Linear Regulator (LDO)

Linear Regulator (LDO)

When the output voltage is below the input voltage, a linear regulator (LDO) or Buck converter (buck) must be considered from the load supply and the voltage drop ratio

Low voltage drop-down linear regulators (LDOs) are suitable for applications where low noise, low current, and low voltage drop ratios are required.

The LDO regulates the output voltage by controlling the conduction of the passive component in a linear manner. The linear regulator provides an accurate, noise-free output voltage and fast response to load changes.

However, the linear voltage regulation method also represents the voltage difference between the input and output and its average load current will be converted to the power dissipation of the LDO passive component. The calculation of power dissipation is as follows:

PD = (vin-vout) xiload

It can be seen that high voltage drop ratios and high load currents produce higher power dissipation.

The higher the power dissipation generally requires the larger the LDO package size, which increases the overall cost, PCB area, and operating temperature of the application system. When LDO power dissipation is above 0.8W, it is wiser to switch to Buck Converter (buck).

When choosing an LDO, you must consider the input and output voltage ranges, the load capacity of the Ldo, and the power dissipation capability of the chip package. The Ldo's input/output voltage difference ratio needs to be higher than the rated minimum voltage difference (dropout Voltage), i.e. vin-vout > Droput Voltage, otherwise the Ldo will not function properly.

When using LDOs in micro-electric applications, such as those that must rely on a single battery for several years of power, the low quiescent current (IQ) Ldo must be chosen to avoid unnecessary waste of power.

Linear Regulator (LDO)