KA3525A Controller Pinout, Test Circuit and Equivalents | Heisener Electronics
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KA3525A Controller Pinout, Test Circuit and Equivalents

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Post-datum: 2024-06-24, Fairchild/ON Semiconductor

KA3525A Introduction

The KA3525A is a pulse width modulation (PWM) controller. It integrates all the necessary circuitry to control a switching power supply in a single package, including a voltage reference, error amplifier, oscillator, pulse width modulator, and output driver. The KA3525A operates at fixed frequency, set by an external resistor and capacitor, and it includes features such as adjustable dead time control, soft-start circuitry. 

KA3525A Pinout

KA3525A CAD Model

Symbol

Footprint

3D Model

KA3525A Test Circuit

KA3525A Block Diagram

KA3525A Specifications

Here is a table listing the key specifications of the KA3525A PWM controller:

Specification Value
Voltage - Supply (Vcc/Vdd) 7 V - 20 V
Output Voltage 5.1V
Oscillator Frequency Adjustable up to 500kHz
Output Current 200mA (sink), 100mA (source)
Undervoltage Lockout 8V (typical)
Duty Cycle (Max) 49%
Dead Time Control Programmable
Current Limit Threshold Adjustable
Frequency - Switching 60Hz - 430kHz
Operating Temperature 0°C -70°C
Package DIP-16, SOP-16
Error Amplifier Gain 90dB
Shutdown Current 2mA (typical)
Typical Power Dissipation 1000mW
Short Circuit Protection Available
Sync Capability Yes

KA3525A Features

- Stable reference voltage of 5.1V ± 1%

- Source 100mA and sink 200mA

- The device includes an undervoltage lockout feature

- Soft start functionality and dead time control are programmable

- The current limit threshold is adjustable

- Supports an output duty cycle range from 0% to 100%

- The built-in error amplifier has a high gain of 90dB

- Features a low shutdown current of 2mA

- Short circuit protection

KA3525A Applications

Switching power supplies

DC-DC converters

Inverters

Battery chargers

Motor controllers

Uninterruptible power supplies (UPS)

Solar power inverters

Telecommunications power systems

Lighting systems

Industrial power controls

KA3525A Manufacturer

The KA3525A is manufactured by Onsemi, which provides high-performance, energy-efficient solutions for a range of applications, including automotive, communications, computing, consumer electronics, industrial, LED lighting, medical, and power supplies. 

KA3525A Package

The KA3525A is available in a 16-DIP (Dual In-line Package) configuration. The 16-DIP package consists of 16 pins arranged in two parallel rows, each with 8 pins. This layout facilitates straightforward insertion into corresponding PCB holes. 

KA3525A Equivalents

Component Manufacturer Output Current Input Voltage(Max) Switching Frequency(Max) Package Type
SG3525 Texas Instruments 500 mA 35 V 400 kHz 16-DIP, 16-SOIC
TL494 Texas Instruments 250 mA 40 V 300 kHz 16-DIP, 16-SOIC
UC3525 Texas Instruments 500 mA 35 V 400 kHz 16-DIP, 20-SOIC
MC3525 ON Semiconductor 500 mA 35 V 400 kHz 16-DIP, 16-SOIC
KA7500C ON Semiconductor 250 mA 40 V 200 kHz 16-DIP, 16-SOIC

How to Use KA3525A ?

To get started, connect the KA3525A in a standard application circuit. Begin by providing the power supply to the VCC pin (Pin 15). Connect a timing resistor and capacitor to the RT and CT pins (Pins 6 and 7) to set the oscillator frequency. The control voltage is applied to the inverting input of the error amplifier (Pin 2), while the non-inverting input (Pin 1) is typically connected to a reference voltage. The error amplifier compares the feedback voltage with the reference voltage and adjusts the output duty cycle accordingly. The outputs (Pins 11 and 14) are connected to the gates of external power transistors, which drive the load.

Then place a decoupling capacitor close to the VCC pin to filter out high-frequency noise. Additionally, protect the circuit from overcurrent conditions by connecting a current sense resistor and configuring the shutdown pin (Pin 10) to disable the output in the event of an overcurrent situation. 

FAQs

What precautions should be taken when designing with the KA3525A?

Ensure proper decoupling of the power supply to minimize noise.

Carefully design the feedback loop for stability.

Use appropriate heat sinking for the power transistors to prevent overheating.

Implement overcurrent protection to safeguard the power supply.

What is the function of the error amplifier in the KA3525A?

The error amplifier compares the feedback voltage from the output with a reference voltage and adjusts the PWM duty cycle to maintain a constant output voltage.

How does the shutdown feature work?

The shutdown pin (Pin 10) can be used to disable the output drivers in case of a faulty condition such as overcurrent or overvoltage. When the voltage on this pin exceeds a certain threshold, the internal logic disables the output to protect the circuit.

What types of feedback loops are compatible with the KA3525A?

The KA3525A supports both voltage feedback and current feedback loops. Voltage feedback is typically used for output voltage regulation, while current feedback can provide additional control for current limiting and improved transient response.

How do I configure the dead-time control on the KA3525A?

The dead-time control is set using a resistor between the dead-time control pin (Pin 4) and the ground. This resistor determines the minimum time interval between the turning off of one transistor and the turning on of the next in push-pull configurations to prevent short circuits.

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