## Overview of the LED2001 The **LED2001** is a high-efficiency monolithic step-down (buck) current source designed specifically to drive high-power LEDs. Manufactured by STMicroelectronics, it is widely used in automotive, industrial, and architectural lighting due to its compact size and integrated features. --- ### 1. Key Technical Specifications Below are the primary electrical characteristics of the LED2001: | Parameter | Value | | :--- | :--- | | **Input Voltage Range** | 3.0V to 18V | | **Output Current** | Up to 4A | | **Switching Frequency** | 850 kHz | | **Feedback Voltage ($V_{FB}$)** | 100 mV (high efficiency) | | **Package** | HSOP8 (Exposed Pad) | | **Duty Cycle** | Up to 100% | --- ### 2. Main Electronic Components (Internal & External) To understand how the LED2001 functions, we look at its internal architecture and the required external components. #### Internal Features * **Power MOSFET:** An integrated N-channel MOSFET with an $R_{DS(on)}$ of approximately 40m$\Omega$, which minimizes heat dissipation. * **Current Limit Circuitry:** Monitors the pulse-by-pulse current to protect the LED and the IC. * **Error Amplifier:** Compares the feedback voltage from the LED string to an internal 100mV reference to maintain constant current. * **Thermal Shutdown:** Automatically shuts off the device if the junction temperature exceeds $150^\circ C$. #### External Components Required 1. **Inductor ($L1$):** Filters the switching current. Usually between $2.2\mu H$ and $10\mu H$. 2. **Input Capacitor ($C_{IN}$):** A ceramic capacitor (e.g., $10\mu F$) to reduce input voltage ripple. 3. **Schottky Diode ($D1$):** Necessary for the "freewheeling" current path when the internal switch is off. 4. **Sense Resistor ($R_{SEL}$):** The most critical part for setting the LED current. It is calculated using: $I_{LED} = \frac{V_{FB}}{R_{SEL}} = \frac{0.1V}{R_{SEL}}$ --- ### 3. Pin Configuration | Pin | Name | Description | | :--- | :--- | :--- | | 1 | **VCC** | Input supply voltage. | | 2 | **BOOT** | Bootstrap pin; requires a capacitor to drive the high-side N-MOSFET. | | 3 | **DIM** | Digital dimming input. Logic high enables the device. | | 4 | **FB** | Feedback pin. Connected to the sense resistor to regulate current. | | 5 | **EN** | Enable pin. Used to turn the device on/off. | | 6, 7 | **SW** | Switching node connected to the inductor. | | 8 | **GND** | Ground and thermal dissipation path. | --- ### 4. Dimming Control The LED2001 supports **PWM (Pulse Width Modulation) Dimming** via the **DIM** pin. * By applying a PWM signal to this pin, the average current through the LED can be adjusted linearly. * This method is preferred over analog dimming because it maintains the color temperature (CCT) of the LED, as the "on" current remains constant. ---