Power management
Voltage Reference
Stable, low-noise voltage source for ADCs, DACs, and precision analog circuits.
What is it?
A voltage reference is a precision IC that outputs a stable voltage (e.g., 1.25 V, 2.5 V, 4.096 V) across temperature, time, and load variation. Used wherever measurement accuracy matters, ADC reference input, DAC output scaling, comparator threshold setting. Better than using the supply rail (which moves with battery / regulator), better than a Zener (drifts with temperature).
When do you need it?
- ADC reference input (the accuracy of your measurement is bounded by the reference accuracy).
- DAC full-scale reference.
- Precision current source / sink circuits.
- Power-supply over-voltage / under-voltage threshold setting.
- Sensor excitation voltage where ratiometric measurement isn't possible.
How to pick the right one
- Output voltage
- Common: 1.25 V, 2.048 V, 2.5 V, 3.0 V, 4.096 V, 5.0 V. Match to your ADC/DAC reference input.
- Initial accuracy
- ±0.1% (laser-trimmed precision) to ±2% (general purpose). For 16-bit ADCs, accuracy >±0.1% is wasted because resolution is finer.
- Temperature drift (ppm/°C)
- 5-25 ppm/°C for general use, <5 ppm/°C for instrumentation.
- Long-term drift
- Typically specified in ppm/√khr. Matters for instruments that must hold calibration for years.
- Noise (μV peak-to-peak in 0.1-10 Hz band)
- Critical for low-noise analog. Buried-Zener references are the quietest; bandgap references are noisier but run at lower voltage and current.
- Output current and topology
- Series (3-terminal) for driving loads. Shunt (2-terminal Zener-like) for low-current threshold applications, simpler.
What Magnias offers
Two adjustable shunt references in SOT23: TL431BL-B (2.495 V ±0.5%, adjustable up to 36 V) and TL432CL (1.24 V, 0.5% or 1%, adjustable up to 18 V). Use them for regulator feedback, threshold setting and general-purpose references.
Common questions
TL431. Is it really a voltage reference?
Yes, the most common one ever, it's a programmable shunt reference with internal bandgap, used as a regulator feedback element and a general-purpose 2.5 V reference.
Series or shunt reference?
Series (3-terminal) gives you a regulated output node that can drive other circuits, like a tiny LDO. Shunt (2-terminal) just sits across a current source like a Zener and clamps the voltage, lower current, simpler, but no drive capability.
Bandgap vs Zener-based reference?
Buried-Zener references have the lowest noise and the best long-term stability, but they need a supply of about 7 V or more and draw more current. Bandgap references work at low voltage and low current, and good modern bandgaps close much of the gap.