LDO is the meaning of low voltage drop, which has a description: Low voltage drop (LDO) linear regulator low cost, low noise, static current is small, these are its outstanding advantages.
It also requires very few external components, usually only one or two bypass capacitors.
The new LDO linear regulator achieves the following: output noise of 30μV, PSRR of 60dB, static current of 6μA, and voltage drop of only 100mV. Dc-dc means DC to DC (to) DC (conversion of different DC power supply values), as long as it meets this definition, it can be called DC-DC converter, including LDO. But the general saying is that the DC change (to) DC by the switching mode of the device is called DC-DC.
The main reason why the performance of the LDO linear regulator can reach this level is that the regulator is a P-channel MOSFET, while the ordinary linear regulator is a PNP transistor.
P-channel MOSFETs are voltage-driven and do not require current, so the current consumed by the device itself is greatly reduced. On the other hand, in a circuit using PNP transistors, in order to prevent the PNP transistor from entering a saturated state and reducing the output capacity, the voltage drop between the input and output can not be too low; The voltage drop on a p-channel MOSFET is roughly equal to the product of the output current and the on-resistance.
Because the on-resistance of the MOSFET is small, the voltage drop on it is very low.
If the input voltage and output voltage are very close, it is best to use the LDO regulator, which can achieve high efficiency.
If the input voltage and the output voltage are not very close, it is necessary to consider the switch type DC-DC, because it can be known from the above principle that the input current of the LDO is basically equal to the output current, if the voltage drop is too large, the energy consumption on the LDO is too large, the efficiency is not high. DC-DC converters include boost, buck, boost\/buck, and anti-equality circuits. The advantages of DC-DC converters are high efficiency, high output current and low static current.
With improved integration, many new DC-DC converters require only a few external inductors and filter capacitors.
However, the output pulsation and switching noise of this type of power controller are relatively high and the cost is relatively high. In short, the boost must be selected DC-DC, buck, whether to choose DCDC or LDO, to compare in cost, efficiency, noise and performance.
LDO (Low voltage Difference linear Regulator) and DC-DC (DC-DC converter) are two common power management devices, and their main difference is the way they regulate the input voltage to the desired output voltage. Here are the differences, pros and cons:
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difference
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Different working principles: LDO reduces the input voltage to the desired output voltage, and the output voltage is the sum of the pressure difference between the input voltage and its depressurization; The DC-DC converter adjusts the input voltage to the desired output voltage by switching the circuit.
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Different efficiency: Due to the way Ldos work, they are generally less efficient than DC-DC converters. LDO is especially inefficient when the input voltage is higher than the output voltage.
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Cost is different: DC-DC converters typically cost more compared to Ldos because they require more electronic components and more complex control circuits.
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merit and demerit
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Advantages of LDO:
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Easy to use, does not require too many external components;
The price is relatively low.
Disadvantages of LDO:
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Low efficiency, especially when the input voltage is higher than the output voltage;
Can withstand the load current is small;
High heat output.
Advantages of DC-DC converters:
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High efficiency, can achieve efficient conversion in different input and output voltage ranges;
Higher load capacity;
Small size, light weight.
Disadvantages of DC-DC converter:
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High complexity requires more components and control circuits;
The output voltage accuracy is lower than LDO;
The cost is relatively high.
In summary, the choice of LDO or DC-DC converter depends on the specific application needs. If the output voltage accuracy requirements are high, the current requirements are not large, and the cost requirements are low, LDO is more suitable; If you need higher efficiency, greater load capacity and smaller volume, choose a DC-DC converter is more suitable.
LDO: LOW DROPOUT VOLTAGE LDO (short for low dropout voltage regulator, rectifier), low voltage difference linear regulator, so the name is a linear regulator, can only be used in step-down applications, that is, the output voltage must be less than the input voltage.
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Advantages: Good stability, fast load response, small output ripple.
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Disadvantages: Low efficiency, input and output voltage difference can not be too large. The load should not be too large, the current maximum LDO is 5A (but there are many restrictions to ensure the output of 5A)
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DC\/DC: DC voltage to DC voltage. Strictly speaking, LDO is also a kind of DC\/DC, but at present DC\/DC refers to switching power supply, with many topologies, such as BUCK, BOOST and so on.
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Advantages: High efficiency, wide input voltage range.
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Disadvantages: The load response is worse than LDO, and the output ripple is larger than LDO.