The **KA3525A** is a monolithic integrated circuit that includes all of the control circuitry necessary for a pulse width modulating (PWM) regulator. It is widely used in power supply control, DC-to-DC converters, and inverter designs. --- ## 1. Key Technical Specifications The following table outlines the fundamental electrical characteristics of the KA3525A: | Parameter | Value / Range | | :--- | :--- | | **Supply Voltage ($V_{CC}$)** | 8V to 35V | | **Output Current (Peak)** | ±500mA | | **Oscillator Frequency** | 100Hz to 400kHz | | **Reference Voltage ($V_{ref}$)** | 5.1V ± 1% | | **Operating Temperature** | 0°C to +70°C | | **Package Type** | 16-Pin DIP or SOP | --- ## 2. Internal Functional Blocks The KA3525A consists of several critical electronic sections: ### A. Voltage Regulator An internal 5.1V reference regulator provides a stable voltage for external circuitry and internal logic. It is accessible via **Pin 16**. ### B. Oscillator The frequency is determined by an external resistor ($R_T$) and capacitor ($C_T$). * **Formula:** $f \approx \frac{1}{C_T (0.7 R_T + 3 R_D)}$ * $R_D$ is a dead-time resistor used to prevent cross-conduction in power stages. ### C. Error Amplifier This is a differential amplifier (Pins 1 and 2) used to compare the feedback voltage from the output against the reference voltage to adjust the duty cycle. ### D. PWM Comparator and Latch This section converts the error signal into a PWM signal. The latch ensures that only one pulse is allowed per oscillator cycle, preventing multiple pulsing. ### E. Output Driver (Totem-Pole) The KA3525A features dual "Totem-Pole" output stages (Pins 11 and 14). This design allows the IC to both source and sink current, making it ideal for driving the gates of Power MOSFETs directly. --- ## 3. Pin Configuration | Pin No. | Name | Function | | :--- | :--- | :--- | | 1 | Inv. Input | Inverting input to the error amplifier. | | 2 | Non-Inv. Input | Non-inverting input to the error amplifier. | | 5 | $C_T$ | Timing capacitor for frequency setting. | | 6 | $R_T$ | Timing resistor for frequency setting. | | 8 | Soft Start | Connection for soft-start capacitor. | | 11 & 14 | Output A & B | PWM outputs (Out of phase by 180°). | | 13 | $V_C$ | Collector supply voltage for output stage. | | 15 | $V_{CC}$ | Main bias supply voltage. | --- ## 4. Basic Application Circuit (Code Example) While the KA3525A is an analog IC, its logic can be simulated or interfaced with microcontrollers. Below is a conceptual representation of how one might calculate the frequency in a design script: ```python def calculate_ka3525_freq(rt_ohms, ct_farads, rd_ohms=0): """ Calculates the approximate frequency of a KA3525A PWM controller. """ frequency = 1 / (ct_farads * (0.7 * rt_ohms + 3 * rd_ohms)) return round(frequency, 2) # Example: Rt = 10k, Ct = 1nF, Rd = 100 ohms print(f"Oscillator Frequency: {calculate_ka3525_freq(10000, 1e-9, 100)} Hz") ```