The LM317 is a popular adjustable positive linear voltage regulator. It was designed by Bob Dobkin in 1976 while he worked at National Semiconductor.
The LM337 is the negative complement to the LM317, which regulates voltages below a reference. It was designed by Bob Pease, who also worked for National Semiconductor.
Lm317 3-terminal adjustable regulator slvs044o – september 1997 – revised july 2003 6 post office box 655303. dallas, texas 75265 application information c1 0.1 µf c2 1 µf r1 240 Ω input output adjust lm317 vi input output adjust vo lm317 r2 720 Ω r3 120 Ω r4 1 kΩ output adjust figure 5. Tracking preregulator circuit r1 1.2 kΩ r2. (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC package thermal metrics application report. 7.4 Thermal Information THERMAL METRIC(1) LM317 UNIT DCY (SOT-223) KCS (TO-220) KCT (TO-220) KTT (TO-263) 4 PINS 3 PINS 3 PINS 3 PINS Rθ(JA) Junction-to-ambient thermal resistance 66.8 23.5 37.9 38.0 °C/W.
Komparator berfungsi sebagai pembanding antar tegangan output dan tegangan referensi, dimana besarnya tegangan output dapat dihitung dari persamaan dibawah. Circuit Protection adalah rangkaian pelindung IC LM317 dari erjadinya arus konrsleting dan sebagi pelindung IC dari panan kerlebihan. LM317 with heat sink. The LM317 is a popular adjustable positive linear voltage regulator. It was designed by Bob Dobkin in 1976 while he worked at National Semiconductor. The LM337 is the negative complement to the LM317, which regulates voltages below a reference. It was designed by Bob Pease, who also worked for National Semiconductor.
Specifications[edit]
| Symbol | Parameter | Value | Unit |
|---|---|---|---|
| Vout | Output voltage range | 1.25 – 37 | V |
| Vin – Vout | Voltage differential | 3 – 40 | V |
| TJ | Operating junction temperature range | 0 – 125 | °C [1] |
| IO(MAX) | Maximum output current | 1.5 | A |
| IL(MIN) | Minimum load current | 3.5 mA typical, 12 mA maximum | [1] |
| PD | Power dissipation | Internally Limited | W [1] |
| RθJA | Thermal resistance, Junction to ambient | 80 | °C/W [1] |
| RθJC | Thermal resistance, Junction to case | 5 | °C/W [1] |
Without a heat sink with an ambient temperature at 50 °C such as on a hot summer day inside a box, a maximum power dissipation of (TJ-TA)/RθJA = ((125-50)/80) = 0.98 W can be permitted. (A piece of shiny sheet metal of aluminium with the dimensions 6 x 6 cm and 1.5 mm thick, results in a thermal resistance that permits 4.7 W of heat dissipation[2][3]).
In a constant voltage mode with an input voltage source at VIN at 34 V and a desired output voltage of 5 V, the maximum output current will be PMAX / (VI-VO) = 0.98 / (34-5) = 32 mA.
For a constant current mode with an input voltage source at VIN at 12 V and a forward voltage drop of VF=3.6 V, the maximum output current will be PMAX / (VI - VF) = 0.98 / (12-3.6) = 117 mA.
Operation[edit]
As linear regulators, the LM317 and LM337 are used in DC to DC converter applications.
Linear regulators inherently waste power; the power dissipated is the current passed multiplied by the voltage difference between input and output. A LM317 commonly requires a heat sink to prevent the operating temperature from rising too high. For large voltage differences, the power lost as heat can ultimately be greater than that provided to the circuit. This is the tradeoff for using linear regulators, which are a simple way to provide a stable voltage with few additional components. The alternative is to use a switching voltage regulator, which is usually more efficient, but has a larger footprint and requires a larger number of associated components.
In packages with a heat-dissipating mounting tab, such as TO-220, the tab is connected internally to the output pin which may make it necessary to electrically isolate the tab or the heat sink from other parts of the application circuit. Failure to do this may cause the circuit to short.
Voltage regulator[edit]
The LM317 has three pins: INput, OUTput, and ADJustment. Internally the device has a bandgap voltage reference which produces a stable reference voltage of Vref= 1.25 V followed by a feedback-stabilized amplifier with a relatively high output current capacity. How the adjustment pin is connected determines the output voltage as follows.
If the adjustment pin is connected to ground the output pin delivers a regulated voltage of 1.25 V at currents up to the maximum. Higher regulated voltages are obtained by connecting the adjustment pin to a resistive voltage divider between the output and ground. Then
Vout = Vref (1 + RL/RH)
Vref is the difference in voltage between the OUT pin and the ADJ pin.[4] Vref is typically 1.25 V during normal operation.
Because some quiescent current flows from the adjustment pin of the device, an error term is added:
- Vout = Vref (1 + RL/RH) + IQRL
To make the output more stable, the device is designed to keep the quiescent current at or below 100µA, making it possible to ignore the error term in nearly all practical cases.[5]
Current regulator[edit]
The device can be configured to regulate the current to a load, rather than the voltage, by replacing the low-side resistor of the divider with the load itself. The output current is that resulting from dropping the reference voltage across the resistor. Ideally, this is:
- Iout = Vref/RH
Accounting for quiescent current, this becomes:
- Iout = (Vref/RH) + IQ
LM317 can also be used to design various other circuits like 0 V to 30 V regulator circuit, adjustable regulator circuit with improved ripple rejection, precision current limiter circuit, tracking pre-regulator circuit, 1.25 V to 20 V regulator circuit with minimum program current, adjustable multiple on-card regulators with single control, battery charger circuit, 50 mA constant current battery charger circuit, slow turn-on 15 V regulator circuit, ac voltage regulator circuit, current-limited 6 V charger circuit, adjustable 4 V regulator circuit, high-current adjustable regulator circuit and many more.[4]
Compared to 78xx/79xx[edit]
The LM317 is an adjustable analogue to the popular 78xx fixed regulators. Like the LM317, each of the 78xx regulators is designed to adjust the output voltage until it is some fixed voltage above the adjustment pin (which in this case is labelled 'ground').
The mechanism used is similar enough that a voltage divider can be used in the same way as with the LM317 and the output follows the same formula, using the regulator's fixed voltage for Vref (e.g. 5 V for 7805). However, the 78xx device's quiescent current is substantially higher and less stable. Because of this, the error term in the formula cannot be ignored and the value of the low-side resistor becomes more critical.[6] More stable adjustments can be made by providing a reference voltage that is less sensitive than a resistive divider to current fluctuations, such as a diode drop or a voltage buffer. The LM317 is designed to compensate for these fluctuations internally, making such measures unnecessary.
The LM337 relates in the same way to the fixed 79xx regulators.
Second sources from Eastern Bloc[edit]
The LM317 has an East European equivalent, the B3170V, which was manufactured in the German Democratic Republic (East Germany) by HFO (part of Kombinat Mikroelektronik Erfurt).Also, in USSR was manufactured and most popular ICs K142EN12A and KR142EN12A. These ICs are functional analogues of the LM317
See also[edit]
References[edit]
- ^ abcde'KA317/LM317 3-Terminal Positive Adjustable Regulator'(PDF). Archived from the original on 17 December 2013. Retrieved 2013-12-17.CS1 maint: bot: original URL status unknown (link)
- ^'Calculating heat sinks'. November 2013. Retrieved 2016-04-16.
- ^Nuova Elettronica. Accidenti come scotta questo transistor. 1978, volume 11, pages 58-102
- ^ ab'LM317 3-Terminal Adjustable Regulator'(PDF). Texas Instruments. October 2014. pp. 11–16. Archived from the original(PDF) on 31 March 2015. Retrieved 31 March 2015.
- ^'LM117/LM317A/LM317-N 3-Terminal Adjustable Regulator'(PDF). August 2013. Retrieved 2017-08-28.
- ^'LM340-N/LM78XX Series 3-Terminal Positive Regulators'(PDF). March 2013. Archived from the original(PDF) on 18 April 2016. Retrieved 2017-08-28.
External links[edit]
| Wikimedia Commons has media related to LM317 and Voltage regulator circuits. |
- Band-Gap
- The Design of Band-Gap Reference Circuits: Trials and Tribulations – Robert Pease, National Semiconductor (shows LM317 design in Figure 4: LM117)
- LM317 Bandgap Voltage Reference Example (ECE 327) – Brief explanation of the temperature-independent bandgap reference circuit within the LM317.
- Datasheets / Databooks
- Voltage Regulator Databook (Historical 1980), National Semiconductor
- LM317 (positive), LM350 (3 Amp), Texas Instruments (TI acquired National Semiconductor)
- LM317 (positive), LM350 (3 Amp), ON Semiconductor
- LM317 (positive), STMicroelectronics
- LM337 (negative), Texas Instruments
LM317 is a very famous adjustable voltage regulator IC available in many different packages. Today we are going to discuss about LM317 pinout, equivalent, uses, features and other details about this IC.
LM317 IC Features / Technical Specifications
- Capable of providing upto 1.5A current at the output.
- Voltage adjustable from 1.2V to 37V
- Requires low external components
- Requires only two external resistors for output adjustment.
- Capable of short circuit protection
- Over heat shutdown function
- Low price
- Reliable to use in commercial applications
- Maximum input voltage is 40V DC
- Low standby current
LM317 Explained / Description
Persamaan Ic Regulator Lm317
Previously we have discussed some fixed voltage regulator ICs like LM7805, LM7806, LM7809, LM7812 and LM7815. All these ICs are designed to provide a fixed output voltage. But if there is requirement of adjustable output voltage then LM317 might be a good choice. LM317 is a widely used adjustable positive voltage regulator IC available in many different packages. The IC is widely used in commercial equipment and also by electronic students and learners. It is also one of a famous IC among electronic hobbyists and tinkerers. The main reason for its wide usage is because it contains entire adjustable regulated power supply circuitry in a single chip due to which one can easily make a low cost and reliable adjustable power supply of 1.2V to 37V DC output voltage with upto 1.5A output current capability and very low external components. Moreover the IC also contains many other features like short circuit protection, safe area and over heat protection which also makes it full proof and long term performer. Two external resistors can be used to adjust the output voltage of the IC. For getting a stable output the input voltage must be 2 to 3 volt higher than the output.
Additionally the LM317 IC is not limited to use for power supply circuits but it can also be used in many other applications.
Application Circuit
The application circuit shown in the above “LM317 IC pinout” image can be used to make LM317 power supply. The maximum input voltage can be applied to the circuit is 40V DC with 2 to 3 ampere. The output is adjustable from 1.2V to 37V DC with max output current of 1.5A. The output voltage can be adjusted with the help of 5K variable resistor. The 40V input is not mandatory you can provide any voltage between 3V to 40V DC, depends on your output voltage requirements. For example if you want to build a 1.2V to 12V adjustable power supply then provide 3V higher than your maximum output voltage. In the above requirement of 1.2V to 12V supply the input voltage must not less than 15V.
Applications
Voltage step down circuits
Lab power supplies
Battery Chargers
Persamaan Ic Lm317t
Solar Power Supplies
Microcontroller Related Applications
DC to DC converters
Portable Instruments
Replacement and Equivalent / Other Part Numbers
LM117, LM217, LM1086-ADJ, LT1086-ADJ, LT1117-ADJ, B29150, LM338, LM1084-ADJ. Some ICs may have different pin configuration from LM317, therefore check pin configuration before using in a circuit.
How to Safely Long Run in a Circuit
To get stable and long term performance from LM317 do not provide input voltage more than 40V DC, do not drive load of more than 1.5A, always use a proper heatsink with the IC and always operate in temperature above -55 centigrade and below +150 centigrade. The storage temperature is from -65 centigrade to +150 centigrade.
Datasheet
To Download the datasheet just copy and paste the below link in your browser.
https://cdn.datasheetspdf.com/pdf-down/L/M/3/LM317_ONSemiconductor.pdf