The **LP3308** is a high-efficiency, constant frequency, current mode PWM step-up (boost) converter. It is widely used in portable devices to step up a lower battery voltage to a higher level required by components like LCD backlights or power rails. --- ### ## Technical Specifications | Parameter | Value/Range | | :--- | :--- | | **Input Voltage Range** | 2.2V to 6.0V | | **Output Voltage Range** | Up to 28V (Adjustable) | | **Switching Frequency** | 1.2 MHz | | **Switch Current Limit** | ~2.0A | | **Package Type** | SOT23-6 | | **Efficiency** | Up to 90% | --- ### ## Key Features and Internal Parts 1. **Power MOSFET:** It integrates a low $R_{DS(ON)}$ N-Channel MOSFET, which reduces the need for external power components and saves PCB space. 2. **Frequency (1.2 MHz):** The high switching frequency allows for the use of small-sized inductors and ceramic capacitors. 3. **Soft-Start:** Prevents inrush current during startup, protecting the battery and internal circuitry. 4. **Protection Circuits:** * **Over Temperature Protection (OTP):** Shuts down the chip if it overheats. * **Over Voltage Protection (OVP):** Prevents damage if the feedback loop is broken. * **Under Voltage Lockout (UVLO):** Ensures the chip only operates when the input voltage is sufficient. --- ### ## Application Circuit Components To build a functional circuit with the LP3308, you typically need the following external electronic parts: * **Inductor (L):** Usually 4.7µH to 22µH. It stores energy during the "ON" cycle of the switch. * **Schottky Diode (D):** A fast-switching diode (e.g., SS14) is required to rectify the output. * **Input/Output Capacitors ($C_{IN}, C_{OUT}$):** Ceramic capacitors (10µF - 22µF) are recommended for stability and low ripple. * **Feedback Resistors ($R_1, R_2$):** Used to set the output voltage via a voltage divider connected to the FB pin. ### ## Feedback Calculation The output voltage ($V_{OUT}$) is determined by the following formula: `Vout = 1.23V * (1 + R1 / R2)` ---