Differences between LVS and DC-DC Devices

Differences between LVS and DC-DC Devices

Dcdc means DC to DC (to) DC (conversion of different DC power supply values), as long as it complies with this definition, it can be called dcdc converter, including ldos. However, the general saying is that the device that implements DC-to-DC switch is called dcdc.

The low-voltage drop-down means that the low-voltage drop-down Linear Voltage Regulator features low costs, low noise, and low static current. It requires few external components, usually only one or two bypass capacitors. The new LVS provides the following metrics: output noise: 30μv, PSRR: 60db, static current: 6μa, and voltage drop: Only 100mV. The main reason for the performance of the LVS Linear Voltage Regulator to reach this level is that the adjustment tube uses a p-channel MOSFET, while the common Linear voltage regulator uses a PNP transistor. The P-Channel MOS are voltage-driven and do not require current, which greatly reduces the current consumed by the device itself. On the other hand, in the PNP transistor circuit, in order to prevent the PNP transistor from entering saturation and reduce the output capacity, the voltage drop between the input and output cannot be too low; the voltage drop on the p-Channel MOS is roughly equal to the product of the output current and the on-resistance. Because the on-resistance of the MOS is very small, the voltage drop on them is very low.
If the input voltage is very close to the output voltage, it is best to use an LVS regulator to achieve high efficiency. Therefore, most of the applications that convert the lithium-ion battery voltage to the 3 V output voltage are using an LVS regulator. Although the last 10 percent of the battery energy is not used, the voltage regulator can still ensure that the battery is working for a long time, while the noise is low.

If the input voltage is not very close to the output voltage, we need to consider using the switched dcdc. We should know from the above principle that the input current of the regulator is basically equal to the output current, if the pressure drop is too large, it consumes too much energy and is inefficient.

The DC-DC Converter includes boost, step-down, boost/step-down, and inverse equal circuit. The advantage of DC-DC converter is high efficiency, can output large current, small static current. With the increase of integration, many new DC-DC Converters only need several external inductors and filter capacitors. However, the output pulsation and switch noise of these power supply controllers are high and the cost is relatively high.
Over the past few years, with the development of semiconductor technology, the cost of surface-mounted inductors, capacitors, and highly integrated power control chips has been decreasing and the volume has become smaller and smaller. As a result, a low on-resistance transistor can output a high power, so it does not need an External High-Power FET. For example, for 3 V input voltage, the nfet on the chip can be used to obtain the output of 5 V/2a. Second, for small and medium power applications, you can use low-cost and small-sized packages. In addition, if the switching frequency is increased to 1 MHz, it can also reduce costs and use smaller-sized inductors and capacitors. Some new devices also add many new features, such as soft start, throttling, PFM, or PWM options.

In general, dcdc must be selected for boost, and dcdc or LDC should be selected for Buck, which should be compared in terms of cost, efficiency, noise and performance.