1. Overview & Functionality

· What is it? The AD586 is a high-precision, monolithic 5V voltage reference.
· Purpose: It provides a stable and accurate reference voltage for various precision circuits (e.g., ADCs, DACs).
· Key Features:
* Initial offset < 2.0 mV
* Temperature coefficient < 2 ppm/°C
* Requires minimal external components.

2. Theory of Operation & Design

· Internal Components: Consists of a buried Zener diode reference, a buffer amplifier, and high-stability thin-film resistors.
· Noise Reduction: An optional noise reduction filter can be implemented using an external capacitor connected to Pin 8 (Noise Reduction).
· Fine Trim: An optional external trim circuit can be used to adjust the output voltage up to ±300 mV.

3. Noise Performance

· Dominant Noise Source: The buried Zener diode contributes the most noise (~100 nV/√Hz).
· Typical Noise Levels:
* 0.1 Hz to 10 Hz: ~4 µV p-p
* 1 MHz: ~200 µV p-p
· Noise Reduction with Capacitor: Using a 1µF capacitor at Pin 8 reduces broadband noise (to 1 MHz).

4. Turn-on Characteristics

· Turn-on Time: The time it takes for the output to stabilize after power-up. It's influenced by active circuit settling and thermal stabilization.
· Typical Turn-on Time:
* Without capacitor: ~60 µs to 0.01%
* With 1 µF capacitor: ~400 ms to 0.01%

5. Dynamic Performance

· Load Regulation: The AD586's output buffer amplifier provides good static and dynamic load regulation.
· Importance: Good load regulation is important for applications where the reference is driving converters (ADCs/DACs) that present transient current loads.

6. Pin Descriptions

· Pin 1 & 3 & 7: Factory test points – *Do Not Connect*.
· Pin 2: Input Voltage
· Pin 4: Ground
· Pin 5: Optional External Fine Trim
· Pin 6: Output Voltage
· Pin 8: Optional Noise Reduction Filter (connect to ground via a capacitor)

Key Takeaways/Important Notes:

· The AD586 is a straightforward device to use, but careful consideration should be given to noise reduction and turn-on time, especially in sensitive applications.
· The optional external components (trim capacitor) have an impact on the circuit performance; these must be evaluated when designing a circuit to include the AD586.