The **CS1365F** (often part of a series like the CS1365/CS1367) is a high-performance, highly integrated **Current Mode PWM Controller** designed specifically for offline AC/DC flyback converter applications. It is commonly found in power adapters, battery chargers, and open-frame switching power supplies (SMPS). --- ## 1. Key Technical Specifications | Parameter | Typical Value | Description | | :--- | :--- | :--- | | **Package Type** | SOP-8 / DIP-8 | Standard 8-pin small outline or dual in-line package. | | **Startup Current** | Low (approx. 5-20µA) | Minimizes power loss during the power-on phase. | | **Operating Frequency** | 65kHz (Fixed) | Standard frequency with built-in frequency shuffling for EMI. | | **Max VDD Voltage** | 25V - 30V | High voltage tolerance for the supply pin. | | **Protection Modes** | OVP, OLP, SCP, OTP | Comprehensive safety features for power stability. | --- ## 2. Core Functional Blocks The CS1365F integrates several critical sub-circuits to manage power conversion efficiently: 1. **Frequency Shuffling:** It slightly oscillates the switching frequency to spread Energy Interference (EMI) across a wider spectrum, allowing the device to pass electromagnetic compatibility tests with smaller filters. 2. **Extended Burst Mode Control:** At no-load or light-load conditions, the IC enters "Burst Mode" to reduce switching loss, helping the device meet global "Green Energy" standby power standards (usually <0.1W). 3. **Current Mode Control:** Uses a cycle-by-cycle current limiting mechanism to protect the MOSFET and transformer from saturation. 4. **Internal Slope Compensation:** Prevents sub-harmonic oscillations when the duty cycle exceeds 50%. --- ## 3. Pin Configuration and Functions | Pin Number | Name | Description | | :---: | :--- | :--- | | 1 | **GND** | Ground reference for the IC. | | 2 | **FB** | Feedback input. Connected to an optocoupler to regulate output voltage. | | 3 | **RI** | Internal Oscillator setting. Determines the switching frequency. | | 4 | **SENSE** | Current sense input. Connects to a resistor in series with the MOSFET source. | | 5 | **VDD** | Supply voltage for the IC. | | 6 | **GATE** | Totem-pole output to drive the gate of the external Power MOSFET. | --- ## 4. Typical Application Diagram Structure In a standard circuit, the CS1365F acts as the "brain": * **Input Side:** Rectified AC mains (DC High Voltage) provides a startup current via a resistor to the **VDD** pin. * **Switching Side:** The **GATE** pin toggles an N-channel MOSFET on and off at 65kHz. * **Regulation Side:** An optocoupler (e.g., PC817) sends a signal to the **FB** pin based on the secondary output voltage, allowing the IC to adjust the pulse width (PWM). ---