A Low-Dropout Regulator (LDO) is a type of voltage regulator that provides a stable output voltage even when the input voltage is only slightly higher than the desired output voltage. The term “low-dropout” refers to the minimal difference, or “dropout voltage,” between the input and output voltages required for the regulator to function properly.
Key Features of LDOs:
- Low Dropout Voltage: This is the key feature, allowing efficient operation when the input voltage is close to the output voltage.
- Low Noise: LDOs typically produce less noise compared to other types of regulators, making them suitable for sensitive analog circuits.
- Simpler Design: Unlike switching regulators, LDOs don’t require external inductors or switching components, which simplifies circuit design.
I used an LDO (Low-Dropout) regulator in a project where low noise and stable voltage were critical requirements. The application demanded precise regulation at either 3.6V or 12V, and the LDO was chosen for its ability to provide a clean, stable output with minimal voltage fluctuation, ensuring reliable operation in a noise-sensitive environment.
Because the application requires 12V or 3.6V, the only change needed in the circuit is the LDO.
Im using the LT1085CT-3.6#PBF and LT1085CT-12#PBF of Analog Devices (Datasheet).
Scheme:
Circuit Components:
- CR1 – 1N5819 (Schottky Diode): Used as a protection diode. It safeguards the circuit in case the power supply is connected with reverse polarity.
- RF1 REF030 (PTC): Positive Temperature Coefficient thermistor or resettable fuse component used for overcurrent protection in electronic circuits. PTC devices increase their resistance significantly when their temperature rises due to excessive current, limiting the current flow and protecting the circuit.
- C1 (Input Capacitor – Electrolytic): Essential when the regulator is positioned far from the power supply filter. This capacitor stabilizes the input voltage by reducing fluctuations and noise in the power supply.
- C2 (Bypass Capacitor – Ceramic): A small ceramic capacitor, typically 0.1uF, placed in parallel with C1 on the input side. It filters out noise and high-frequency distortions, ensuring a cleaner DC supply.
- LDO: LT1085CT-3.6#PBF/LT1085CT-12#PBF low-dropout (LDO) linear voltage regulator.
- C3/C4 (Output Capacitors): These capacitors help maintain a clean, stable output voltage for the connected circuit.
- J1/J2 (Terminal Blocks): Used for connecting wires to the circuit.
- Heatsink: I added a heatsink to dissipate the heat from the component.
Footprint:
3D model:
