**High-Precision Voltage Reference Design Using the AD586TQ Quartz-Stabilized IC**
The pursuit of precision in electronic systems, particularly in instrumentation, data acquisition, and metrology, hinges on the stability and accuracy of the voltage reference. A poorly designed reference can introduce significant errors, undermining the performance of even the most sophisticated analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). This article details a high-performance voltage reference design centered on the **AD586TQ, a quartz-stabilized buried-zener voltage reference IC**, renowned for its exceptional precision.
**The Core Component: AD586TQ IC**
The AD586TQ is not a standard voltage reference. Its defining feature is an **on-chip quartz crystal** that synchronizes a dedicated internal oscillator. This oscillator drives the heating element for the reference's core zener diode, maintaining it at a constant, elevated temperature. This **active temperature stabilization** effectively eliminates the primary cause of drift in precision circuits: fluctuations in ambient temperature. The result is unparalleled stability with an initial accuracy of ±0.004% (±0.4mV), a temperature coefficient as low as **0.5 ppm/°C**, and long-term stability of 15 ppm/1000 hours.
**Critical Design Considerations**
While the AD586TQ provides a superb foundation, a robust design requires careful attention to the supporting components and layout.
1. **Power Supply Conditioning:** The IC's performance is directly linked to the quality of the input supply voltage. Any noise or ripple on the supply rail will be reflected on the output. Therefore, **localized decoupling is paramount**. A combination of a 10µF tantalum capacitor and a 0.1µF ceramic capacitor should be placed as close as possible to the V+ and GND pins of the IC. For applications demanding the utmost noise performance, a low-dropout regulator (LDO) can be used to pre-regulate the supply.
2. **Output Buffer and Trimming:** The AD586TQ can source up to 10mA, but loading it directly can induce errors. For driving dynamic loads or multiple devices, a **high-precision, low-noise operational amplifier** in a voltage-follower configuration is recommended as a buffer. This preserves the reference's characteristics while providing a low-impedance output. The IC features a dedicated trim pin (TRIM) for fine adjustment of the output voltage. This adjustment should be performed using a high-stability, multi-turn potentiometer to avoid introducing additional drift.
3. **PCB Layout for Precision:** A high-precision circuit demands a meticulous PCB layout. The design must prioritize:
* **A solid ground plane** to minimize ground loops and provide a stable reference.
* **Short, direct traces** for the critical signal path between the reference output, the trim network, and the buffer amplifier.
* **Thermal Symmetry:** Placing the IC away from heat-generating components (e.g., power regulators, resistors) is crucial to prevent external thermal gradients from defeating the purpose of the internal oven.
**Application Advantages**
Implementing a voltage reference with the AD586TQ is particularly advantageous in systems requiring the highest level of DC accuracy. It is the ideal choice for **16-bit and above ADC/DAC systems**, precision calibration equipment, laboratory standard instruments, and scientific measurement devices where performance must be maintained over a wide industrial temperature range.
**ICGOODFIND**
The **AD586TQ** stands as a benchmark for precision voltage references, offering designers a proven and reliable solution for achieving sub-ppm-level stability. Its integrated oven-controlled oscillator simplifies the design of ultra-stable reference circuits, making it an indispensable component for the most demanding measurement and conversion applications.
**Keywords:**
1. **Voltage Reference**
2. **Precision**
3. **Quartz-Stabilized**
4. **Temperature Coefficient (TC)**
5. **Buried-Zener**
