12 volts. The circuit doesn't have to be a power supply, it only needs a feedback voltage proportional to the error.

To run a DC motor at a specific speed, simply feed back a voltage proportional to the difference between the requested speed and the actual speed: So for another example, you can make a class-D amplifier using an audio signal as Vref: Precision voltage source The UC supplies a precision 5.

Application Note Power Supply And Power Management SG AN Datasheet

For other sg3525 application note, simply generate 5. An example from Tahmid's blog: Error Amplifier The UC implements an extra op-amp on the VRef input of the comparator and brings the connections out to the user. This makes it easy to convert error signals - the positive input can level shift, while the inverting input and feedback can amplify the error to bring it into range.

You can also use the op-amp to slow down the feedback. In the circuit below, the PWM error adjustment is delayed by the RC constant of the amplifier feedback. This can eliminate ringing and spurious oscillations that you might get from instantaneous feedback. The control circuit is then isolated from the output.

Triangle wave sg3525 application note So a natural question to ask is: You start with a constant current source.

SG - Voltage Mode PWM - STMicroelectronics

Then you connect the constant current source to sg3525 application note constant capacitance and the voltage rises linearly as a function of time. The UC provides a constant sg3525 application note source and a flip-flop mechanism that alternately charges and discharges a capacitor which the user supplies.

The user also supplies an external resistor which sets the amount of current.