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What is the difference between level shifter, voltage regulator and dc-dc converter?

My understanding is:

  • level shifter is used to convert one voltage into another voltage
  • voltage regulator is used to produce constant output voltage from high voltage
  • dc-dc converter is used to convert dc level into different level

Is this correct?

If I want to convert 5V voltage supply to 2.5V, do I need to use regulator, level shifter or dc-dc converter?

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A level shifter is usually a part that converts digital signals from one logic standard to another. It might also be called a translator. For example, the MC14504B converts TTL logic signals to CMOS levels, and a MC10H607 converts PECL signals to TTL. A level shifter isn't meant to provide power, it can only source as much current as its target logic levels require.

The terms voltage regulator and dc-dc converter are somewhat overlapping. Classic linear regulators are almost always called regulators. Linear regulators can only be used to produce a lower voltage from a higher one. Switching supply circuits might be called regulators or dc-dc converters. (Purists might claim that the regulator is just one part of a dc-dc converter circuit. That is the regulator is what provides the feedback control, whereas the dc-dc converter is a complete circuit including external magnetics, switching transistors or diodes, etc.) Switching supply circuits include different types that are able to produce either lower or higher voltages from an input voltage.

To produce 2.5 V from 5 V, you can use either a linear regulator or a "buck" switching converter.

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  • \$\begingroup\$ Thanks for your explanation. If I want to convert 2.5V to 5V, that means I need to use boost converter? Can I use linear regulator in this case? \$\endgroup\$ – nee Oct 5 '12 at 2:13
  • \$\begingroup\$ @nee, just as I said "Linear regulators can only be used to produce a lower voltage from a higher one." If your current need is small, there are alternatives to boost converters. But if you need more than about 100 mA, yes, you need a boost converter. \$\endgroup\$ – The Photon Oct 5 '12 at 15:50
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A level shifter is used between digital circuits in order to convert "high" and "low" as used by one of the circuits into "high" and "low" as used by the other. That both circuits usually use 0V for "low" is incidental.

A voltage regulator is used to take a possibly unstable voltage source of higher voltage and produce a smooth output voltage.

A DC-DC converter is used to provide one voltage given another as input. They usually have a voltage regulator in the output section.

To convert a 5V power supply into a 2.5V power supply you could use either a DC-DC converter or a voltage regulator; a level shifter would not be appropriate for this application.

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  • \$\begingroup\$ Thanks for your explanation. Can I know why I cannot use level shifter in this case? \$\endgroup\$ – nee Oct 5 '12 at 2:14
  • \$\begingroup\$ You could, if your power draw was low enough. But it would still be inappropriate. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 5 '12 at 4:55
  • \$\begingroup\$ Except for power consumption, what factors need to be considered ? \$\endgroup\$ – nee Oct 5 '12 at 6:23
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    \$\begingroup\$ The fact that that's completely not what it's for. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 5 '12 at 9:55
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    \$\begingroup\$ @nee, a level shifter normally needs you to provide power supplies at both levels involved. So it doesn't let you produce 5 V if you don't already have 5 V. \$\endgroup\$ – The Photon Oct 5 '12 at 15:51
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There are two main uses of electrical current:

  1. To actually provide power to operate a circuit or device. Most electronic circuits are designed to run with DC with a specified voltage range. For example the 5V supply for an Arduino needs to be between 4.75 and 5.25V. If the available power is outside the required range it needs to be changed to the value the device requires. A voltage regulator can be used to change a DC voltage that is higher than the required voltage (for example 9V in the Arduino case) or is variable (for example 7-12V for an Arduino with regulator) to a stable voltage that the device needs. A constraint with a normal (linear regulator) is that it can only reduce voltage and it throws away the energy difference between the two voltages. If you need to power a device from a voltage lower than it requires you can use a DC-DC converter. It can also be much more efficient than a linear regulator if the input voltage is much higher than the require device voltage (e.g. 12V input to power a 5V Arduino).
  2. To provide transfer of information. In this case the amount of power is usually small and the object is to pass information rather than power to operate the device. For digital information there are a number of accepted standards, for example 5V TTL where a 0 is represented by a voltage of between 0 and 0.8V and a 1 is represented by a voltage between 2.4v and 5V. Another standard is 3.3V TTL in which the high voltage is between 2.4V and 3.3V. If you need to exchange information between the two standards you may use a level shifter to interface the two devices. Another common voltage level translator is between the levels used in Rs232 to TTL (either 5V or 3.3v). Level shifters need to work at the speed at which the information is transferred which may be extremely fast in some case, maybe 100's of Megahertz.
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The above are great answers. I'm adding this one (I'm not the author), because I found it extremely helpful as a supplement.

Voltage translation is required when microprocessors and peripheral devices operate at different voltage levels within a system. Voltage translators interface between these system components and solve the problem of I/O voltage level incompatibility while retaining signal integrity.

Voltage translators can be used in any application where an interface is needed between system components with different I/O levels.

Voltage regulation is the ability of a system to provide near constant voltage over a wide range of load conditions. Voltage regulator is an electrical circuit designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.

kak111 from http://www.edaboard.com/thread229917.html

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