CHAPTER 27 ■ ENCORE
Voltage Regulator Packages
Like other parts, voltage regulators come in a variety of packages (see Figure 27-3). The most basic regulators
take positive power on one pin, negative power on another pin, and output a steady voltage on a third pin.
Fancier regulators have additional pins that indicate a low battery or provide a power-suspend feature.
Figure 27-3. Robot-friendly voltage regulators: (left to right) classic 7805, high-efficiency PTN78000 switching-
regulator, low-dropout MCP1826, and low-dropout MCP1702 in a compact package
Many regulated voltage values are available, such as 1.8 V, 2.8 V, 3.3 V, 5 V, 8 V, and 12 V. The most
common voltage for hobbyist projects is 5 volts, as many chips and sensors operate at that voltage. To save
power, lower voltages are more common with modern commercial products, such as smart phones and
other handheld devices. Some voltage regulators allow you to specify any voltage within a reasonable range
by attaching a pair of resistors.
Voltage Regulator Types
There are two major types of voltage regulators:
- Linear regulators require a battery voltage above the final desired voltage, with the
regulator discarding the extra. That’s a waste of power, but it works. So, a 9 V battery
could be regulated at 5 V for its entire useful life. The voltage regulator wouldn’t
output 4 V when the battery was at 8 V, it would always output 5 V. The discarded
extra voltage is turned into heat. - Switching regulators conserve power by converting voltage using capacitors or
inductors. Excess voltage is almost always converted into additional current. Some
switching regulators are designed to step-down higher voltages, some step-up
lower voltages, and others buck-or-boost (raise or lower) depending on the battery’s
output. Although not 100% efficient, the best switching regulators approach 90%
under ideal conditions. Besides saving power (thus extending battery life), switching
regulators don’t get as hot as linear regulators.