The **LM4040BIM3X-4.1/NOPB** is a precision micro-power shunt voltage reference. It functions similarly to a Zener diode but offers significantly higher stability and a much sharper turn-on characteristic. --- ### 1. Key Technical Specifications | Parameter | Value / Description | | :--- | :--- | | **Output Voltage** | 4.096 V (Fixed) | | **Tolerance** | ±0.2% (Grade B) | | **Package** | SOT-23-3 (Surface Mount) | | **Operating Current** | 73 µA to 15 mA | | **Temperature Coefficient** | 100 ppm/°C | | **Dynamic Impedance** | 0.8 Ω (Typical) | | **RoHS Status** | Pb-Free / NOPB (No Pb/Lead) | --- ### 2. Functional Details #### Shunt Configuration Unlike a series regulator (like the LM7805), a shunt reference operates in parallel with the load. It maintains a constant voltage by varying its internal resistance to "shunt" excess current to ground. This makes it highly versatile for creating negative voltage references or floating references. #### Part Number Breakdown * **LM4040**: The base model number (Shunt Voltage Reference). * **B**: Accuracy grade (B = 0.2% initial tolerance). * **I**: Industrial temperature range (-40°C to +85°C). * **M3**: Package code for SOT-23. * **X**: Indicates Tape & Reel packaging (usually 3000 units). * **4.1**: Represents the nominal voltage of 4.096V. * **NOPB**: Lead-free / RoHS compliant. --- ### 3. Typical Application Circuit To use this part, you must place a current-limiting resistor ($R_s$) between the input voltage ($V_{in}$) and the device. ```text V_in ----[ R_s ]----+---- Output (4.096V) | [LM4040] | GND ``` **Calculating $R_s$:** The resistor must be sized so that the current stays within the operating range (minimum 73 µA) while accounting for your load requirements: $$R_s = \frac{V_{in} - V_{out}}{I_{load} + I_{shunt}}$$ --- ### 4. Common Use Cases 1. **ADC Reference:** Providing a stable 4.096V reference for Analog-to-Digital Converters (where 1 bit often equals exactly 1mV in 12-bit systems). 2. **Precision Power Supplies:** Serving as the feedback reference for linear regulators. 3. **Instrumentation:** Calibration circuits for sensors and measurement devices. 4. **Battery Powered Gear:** Due to the low minimum operating current (73 µA), it is ideal for power-sensitive applications.