Low-Noise Power Supply Design
In modern electronic designs, ensuring the integrity of signal integrity is critical and one of the key considerations is the noise caused by the power supply needs to be minimized. Low Drop Out (linear regulators) are often used to provide a clean, low-noise power rail for sensitive circuits, and their applications extend from low-power IoT devices to complex high-performance systems.
What are LDOs?
LDOs are a type of voltage regulator designed to provide a stable output voltage while consuming low power. Unlike traditional linear regulators, LDOs are more efficient and generate less heat. This characteristic makes LDOs an attractive choice for applications where thermal management is a top priority.
Noise in Electrical Systems
Noise in power supplies can compromise the performance of even the most sophisticated electronic systems. It can manifest as AC ripple, distributor electronics corrupting signals, altering data, and potentially causing system failures. High-quality power rails are essential for maintaining signal integrity and ensuring reliable system operation.
Characteristics of Good LDOs
When selecting an LDO for a low-noise power rail, several key characteristics should be considered:
Low Dropout Voltage: A low dropout voltage ensures that the regulator consumes minimal power and generates minimal heat.
High PSRR: Power supply rejection ratio (PSRR) measures the LDO's ability to reject switching noise from the input voltage. A high PSRR value indicates that the LDO can effectively reject noise and maintain a clean output.
Reduced Noise Generation: Noise density measures the amount of noise generated by the LDO. A low noise density value indicates that the LDO is noise-free.
Flexible Output Voltage Range: The ability to set a wide range of output voltages allows designers to tailor the power rail to specific application requirements.
High Output Current Capacity: A high output current capacity ensures that the LDO can supply power to power-hungry circuits without compromising performance.
Implementation Considerations
To ensure optimal performance from an LDO, several implementation considerations must be taken into account:
Bypassing: Proper bypassing of the input capacitor to the LDO is essential to maintain low noise levels.
Minimizing Inductance: To minimize inductance and radiation, keep the LDO's input and output wires as short as possible.
Effective Grounding Scheme: A proper grounding scheme is crucial to prevent ground loops.
By selecting an LDO with the right characteristics and implementing it correctly, designers can create robust, low-noise power rails that will support high-performance electronic systems.