## Overview of the MP3373 The **MP3373** is a high-efficiency, step-up (boost) controller designed for large-sized Liquid Crystal Display (LCD) backlighting applications. It is specifically engineered to drive multiple strings of LEDs. --- ### 1. Key Internal Electronic Blocks The MP3373 integrates several functional blocks to manage power and protection: | Component Block | Function | | :--- | :--- | | **Step-up Controller** | Drives an external N-Channel MOSFET to boost the input voltage to the level required by the LED strings. | | **Current Sink Channels** | Contains 8 internal current sinks to balance current across multiple LED strings (up to 100mA per string). | | **PWM/Analog Dimming** | Manages brightness via Pulse Width Modulation or DC voltage adjustment. | | **Protective Circuitry** | Includes Over-Voltage Protection (OVP), Short-Circuit Protection, and Thermal Shutdown. | --- ### 2. Technical Specifications The following table summarizes the primary electrical characteristics of the MP3373: | Parameter | Value / Range | | :--- | :--- | | **Input Voltage ($V_{IN}$)** | 9V to 30V | | **Number of Channels** | 8 Channels | | **Maximum LED Current** | 100mA per channel | | **Switching Frequency** | Programmable (200kHz to 600kHz) | | **Feedback Voltage ($V_{FB}$)** | 400mV (Low headroom for high efficiency) | | **Package Type** | TSSOP28-EP, SOIC28 | --- ### 3. Pin Configuration Highlights To understand the electronic operation, the role of specific pins is crucial: * **GATE:** Connects to the gate of the external power MOSFET. * **LED1 - LED8:** Inputs for the LED cathode strings; these are the current sink terminals. * **COMP:** Compensation pin for the internal error amplifier to stabilize the control loop. * **OVP:** Monitors the output voltage; if the voltage exceeds a set threshold (e.g., an open LED string), the IC shuts down. * **ISET:** A resistor connected here sets the full-scale LED current. * **EN:** Enable pin to turn the chip on or off. --- ### 4. Application Circuit Logic The MP3373 operates using **Peak Current Mode Control**. 1. **Inductor Charging:** The GATE pin turns on the external MOSFET, storing energy in the inductor. 2. **Energy Transfer:** When the MOSFET turns off, the energy is released through a Schottky diode to the output capacitor, powering the LEDs. 3. **Current Regulation:** The IC monitors the voltage at the `LEDx` pins. It automatically adjusts the Boost output to ensure the string with the highest forward voltage has enough headroom, while minimizing power loss in the other strings. --- ### 5. Protection Features The MP3373 is highly robust due to its integrated logic: * **Open LED Protection:** If a string is disconnected, the OVP pin detects the voltage spike and disables the faulty channel. * **Short LED Protection:** If an LED string shorts, the IC detects the excess voltage at the `LEDx` pin and shuts down to prevent overheating. * **Under-Voltage Lockout (UVLO):** Prevents the device from operating if the input voltage is too low for stable switching.