The **LED2000** is an 850 kHz fixed-frequency PWM step-down (buck) DC-DC converter specifically designed to operate as a precise constant current source for driving high-power LEDs. --- ## 1. Core Technical Specifications The device is engineered to handle wide input voltages while maintaining a very low feedback voltage to maximize efficiency. | Parameter | Specification | | :--- | :--- | | **Input Voltage Range** | 3.0V to 18V | | **Output Current** | Up to 3A | | **Switching Frequency** | 850 kHz | | **Feedback Voltage ($V_{FB}$)** | 100 mV (Low power dissipation) | | **Efficiency** | Up to 95% | | **Package** | HSOP8 / VFQFPN8 | --- ## 2. Key Internal Electronic Blocks The LED2000 integrates several functional circuits to ensure stable LED operation: ### A. PWM Controller & Oscillator The internal oscillator runs at **850 kHz**, allowing for the use of small surface-mount inductors and capacitors. The Pulse Width Modulation (PWM) logic adjusts the duty cycle to maintain the constant current required by the LED string. ### B. Power MOSFET It contains an internal high-side **P-channel MOSFET**. Because it uses a P-channel switch, the device does not require an external bootstrap capacitor, simplifying the PCB layout. ### C. Feedback Loop ($V_{FB}$) Unlike standard voltage regulators (which usually have a 1.2V feedback), the LED2000 has a reference of only **100 mV**. * **Purpose:** This significantly reduces the power wasted as heat in the current-sensing resistor ($P = I^2 \times R$). --- ## 3. Essential External Components To build a circuit around the LED2000, the following electronic parts are required: 1. **Inductor ($L1$):** Typically ranges from $3.3\mu H$ to $10\mu H$. It stores energy during the "ON" cycle and releases it during the "OFF" cycle. 2. **Catch Diode ($D1$):** A Schottky diode (e.g., STPS3L40) is required for the freewheeling current path when the internal MOSFET is off. 3. **Sense Resistor ($R_{SENSE}$):** This is the most critical part for setting the LED current ($I_{LED}$). * *Formula:* $R_{SENSE} = \frac{100mV}{I_{LED}}$ 4. **Input/Output Capacitors:** Ceramic MLCC capacitors are recommended for low ESR and high ripple current handling. --- ## 4. Dimming Capabilities The LED2000 supports two methods of controlling light intensity: * **Analog Dimming:** By applying a voltage to the specific control pins. * **Digital PWM Dimming:** By applying a PWM signal to the **DIM pin**. This allows for a high dimming ratio without shifting the LED's color temperature (chromaticty). --- ## 5. Protection Features The chip includes built-in safety mechanisms to prevent electronic failure: * **Overcurrent Protection (OCP):** Pulse-by-pulse current limiting. * **Thermal Shutdown:** Automatically turns off if the junction temperature exceeds $150^\circ C$. * **Soft Start:** Gradually increases the current to prevent inrush spikes during power-up.