Typical circuit diagram and analysis __asm1117-3.3 of ASM1117-3.3V voltage regulator chip

Today, the circuit diagram of SD card module, found that the operating voltage of SD card is 3.3V, so need to use voltage regulator chip to convert 5V power supply to 3.3V voltage, so a little bit about the voltage regulator chip data

We choose the voltage regulator chip is asm1117-3.3, encapsulated as SOT-223

But in the drawing of the schematic diagram of the problem encountered, we found in the schematic diagram of two asm1117-3.3v chip schematic diagram, respectively:

The first one is four feet, the second is three feet, but look at the package, the two schematic diagram of the package are SOT-223, but the SOT-223 package is four feet, the problem that bothers me is why the three-legged schematic diagram can correspond to the four-foot package, and then read the chip manual to solve this puzzle. The original chip 2 feet and 4 feet are connected, so even the three-legged schematic diagram corresponding to the four-foot package is not related to

The next is the typical schematic diagram of asm1117-3.3v, because I chose the four-foot schematic, so here put four-legged schematic diagram of the typical circuit:

We also had a problem when we were drawing this circuit, The components of the inductor position between the network label VDD3.3 and the VCC3.3 have not been identified at first, because we look for a lot of asm1117-3.3 circuits, there are inductance, but also the use of resistors, and then after careful reading the chip manual and asked the relevant knowledge of the teacher, know that the position of the components can not connect, Will not have much effect on the circuit.

The following is an analysis of the circuit:

1, D1 function is to prevent power supply reverse connection.

2, C01, C02 is the power input filter.

3, VDD3.3 is 3.3V power supply, for digital circuit use,

4, L1, L2 is isolated filter inductance.

5, VCC3.3 is 3.3V power supply, for analog circuit use.

will be a voltage regulator chip into a separate module The advantage is that all the peripherals in need of the level of conversion can be directly through the network label to come in, and do not need to draw a circuit, so that both can save the time of drawing, but also can save the cost of components.

In addition to the 3.3V voltage regulator chip, this project also uses the 2.5V voltage regulator chip, the circuit is very similar to the method