Introduction to SG3525
Introduction to SG3525
- SG3525 is a pulse width modulated control circuit that is used to control switching power supplies and particularly helps in providing lower external parts count and improved performance.
- It is voltage control PWM controller in which feedback voltage is compared with reference value which then controls the duty cycle of PWM.
- It is mainly used in inverter applications and utilizes two main PWM outputs that are inversion of each other.
- The on-chip +5.1 reference is modified to ±1% and the error amplifier that comes with both input common mode voltage range and reference voltage, helps in terminating the need of external resistors.
- A sync input provided to the oscillator helps in synchronizing single unit to the external system clock.
- A single resistor existed between the discharge pins and Ct is used to program the wide range of deadtime.
- This modulator is also incorporated with built-in-soft start-circuitry which needs external timing capacitor.
- A shutdown pin is used to control both output stages and soft-start circuitry that also features instantaneous turn-off with the help of PWM latch and pulsed shutdown.
- When Vcc stays below nominal, the under voltage lockout limits both soft-start capacitor and outputs.
- The output stage of this modulator exhibits NOR logic and is similar to totem-pole design which makes it stand out from other ICs.
SG3525 Pins
- SG3525 is a 16 pin integrated circuit. Following figure shows the pin number along with their pin names.
SG3525 Pin Description
- SG3525 is a 16 pin IC. Each pin is allocated with different function.
- Following figure shows the pin number, pin name and functions associated with each pin.
- Soft start and compensation terminals receive the pull down signal and turn off the outputs when it sinks a maximum of 100µA current.
- There is another way of turning off the output which involves the shutdown circuitry of pin 10 that comes with an added amount of shutdown options.
- This circuit is activated by providing positive signal at the pin 10 which then executes two functions i.e. output signal turns off by immediately setting PWM latch and soft-start capacitor starts to discharge during the availability of 150 µA current.
- If the shutdown command is applied for short period of time, the PWM signal will be eliminated without discharging soft-start capacitor significantly, helps in carrying out pulse by pulse current limiting.
- However, if pin 10 is hold for longer duration will discharge the external capacitor quickly.
SG3525 Features
- 8V to 35V Operation
- 5.1V ± 1.0% Trimmed Reference
- Separate Oscillator Sync Pin
- 100 Hz to 400 kHz Oscillator Range
- Input Undervoltage Lockout
- Adjustable Deadtime Control
- Pulse-by-Pulse Shutdown
- Dual Source/Sink Outputs
- Latching PWM to Prevent Multiple Pulses
SG3525 Pinout
- Pinout diagram features proper and detailed configuration of any electronic device.
- SG3525 pinout diagram is shown in the figure below which elaborates the configuration of each pin of this modulator.
SG3525 Block Diagram
- Block diagram is described in schematic form which features the general arrangement of parts or elements used in the device or process.
- Following figure shows the block diagram of SG3525.
- It is clear from the figure that output stage of this modulator represents NOR logic.
Absolute Maximum Ratings of SG3525
- Following figure shows the absolute maximum ratings of SG3525.
- Supply voltage and collector supply voltage is 40 V.
- Maximum power it can dissipate is 1000 mW.
- It is important to note that if stresses are exceeded above absolute maximum ratings, they can damage the device ultimately.
- Similarly, if stresses are applied for maximum period of time, they can effect the device reliability.
Applications
- SG3525 has a wide range of applications but it is mainly used in transformer DC-DC inverters.
- It is used for regulating power supply.
- This modulator is useful for switching regulators of any polarity.
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