The **MP33** is a specialized electronic component, specifically a **High-Efficiency Step-Up (Boost) Converter** designed by Monolithic Power Systems (MPS). It is primarily used to drive white LED strings, typically for backlighting in small to medium-sized LCD panels (like those in handheld devices or instruments). --- ### 1. Key Technical Specifications Below are the primary electrical characteristics of the MP33: | Feature | Specification | | :--- | :--- | | **Input Voltage Range** | 2.7V to 6V | | **Output Voltage (Max)** | Up to 25V | | **Switching Frequency** | ~1.3 MHz | | **Feedback Voltage** | 0.2V (Low voltage to reduce power loss) | | **Efficiency** | Up to 90% | | **Package Type** | SOT23-6 or TSOT23-6 | --- ### 2. Core Internal Components The MP33 integrates several functional blocks into a single 6-pin chip: 1. **Internal Power MOSFET:** A low-resistance N-Channel MOSFET that acts as the main switch to build up energy in the external inductor. 2. **Current Mode Control:** Uses a fixed-frequency peak current mode to provide fast transient response and easy loop compensation. 3. **Soft-Start Circuit:** Prevents high inrush currents during startup to protect the battery and the chip. 4. **Over-Voltage Protection (OVP):** Protects the device if the LED string becomes open-circuit (preventing the output voltage from rising to destructive levels). 5. **Under-Voltage Lockout (UVLO):** Ensures the chip shuts down if the input voltage is too low for stable operation. --- ### 3. Required External Components To function as a complete boost converter circuit, the MP33 requires the following external parts: * **Inductor (L):** Usually 4.7µH to 22µH. It stores energy when the internal switch is ON and releases it to the LEDs when the switch is OFF. * **Schottky Diode (D):** Prevents current from flowing back from the output to the switch. High-speed switching is required. * **Input/Output Capacitors (Cin/Cout):** Ceramic capacitors (X5R or X7R) to filter noise and stabilize the voltage. * **Feedback Resistor (Rfb):** Sets the LED current. The chip maintains 0.2V across this resistor ($I_{LED} = 0.2V / R_{fb}$). --- ### 4. Pin Configuration | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **SW** | Power Switch Output. Connected to the inductor and Schottky diode. | | 2 | **GND** | Ground. | | 3 | **FB** | Feedback Input. Regulates the LED current. | | 4 | **EN** | Enable/Dimming Input. High = On, Low = Off. Can use PWM for dimming. | | 5 | **OVP** | Over-Voltage Protection sense pin. | | 6 | **IN** | Input Supply (2.7V - 6V). | --- ### 5. Application Circuit Diagram (Conceptual) ```text [Input Vin] ---- [Inductor] ----+---- [Schottky Diode] ---- [LED String] ---+ | | [Pin: SW] [Pin: FB] | [Resistor to GND] ``` ---