Switching Voltage Regulators
IC switching voltage regulators are integrated circuits (ICs) that store energy in an inductor, transformer, or capacitor and then use this storage device to transfer energy from the input to the output in discrete packets over a low-resistance switch. Feedback circuitry regulates the energy transfer to maintain a constant voltage within the load limits of the circuit. There are several types of IC switching voltage regulators. Buck or step-down converters convert a higher DC input voltage to a lower DC output voltage of the same polarity. Boost or step-up converters convert a lower DC input voltage to a higher DC output voltage of the same polarity. Buck-boost converters can be used for either step-up or step-down conversions, and to reverse or invert voltage polarity. IC switching voltage regulators are more efficient than IC linear voltage regulators, but produce greater amounts of noise. The output voltage can be fixed, or adjusted to a value within a specified range.
Important specifications for IC switching voltage regulators include regulated output voltage, input voltage, output current, switching frequency, efficiency, duty cycle and operating temperature. Both the output regulated voltage (Volt) and the input voltage (VIN) are minimum and maximum amounts in continuous mode (DC). The output current (IOUT) is measured under specified conditions. Efficiency, the ratio of output power to input power, measures the ability of IC switching voltage regulators to convert input energy into output energy. For example, an efficiency of 100% means that all of the input energy is transferred to the output. The duty cycle is the ratio between the on and off time of the output transistor. The operating temperature is a full-required range.
IC switching voltage regulators are available with a variety of features. Some devices have more than one output or channel. Others have an internal circuit to control the amount of current produced, or an error flag for monitoring outputs that drop below a nominal value. Reverse voltage protection prevents damage in applications where users can accidentally reverse battery polarity. Thermal shutdown protection turns off IC switching regulators when the temperature exceeds a predefined limit. Shutdown (inhibit) pins are used to disable regulator outputs.