The input voltage to the LM317 must be at least 1.5v greater than the output voltage. LM317 calculator. This calculator will work for most DC Voltage Regulators with a reference voltage (VREF) of 1.25. Typically, the program resistor (R1) is 240 ohms for the LM117, LM317, LM138, and LM150. Some said Iadj is very low current. So, we may reduce.
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.
Feb 17, 2018 - To find more books about daftar persamaan ic download, you can use related keywords: Download Buku Persamaan Ic Dan Transistor. You can expect performance of both the line and load regulation using the LM317 / LM338 / LM350 adjustable voltage regulators over that of standard fixed voltage regulator. But this circuit can be created with a single IC is lm317 based variable power supply. The LM317 or LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to the 37V output range, And has many special features that I like are: Output Voltage Tolerance 1%; Line Regulation 0.01%. Komparator berfungsi sebagai pembanding antar tegangan output dan tegangan referensi, dimana besarnya tegangan output dapat dihitung dari persamaan Universitas Sumatera Utara dibawah. Circuit Protection adalah rangkaian pelindung IC LM317 dari erjadinya arus konrsleting dan sebagi pelindung IC dari panan kerlebihan. 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.
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]).
Persamaan Ic Regulator Lm317
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. |
Persamaan Ic Lm317t
- 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
Pin Configuration:
Pin Number | Pin Name | Description |
1 | Adjust | This pins adjusts the output voltage |
2 | Output Voltage (Vout) | The regulated output voltage set by the adjust pin can be obtained from this pin |
3 | Input Voltage (Vin) | The input voltage which has to be regulated is given to this pin |
Features:
- Adjustable 3-terminal positive voltage regulator
- Output voltage can be set to range from 1.25V to 37V
- Output current is 1.5A
- Maximum Input to output voltage difference is 40V, recommended 15V
- Maximum output current when voltage difference is 15V is 2.2A
- Operating junction temperature is 125°C
- Available in To-220, SOT223, TO263 Package
Note: Complete Technical Details can be found at the LM317 datasheet given at the end of this page.
Alternative Voltage Regulators:
LM7805, LM7806, LM7809, LM7812, LM7905, LM7912, LM117V33, XC6206P332MR.
LM317 Equivalents:
LT1086, LM1117 (SMD), PB137, LM337 (Negative Variable Voltage regulator)
Where to use LM317:
When it comes to variable voltage regulation requirements LM317 would most likely be the first choice. Apart from using it as a variable voltage regulator, it can also be used as a fixed voltage regulator, current limiter, Battery charger, AC voltage regulator and even as an adjustable current regulator. One notable drawback of this IC is that it has a voltage drop of about 2.5 across it during regulation, so if you looking to avoid that problem look into the other equivalent IC’s given above.
So, if you are looking for a variable voltage regulator to deliver current up to 1.5A then this regulator IC might be the right choice for your application.
How to use LM317:
LM317 is a 3-terminal regulator IC and it is very simple to use. It has many application circuits in its datasheet, but this IC is known for being used as a variable voltage regulator. So, let’s look into how to use this IC as a variable voltage regulator.
As said earlier the IC has 3 pins, in which the input voltage is supplied to pin3 (VIN) then using a pair of resistors (potential divider) we set a voltage at pin 1 (Adjust) which will decide the output voltage of the IC that is given out at pin 2 (VOUT). Now to make it act as a variable voltage regulator we have to set variable voltages at pin 1 which can be done by using a potentiometer in the potential divider. The below circuit is designed to take 12V (you can supply up to 24V) as input and regulate it from 1.25V to 10V.
The Resistor R1 (1K) and the potentiometer (10k) together creates a potential difference at adjust pin which regulates the output pin accordingly. The formulae to calculate the Output voltage based on the value of resistors is
VOUT = 1.25 × (1 + (R2/R1))
Now, let’s verify this formula for the above circuit. The value of R1 is 1000 ohms and the value of R2 (potentiometer) is 5000 because it is a 10k potentiometer placed at 50% (50/100 of 1000 is 5000).
Vout = 1.25 × (1 + (5000/1000))
= 1.25 × 6
= 7.5V
And the simulation shows 7.7 V which is pretty much close. You can vary the output voltage by simply varying the potentiometer. In our circuit, a motor is connected as a load which consumes around 650mA you can connect any load up to 1.5A.
The same formulae can also be used to calculate the value of resistor for you required output voltage. One easy way to do this is to use this online calculator to randomly substitute the value of resistors you have and check which output voltage you will get.
Applications:
- Used for Positive voltage regulations
- Variable power supply
- Current limiting circuits
- Reverse polarity circuits
- Commonly used in Desktop PC, DVD and other consumer products
- Used in motor control circuits