What is an LDO?
Power management is an important design consideration for many products, especially for devices that rely on a battery for their power.
A voltage regulator is an electronic component that automatically provides a regulated and controlled output voltage to the various circuits inside an electronic device. The two main categories of voltage regulators are low dropout (LDO) linear voltage regulators and switching regulators. There is certainly a significant usage of switch-mode power supplies for the benefits they provide in power density and overall efficiency; however, LDOs are also used in a wide variety of applications today, and are an important component for you to understand and consider. For example, LDOs are used due to their low-noise output voltage, small size, low shutdown current, and low cost when compared to switching regulators. With so many possible LDO applications and a large number of parameters that can be optimized for each LDO, it’s not easy to determine which LDO is best suited for a particular application.
5 Basic DC Parameters
To begin selecting an LDO for your system, it’s important to understand the basic DC parameters required. The LDO you choose must operate within a range of required DC parameters to provide the required functionality for a particular application. Following are five typical, basic DC parameters for you to consider.
Input Voltage Range
The input voltage range determines the maximum and minimum allowable input supply for the LDO. Input supplies that are higher than the maximum allowable input can damage the LDO. The lowest input supply must be higher than the LDO output voltage plus the dropout voltage.
Output Voltage Range
The output voltage of an LDO may be fixed or programmable. If the output voltage is programmable, it is important to know the maximum and minimum limits of the output voltage programming range. The output voltage range specification provides this information. It is also useful to know the output voltage step size.
The dropout voltage is the differential voltage between the input and the output for which the regulator output no longer maintains regulation against further reductions in input voltage. Typically, the LDO dropout voltage is specified as the input voltage level that causes the output voltage to drop 100 mV below it’s programmed, regulated value. Since an LDO must provide the required constant voltage as the battery discharges, a small dropout voltage is very important as the smaller the dropout voltage, the greater the useful input voltage from the battery and therefore the longer the run time.
Maximum Output Current
This parameter is the maximum output current that the LDO can provide while still meeting the rest of the required parameters.
Output Voltage Accuracy
The output voltage accuracy describes the typical and worst-case deviation of the output voltage with respect to the nominal LDO output voltage. The overall output voltage accuracy also includes the effects of line regulation and load regulation.
Low dropout linear voltage regulators (LDOs) are a key component used in multiple applications. With this basic understanding of the typical DC parameters you should consider, you can move on to exploring the different AC parameters and features required of your LDO. For a comprehensive look at all of the DC, AC, and other optional parameters and features to consider, download our full LDO guide: