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Designing and Building Switching Power Supplies with SG3525 PWM Circuit (PDF)


What is SG3525 and Why You Need It


If you are interested in designing or building switching power supplies, you may have come across the term SG3525. But what is it and why do you need it? In this article, we will explain what SG3525 is, how it works as a pulse width modulator, what are its features and benefits, and how you can download its application note pdf for more details and examples.




Sg3525 Application Note Pdf Download

How SG3525 Works as a Pulse Width Modulator


SG3525 is a pulse width modulator (PWM) integrated circuit that can be used to control the output voltage and current of switching power supplies. PWM is a technique that switches the power supply on and off at a high frequency, varying the duty cycle (the ratio of on-time to off-time) to adjust the output voltage and current. PWM can improve the efficiency, stability, and performance of switching power supplies. SG3525 has an internal oscillator that generates a clock signal for the PWM operation. The oscillator frequency can be adjusted from 100 Hz to 500 kHz by using an external resistor and capacitor. The oscillator also has a sync input that allows multiple SG3525 units to be synchronized or a single unit to be synchronized to an external system clock. SG3525 has an error amplifier that compares the feedback voltage from the output of the power supply with a reference voltage of 5.1 V. The error amplifier produces an error signal that controls the duty cycle of the PWM output. The error amplifier has an input common-mode range that includes the reference voltage, eliminating the need for external divider resistors. SG3525 has an adjustable deadtime control circuit that determines the minimum time between two consecutive PWM pulses. The deadtime can be programmed by using a single resistor connected between the CT and Discharge pins. The deadtime control can prevent cross-conduction and improve efficiency in switching power supplies. SG3525 also has built-in soft-start circuitry that gradually increases the duty cycle of the PWM output from zero to the desired value when the power supply is turned on. The soft-start circuitry requires only an external timing capacitor. The soft-start circuitry can prevent overshoot, undershoot, and stress in switching power supplies. SG3525 has a shutdown input that can turn off both the soft-start circuitry and the output stages, providing instantaneous turn off through the PWM latch with pulsed shutdown, as well as soft-start recycle with longer shutdown commands. The shutdown input can also be used for pulse-by-pulse current limiting or overvoltage protection in switching power supplies. SG3525 has an undervoltage lockout circuit that keeps the outputs off and the soft-start capacitor discharged for sub-normal input voltages. The undervoltage lockout circuitry has about 500 mV of hysteresis for jitter-free operation. SG3525 has dual source/sink output drivers that can deliver up to 400 mA peak current to drive MOSFETs or bipolar transistors in switching power supplies. The output drivers have NOR logic, giving a low output for an off state. Features and Benefits of SG3525


  • SG3525 has many features and benefits that make it a versatile and reliable PWM controller for switching power supplies. Some of the main features and benefits are: 8 to 35 V operation: SG3525 can operate from a wide range of input voltages, making it suitable for various applications.

  • 5.1 V reference trimmed to 1 %: SG3525 has an accurate and stable reference voltage that can be used for feedback and regulation.

  • 100 Hz to 500 kHz oscillator range: SG3525 can operate at different frequencies, allowing for trade-offs between efficiency, noise, and component size.

  • Separate oscillator sync terminal: SG3525 can synchronize multiple units or a single unit to an external system clock, enabling phase-shifted or interleaved operation for reduced ripple and noise.

  • Adjustable deadtime control: SG3525 can program the minimum time between two consecutive PWM pulses, preventing cross-conduction and improving efficiency.

  • Internal soft-start: SG3525 can gradually increase the duty cycle of the PWM output from zero to the desired value when the power supply is turned on, preventing overshoot, undershoot, and stress.

  • Pulse-by-pulse shutdown: SG3525 can turn off the PWM output for each cycle when the shutdown input is activated, providing fast and accurate current limiting or overvoltage protection.

  • Input undervoltage lockout with hysteresis: SG3525 can keep the outputs off and the soft-start capacitor discharged for sub-normal input voltages, ensuring safe and reliable operation.

  • Latching PWM to prevent multiple pulses: SG3525 has a latch following the comparator that prevents more than one PWM pulse per cycle, avoiding excessive switching losses and stress.

  • Dual source/sink output drivers: SG3525 can drive MOSFETs or bipolar transistors with high current and low impedance, ensuring fast and efficient switching.

Applications of SG3525 in Switching Power Supplies


  • SG3525 can be used in various types of switching power supplies, such as: Buck converter: A buck converter steps down the input voltage to a lower output voltage by switching a transistor on and off at a high frequency. The duty cycle of the transistor determines the output voltage. SG3525 can be used as a PWM controller for the transistor, providing feedback and regulation.

  • Boost converter: A boost converter steps up the input voltage to a higher output voltage by switching a transistor on and off at a high frequency. The duty cycle of the transistor determines the output voltage. SG3525 can be used as a PWM controller for the transistor, providing feedback and regulation.

  • Buck-boost converter: A buck-boost converter can either step down or step up the input voltage to a different output voltage by switching two transistors on and off at a high frequency. The duty cycle of the transistors determines the output voltage. SG3525 can be used as a PWM controller for the transistors, providing feedback and regulation.

  • Flyback converter: A flyback converter transfers energy from the input to the output by storing it in an inductor during the on-time of a transistor and releasing it during the off-time. The duty cycle of the transistor determines the output voltage. SG3525 can be used as a PWM controller for the transistor, providing feedback and regulation.

  • Forward converter: A forward converter transfers energy from the input to the output by using a transformer during the on-time of a transistor and blocking it during the off-time. The duty cycle of the transistor determines the output voltage. SG3525 can be used as a PWM controller for the transistor, providing feedback and regulation.

How to Download SG3525 Application Note Pdf


If you want to learn more about SG3525 and how to use it in your switching power supply projects, you may want to download its application note pdf. An application note is a document that provides technical information, design tips, examples, and circuits related to a specific product or topic. An application note pdf is a portable document format file that can be viewed, printed, or downloaded on any device. In this section, we will show you how to download SG3525 application note pdf from different sources. We will also provide you with some brief summaries of what you can find in each application note pdf. Sources of SG3525 Application Note Pdf


Article with HTML Formatting --- onsemi


  • onsemi is a semiconductor company that produces SG3525A, a pulse width modulator control circuit that offers improved performance and lower external parts count when implemented for controlling all types of switching power supplies. onsemi provides an application note pdf for SG3525A that covers the following topics: General description and features of SG3525A

  • Functional block diagram and pin connections of SG3525A

  • Typical application circuit and waveforms of SG3525A

  • Electrical characteristics and specifications of SG3525A

  • Design considerations and formulas for SG3525A

  • Example circuits and calculations for SG3525A

You can download the application note pdf for SG3525A from onsemi by clicking on this link or searching for "SG3525A-D.pdf" on their website. STMicroelectronics


  • STMicroelectronics is a semiconductor company that produces SG2525A and SG3525A, regulating pulse width modulators that are designed to offer improved performance and lowered external parts count when used in designing all types of switching power supplies. STMicroelectronics provides an application note pdf for SG2525A and SG3525A that covers the following topics: General description and features of SG2525A and SG3525A

  • Absolute maximum ratings and thermal data of SG2525A and SG3525A

  • Functional block diagram and pin connections of SG2525A and SG3525A

  • Electrical characteristics and specifications of SG2525A and SG3525A

  • Design considerations and formulas for SG2525A and SG3525A

  • Example circuits and calculations for SG2525A and SG3525A

You can download the application note pdf for SG2525A and SG3525A from STMicroelectronics by clicking on this link or searching for "SG3525.pdf" on their website. Other Websites


  • Besides onsemi and STMicroelectronics, there are also other websites that provide application note pdfs for SG3525 or similar products. Some of these websites are: Digi-Key: A distributor of electronic components that offers various application note pdfs for PWM controllers, such as "AN-4162 Designing an Isolated Buck (Step-Down) Converter.pdf". You can find these pdfs by searching for "PWM controller application note" on their website.

  • Texas Instruments: A semiconductor company that offers various application note pdfs for PWM controllers, such as "SLVA001E Switching Regulator Circuit Collection.pdf". You can find these pdfs by searching for "PWM controller application report" on their website.

  • ELECTRONICS TUTORIALS: A website that provides tutorials, articles, and projects on electronics topics, such as "SG3524 PWM Inverter Circuit". You can find these pdfs by searching for "SG3524" or "SG3525" on their website.

Steps to Download SG3525 Application Note Pdf


  • To download SG3525 application note pdf from any source, you can follow these simple steps: Choose a source: Decide which source you want to download the application note pdf from, based on your preference, availability, and relevance.

  • Click on the link or search for the pdf: If you have a direct link to the application note pdf, you can simply click on it to open or download it. If you don't have a direct link, you can search for the pdf on the source's website by using keywords such as "SG3525", "application note", or "pdf".

  • Save or open the pdf file: Once you find the application note pdf, you can either save it to your device or open it in your browser or a pdf reader. You can then view, print, or share the pdf file as you wish.

Conclusion


Summary of the Article


In this article, we have explained what SG3525 is, how it works as a pulse width modulator, what are its features and benefits, and how you can download its application note pdf for more details and examples. We have also provided you with two tables: one for the outline of the article and one for the article with HTML formatting. We hope that this article has been informative and helpful for you. FAQs


  • Here are some frequently asked questions about SG3525 and its application note pdf: Q: What is the difference between SG2525A and SG3525A?A: SG2525A and SG3525A are essentially the same product, except for the operating ambient temperature range. SG2525A can operate from -25 C to 85 C, while SG3525A can operate from 0 C to 70 C.

  • Q: What are some alternatives to SG3525?A: There are many other PWM controllers that can be used for switching power supplies, such as TL494, UC3842, UC3843, UC3844, UC3845, etc. You can compare their features and specifications to find the best one for your application.

  • Q: How can I design a switching power supply using SG3525?A: You can use the design considerations and formulas provided in the application note pdfs to design a switching power supply using SG3525. You can also refer to the example circuits and calculations provided in the application note pdfs or other sources to get some inspiration and guidance.

  • Q: How can I test and troubleshoot a switching power supply using SG3525?A: You can use an oscilloscope, a multimeter, a load tester, and other tools to test and troubleshoot a switching power supply using SG3525. You can also check the application note pdfs or other sources for some tips and techniques on how to test and troubleshoot a switching power supply using SG3525.

  • Q: Where can I find more information about SG3525?A: You can find more information about SG3525 by reading the datasheet, the application note pdfs, or other sources that we have mentioned in this article. You can also search online for more articles, tutorials, projects, or videos related to SG3525.

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