LDO is a linear regulator. A linear regulator subtracts excess voltage from an applied input voltage using a transistor or FET operating in its linear region to generate a regulated output voltage. The so-called voltage drop refers to the minimum difference between the input voltage and the output voltage required by the regulator to maintain the output voltage within the range of1000 mv above and below its rated value. Positive output voltage
LDO (low dropout) regulators usually use power transistors (also known as transmission devices) as PNP. This transistor allows saturation, so the regulator can have a very low voltage drop, usually about 200mV. In contrast, the traditional linear regulator using NPN composite power transistor has a voltage drop of about 2 V.. Negative output LDO uses NPN as its transmission device, and its working mode is similar to PNP device of positive output LDO.
The latest development uses CMOS power transistors, which can provide the lowest voltage drop. For CMOS, the only voltage drop on the regulator is caused by the on-resistance of the load current of the power supply equipment. If the load is small, the voltage drop produced by this method is only tens of millivolts.
DCDC means DC to DC (conversion of different DC power supply values), and it can be called DCDC converter as long as it meets this definition.
Including LDO. However, in general, a device that converts DC into DC by switching modes is called DCDC.
LDO means low voltage drop, and there is a paragraph explaining that the low voltage drop (LDO) linear regulator has low cost, low noise and small static current.
These are its outstanding advantages. It also requires few external components, usually only one or two bypass capacitors. Linear voltage stability of new LDO
The output noise is 30μV, PSRR is 60dB, the static current is 6μ A (TPS7800 1 of Ti reaches Iq=0.5uA), and the voltage drop is only100MV (LDO produced by Ti is called 0. 1mV). Linear stability of LDO
The main reason why the performance of the regulator can reach this level is that the regulator uses P-channel MOSFET instead of ordinary wires.
The gender regulator uses PNP transistors. P-channel MOSFET is voltage-driven and does not need current, so the device itself is greatly reduced.
Current consumed; On the other hand, in a circuit using PNP transistors, in order to prevent the PNP transistors from entering a saturated state, the output capacitance is reduced.
The voltage drop between input and output should not be too low; While the voltage drop on P-channel MOSFET is approximately equal to the output current and on-resistance.
The product of. Because the on-resistance of MOSFET is very small, the voltage drop across it is very low.