### VRE202MA: Precision Voltage Reference The **VRE202MA** is a high-precision, low-noise voltage reference typically manufactured by Apex Microtechnology. It is designed for applications requiring extreme stability, such as high-resolution Data Acquisition Systems (DAS) and precision instrumentation. --- ### 1. Key Technical Specifications The "MA" suffix typically denotes a high-grade military or industrial temperature range with tighter tolerances. | Parameter | Typical Value | | :--- | :--- | | **Output Voltage** | +2.048 V | | **Initial Accuracy** | ±0.20 mV (max) | | **Temperature Coefficient** | 1.0 ppm/°C (max) | | **Input Voltage Range** | +13.5 V to +22.0 V | | **Output Current** | ±10 mA | | **Operating Temperature** | -55°C to +125°C | | **Package Style** | 20-pin LCC or 14-pin DIP | --- ### 2. Internal Construction and Features The VRE202MA utilizes a sophisticated internal architecture to achieve its performance: * **Zener-Based Reference:** It uses a buried (subsurface) Zener diode, which offers better long-term stability and lower noise compared to bandgap references. * **Laser Trimming:** The internal thin-film resistors are laser-trimmed to ensure the output voltage is exactly 2.048V and to minimize temperature drift. * **Heated Substrate:** Some models in this series use an internal heater to maintain a constant die temperature, effectively isolating the reference from ambient thermal fluctuations. * **Low Noise:** It features extremely low noise (typically < 1.5 µV p-p in the 0.1Hz to 10Hz range), essential for 16-bit to 24-bit ADCs. --- ### 3. Pin Configuration (Common 20-Pin LCC) While always check the specific datasheet, the standard layout for the VRE200 series involves: | Pin Number | Function | Description | | :--- | :--- | :--- | | 1 | NC | No Connection | | 2 | **V_IN** | Input Power Supply | | 8 | **V_OUT** | 2.048V Reference Output | | 10 | **GND** | System Ground | | 20 | **TRIM** | Optional fine-tuning of the output | --- ### 4. Typical Applications * **High-Resolution ADCs:** Specifically designed to provide a reference for 16-bit, 18-bit, and 24-bit converters. * **Medical Equipment:** Used in MRI or precision diagnostic tools where signal integrity is critical. * **Aerospace & Defense:** Due to the wide operating temperature and high stability. * **Calibration Standards:** Used as a local reference for laboratory-grade measurement equipment. --- ### 5. Implementation Considerations 1. **Bypassing:** Use high-quality tantalum and ceramic capacitors (e.g., 10µF and 0.1µF) on the input and output pins to minimize noise and ensure stability. 2. **Thermal Management:** Ensure the PCB layout minimizes heat transfer from power components to the VRE202MA to maintain its ppm-level accuracy. 3. **Loading:** While it can source/sink 10mA, for maximum precision, the load should be kept constant.