Persamaan Ic Lm317

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%. 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.

1. Persamaan Ic Regulator Lm317
2. Persamaan Ic Lm317t

• 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 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37 V. It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%.

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

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

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

Introduction

The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37V. In addition, it has the advantages of wide voltage regulation range, good voltage stability performance, low noise and high ripple suppression ratio.

A Tutorial of LM317 Adjustable Voltage Regulator

Catalog

I Basic Circuit

Figure 1. LM317 basic circuit diagram

The basic circuit of LM317 is shown in Figure 1. C1 is the input capacitance. When the capacitance distance between the voltage regulator and the rectifier filter is less than 5 ~ 10cm, C1 is not necessary. The recommended value is 0.1 μF. C2 is the output capacitance, which can improve the transient response. The recommended value is 1 μF.

II Minimum Stable Operating Current

LM317 voltage regulator block has a minimum stable working current. Some data call it the minimum output current, and some data call it the minimum discharge current. The minimum stable operating current is generally 1.5mA. Due to the different manufacturers and models of the LM317 voltage regulator block, the minimum stable operating current is also different, but it is generally not greater than 5mA. When the output current of LM317 voltage regulator block is less than its minimum stable working current, LM317 voltage regulator block can not function. When the output current of LM317 voltage regulator block is greater than its minimum stable working current, LM317 voltage regulator block can output stable DC voltage. If you do not pay attention to the minimum stable working current when making voltage stabilized power supply with LM317 voltage regulator block (as shown in Figure 2), the following abnormal phenomena may occur in your regulated power supply: The load voltage and no-load voltage output are different.

Figure 2. LM317 regulated power supply diagram

III Soft-Start Circuit

Figure 3 is a soft-start circuit using LM317. At the moment of power-on, the voltage of CE1 cannot change suddenly. Q1 is biased by R1 and R2 to be saturated and conduction, so that RP1 is short-circuited, which is equivalent to the grounding of the adjustment terminal of LM317. The power output is 1.25V. As the charging time of C2 increases, the output voltage gradually rises. The function of D1 is to quickly release the charge on C2 after the power is turned off, ensuring a normal soft start for the next startup.

Figure 3. Soft-Start Circuit

IV Basic Protection Circuit

D2 is the input short-circuit protection diode. CE1 is the filter capacitor at the regulating end, which has the function of stabilizing output and soft starting circuit. D1 is the output short-circuit protection diode. When the output terminal is short-circuited, CE1 discharges through D1. If there is no D1, CE1 discharges through LM317, which is easy to damage LM317. C1 is the input filter capacitor and C2 is the output filter capacitor. In actual use, the input and output are best connected in parallel by large and small capacitors.

Figure 4. Basic protection circuit

V Charging Circuit

The constant current charging circuit is shown in Figure 5. The constant current I = I=1.25/R1

Figure 5. Circuit diagram of constant current charging

The current-limiting charging circuit is shown in Figure 6. The current-limiting value = 0.7/R3

Figure 6. Current limiting charging circuit diagram

VI Overcurrent Protection Circuit

RSC=0.7/ISC (ISC is over-current protection current)

Figure 7. Over current protection circuit diagram

VII Extending Current Circuit

When the maximum output current is 2A and the output current of LM317 is assumed to be 1A, Q1 is on. The value of R can be calculated according to the following formula: R=UBE/(2-1)=0.7Ω

Figure 8. Extending Current Circuit

VIII High Voltage Output Circuit

Persamaan Ic Regulator Lm317

If the VZ value of the regulator tube is less than the maximum voltage difference between input and output (40V), the output voltage can be increased. When the output is short circuited, VZ and U1 are easy to be damaged, which is the disadvantage of basic high voltage output circuit.

Figure 9. High voltage output circuit

IX Constant Current Circuit

Persamaan Ic Lm317t

Constant current IL=1.25/R1

Figure 10. Constant current circuit

X Programmable Circuit

Figure 11. Programmable Circuit

XI Adjustable Voltage Calibrator

Figure 12. Adjustable voltage calibrator

Component Datasheet

FAQ