In the circuit design, the commonly used power supply device no less than two, DC / DC and LDO.

LDO

LDO is a low dropout linear regulator, or called low voltage drop device, indicating that it is generally used for the need for antihypertensive occasions, with low cost, low noise, static current and other advantages. It requires fewer external components, usually only one or two bypass capacitors.

LDO linear regulator performance has been able to achieve this level, the main reason is that the regulator is a P-channel MOSFET. The P-channel MOSFET is voltage-driven and does not require current, thus greatly reducing the current consumed by the device itself. In addition, the voltage drop across the P-channel MOSFET is approximately equal to the product of the output current and the on-resistance. Since the on-resistance of the MOSFET is small, the voltage drop above it is very low.

DC / DC

DC / DC means DC (to) DC (conversion of different DC power values), as long as the definition of this can be called DC / DC converters, including LDO. But the general argument is to DC (to) DC by the switch to achieve the device called DC / DC.

DC / DC includes step-up, step-down, up / down and reverse circuits. DC / DC converter has the advantage of high efficiency, can output high current, quiescent current is small. With the increase in integration, many new DC / DC converters require only a few external inductors and filter capacitors. However, this type of power controller output pulse and switch noise, the cost is relatively high.

How to choose

If the input voltage and output voltage are very close, it is best to use the LDO regulator, can achieve high efficiency, the most important is the low cost. There are peer cattle for the summary of the application of LDO applications：
1、Such as the need for high-demand power supply noise suppression and ripple suppression of the product；
2、Such as PCB board area is small, such as mobile phones and other handheld electronic products；
3、Such as circuit power is not allowed to use inductors, such as mobile phones and other products；
4、Such as power supply needs to have a transient calibration and output status self-test function；
5、Such as requiring low voltage drop regulator, low power consumption of their products；
6、Such as requiring low cost and low cost solutions。

If the input voltage and output voltage difference is large, or the voltage drop is large, it is necessary to consider the use of switching DC / DC, because the LDO input current is basically equal to the output current, if the pressure drop Amotech is too large, consumption in LDO On the energy is too large, the efficiency is not high, so DC / DC is appropriate. DC / DC Although the high efficiency, you can output high current, but at the same time the output interference is larger, the volume is relatively large, the cost is slightly higher.

Summary, the boost is necessary to choose DC / DC, and buck, is to choose DC / DC or LDO, to the cost, efficiency, noise and performance comparison to do the analysis.