Portable applications put more requirements outside the basic conditions.  
 
When selecting a low -voltage and low -voltage regulator (LDO), the basic problems that need to be considered include the input voltage range, the expected output voltage, the load current range, and the power consumption capacity of their packaging. However, portable applications need to consider more issues. The ground current or static current (IGD or IQ), the power supply wave texture (PSRR), and the size of the package are usually the element of the best LDO selection for portable applications.  
 
Input, output and reduce voltage:  
 
Select the input voltage range to adapt to the LDO of the power supply. The following table lists the voltage range of popular battery chemicals used by portable equipment. When determining whether the LDO can provide the expected output voltage, it is necessary to consider its voltage drop. The input voltage must be greater than the sum of the expected output voltage and a specific voltage drop, that is, VIN\\u003e Vout VDropout. If VIN is reduced below the necessary voltage, we say that LDO has a "voltage drop\\  
 
Pay attention to the performance changes during pressure drops. The error amplifier of the driving bypass transistor is completely opened or out of the "cocked" (cocked), so no loop gain. This means that the line and load adjustment are poor. In addition, PSRR also decreases significantly during pressure falling.  
 
The LOD that can provide expected output voltage is used as a fixed option to save the cost and space of the external resistor division. The external resistor division is generally used to set the output voltage of the adjustable device. Using adjustable LDOs can set output to provide internal reference voltage, which is generally about 1.2V, just connect the output to the feedback pin. Please confirm whether it has this function with manufacturers.