Key Topics : Linear Voltage Regulators, Low Dropout Regulators, Commonly available Voltage Regulators
When talking about Voltage regulators and understanding them we can identify couple of types that are being used commonly.- Linear Voltage Regulators
- Low Dropout Regulators (LDOs)
We will separately talk about the architecture of them and how these two types of regulators work. Linear Voltage Regulators and Low Dropout Regulators are almost same in architecture except LDOs can regulate a voltage which is closer to output voltage. Linear Voltage Regulators and Low Dropout Regulators are the mostly used type of regulators in micro-controller circuits due to following reasons compared to Switch Mode Power Supplies(Buck Converters).
- Compactness and Convenience in use.
- Low Cost (Very low cost compared to Buck Converters)
- Since most of the micro-controller circuits are low power consuming lower efficiency of the linear regulators does not really matter.
- Linear Regulators are better in noise sensitive applications compared to switch mode power supplies.
7805 is one of the most commonly used voltage regulator in micro-controller circuits. Also we've seen that there are different types of components like LM1117, LM317 and LM2940 are being used for the same purpose. Today we'll discuss, how does those linear regulators work, how to use them in our circuits and what are the pros and cons.
Few commonly available Voltage Regulators
Below specs are for you to get a mere understanding and they may change depending on the manufacturer and the package.
78XX is the most commonly used linear regulator in microcontroller applications. lets have a look at some of the specifications of this component. (L78XX, LM78XX, TA78XX etc)
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| 7805 and 7815 from two different manufacturers |
Vin = 7.5 V to 33 V
I0 = 1 A (some models rate even up to 1.5 A)
Vo = 7805 (5 V), 7806 (6 V), 7807 (7 V), 7809 (9 V),7812 (12 V), 7815 (15 V), 7818 (18 V), 7820 (20 V), 7824 (24 V)
Protections available : Over-current, Thermal, Safe operating
range limiting current
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| Smaller version of 7805 (100mA) |
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| SMT version of 7805 (500mA) |
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| AMS1117 |
Typical Application of Voltage Regulators
LM7805
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| Typical use of LM7805 |
Normally we add two capacitors to LM7805 for the following reasons
- 0.33uF input supply capacitor for filtering noise from the input
- 0.1uF output supply decoupling capacitor for stabilizing the output
AMS1117
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| Typical Use of AMS1117 |
Different manufacturers suggest different types and values for those two capacitors. Also it is important to note that 22uF capacitor should be placed close to the output pin of the regulator.
