The **REF191** is a precision band gap voltage reference from the REF19x series, manufactured primarily by Analog Devices. It is designed to provide a stable, low-noise output voltage for high-accuracy electronic circuits. --- ### 1. Key Technical Specifications The REF191 is specifically known for its **2.048 V** output, which is a common value used to simplify calculations in Digital-to-Analog (DAC) and Analog-to-Digital (ADC) conversion. | Parameter | Value / Range | | :--- | :--- | | **Output Voltage** | 2.048 V | | **Input Voltage Range** | 3.0 V to 15 V | | **Output Current** | Up to 30 mA | | **Quiescent Current** | 45 $\mu$A (Typical) | | **Sleep Mode Current** | < 15 $\mu$A | | **Dropout Voltage** | 450 mV (at 10 mA load) | | **Package Options** | SOIC-8, TSSOP-8, PDIP-8 | --- ### 2. Core Functional Components The internal architecture of the REF191 consists of several critical stages: 1. **Band Gap Reference:** The "heart" of the chip that generates a stable voltage by utilizing the predictable thermal characteristics of silicon junctions. 2. **Error Amplifier:** Compares the feedback from the output to the band gap reference to maintain the exact 2.048 V level. 3. **Output Driver:** A high-current output stage capable of sourcing up to 30 mA, which is unusually high for a precision reference. 4. **Shutdown Pin (SLEEP):** Allows the device to be powered down via a digital signal, reducing power consumption to near-zero levels. --- ### 3. Application Use Cases Because of its high precision and low noise, the REF191 is found in: * **Precision ADCs:** 2.048 V is ideal for 12-bit converters, where 1 LSB (Least Significant Bit) equals exactly 0.5 mV. * **Portable Instrumentation:** Due to its low quiescent current and shutdown feature. * **Industrial Control Systems:** Used as a stable reference for sensors (pressure, temperature). * **Loop-Powered Systems:** Ideal for 4 mA to 20 mA transmitters. --- ### 4. Typical Circuit Connection Below is a basic representation of how the REF191 is wired in a standard circuit. ```mermaid graph LR Vin[Input Voltage 3V-15V] --> Pin2[Pin 2: Vin] GND[Ground] --> Pin 4[Pin 4: GND] Pin6[Pin 6: Vout] --> Load[Load / ADC Ref Pin] Pin3[Pin 3: Sleep] --> Logic[Control Logic] C1(1uF Capacitor) --- Pin6 ``` ---