Generally integrated circuits are available in different forms like logic gates, 555 timers, microprocessors, microcontrollers, op-amps, and voltage regulator ICs like LM338, LM358, LM337, LM741, LM324 IC, and LM339 IC. So a voltage regulator is an electronic circuit that supplies a stable voltage instead of changes within the input voltage (or) load. So it is a significant component in power supply circuits. This IC can be designed with discrete electronic components like transistors and operational amplifiers. This article elaborates on LM337 IC which includes pinout, features, specifications, and its applications.
What is LM337 IC?
The LM337 is a three-terminal, adjustable, and negative voltage regulator that supplies above 1.5 Amps current over −1.2 V to −37 V output voltage. So this voltage regulator is very simple to utilize because needs two external resistors only to set the output voltage. This voltage regulator IC uses thermal shutdown, internal current limiting, and secure area compensation which makes it blow−out proof.
The LM337 IC is used in a wide range of applications like local and on-card regulation. In addition, this IC can also be utilized to make a programmable o/p regulator (or) by simply connecting a fixed resistor in between the adjustment & output pins, thus this regulator IC can be utilized as a precision current regulator.
How LM337 IC Work?
The LM337 IC works as an adjustable and negative voltage regulator, that means when an input voltage is provided to this IC, then it provides a stable and negative output voltage that can be set exactly with two external resistors while providing thermal protection and current limiting to avoid damage when overload occurs. This IC changes the output voltage by regulating the conductivity of a pass transistor depending on the voltage variation between its reference voltage & the preferred output voltage.
The LM337 IC includes a reference voltage, error amplifier, and pass transistor. Internal reference voltage works as a comparison point mainly for the output voltage. Error amplifier monitors the difference continuously between the reference voltage & the sampled output voltage. The internal pass transistor constantly adjusts its conductivity to either raise or reduce the current supply to the output by maintaining the preferred output voltage.
This IC has different features like current limiting; short-circuit protection & thermal overload protection to ensure secure and consistent operation. So these protections protect from extreme heat, short-circuit events & current conditions by enhancing the reliability of regulators within various applications.
LM337 IC Pin Configuration:
LM337 IC pin configuration is shown below. This IC includes three pins which are discussed below.
LM337 IC Pin Configuration
- Pin-1 (Adjust): This is an adjust pin which adjusts the o/p voltage
- Pin-2 (Vin/Input Voltage): The input voltage or Vin pin that has to be adjusted is provided to this pin.
- Pin-3 (Vout/Output Voltage): The regulated output voltage which can be set through the adjust pin can be attained from this pin.
Features & Specifications:
The features and specifications of LM337 IC include the following.
- LM337 IC is an adjustable negative voltage regulator.
- This IC includes three terminals.
- It is available in SOT223, To-220 & TO263 Packages.
- Output voltage can be set to range from -1.25V to -37V
- Maximum o/p current is -1.5Amps.
- The maximum differential I/O voltage is 40 volts.
- Its recommended differential I/O voltage is 15V.
- Maximum o/p current whenever voltage variation is 15V is -2.2Amps.
- Output current is above 1.5 Amps.
- Adjustable output voltage ranges from −1.2 V and −37 V
- It has internal thermal overload protection.
- Internal short circuit current limiting is constant with temperature.
- Output transistor secure area compensation.
- These Devices are RoHS Compliant & Pb−Free.
- It avoids stocking several fixed voltages.
- Floating operations can be done mainly for high-voltage applications.
- Its guaranteed output current is 1.5 Amps
- 0.3%/V typical load regulation
- Its typical line regulation is 0.01%V.
- Ripple rejection is 77 dB
- Thermal regulation is excellent like 0.002%/V
- Temperature coefficient is 50 ppm/°C.
- Its operating junction temperature is around 125°C
Equivalent & Alternatives
Equivalent LM337 ICs are; PB137, LT137, LM317, etc. Alternative LM337 ICs are; LM7912, LM7909, ,IP337AHVG, IP137AHVGBSS2, IP137AHVG, IP137AIG883B, 7703406UA, IP337AT, IP137G-BSS2, IP137G-BSS2, etc.
How do you use LM337 IC Long Term in a Circuit?
To use the LM337 IC in a circuit for the long term, ensure that the current supply stays under 1.5Amps, the output voltage below 37V & input voltage under 40V. Good thermal management helps maintain secure operating temperatures which range from -40° to 125°C. Corrosion-free and stable connections and connecting capacitors at I/O can decrease noise & voltage fluctuations. Testing voltage regularly below different conditions assists in spotting issues early.
Adjustable Bipolar Voltage Regulator Circuit with LM337 IC
The power supply for op-amp circuits must provide positive & negative voltages. So a simple adjustable bipolar voltage regulator circuit is designed here to provide ± 1.2V to ±2oV regulated supply. Here both LM317 IC & LM337 ICs are used as positive & negative voltage regulators correspondingly.
The required components to make this circuit mainly include; ¼-watt, ± 5% carbon resistors like 120Ω, 0.5Watts, 2 KΩ LIN variable resistors, capacitors like 4700 µF/25V electrolytic capacitors, 0.1 µF ceramic capacitors, 10 µF/35V and 1 µF/35V electrolytic capacitors, LM317K, LM337K, 1N5421 rectifier diodes, 230V AC primary and 1.5A secondary transformer. Connect this circuit as per the diagram shown below.
Adjustable Bipolar Voltage Regulator Circuit with LM337 IC
Working
The adjustable bipolar voltage regulator circuit with LM337 IC is shown below. This circuit is designed with two positive & negative adjustable voltage regulator IC, a bridge rectifier, a step-down transformer, and some electronic passive components like capacitor, resistor, etc.
In the above circuit, the main power supply is stepped down to 22V-0-22V with a center-tap transformer. After that, this voltage can be rectified with a bridge rectifier designed with four rectifier diodes. So, the pulsating positive and negative DC voltage can be filtered with a C1 capacitor.
The LM337 IC includes an internal feedback regulation as well as current passing elements. This IC can also have a variety of protection circuits like current limit & thermal shutdown. So these ICs can form adjustable bipolar power supply separately.
For each regulator in the circuit, VR1 & VR2 variable resistors are regulated for every regulator to provide a regulated output around ±1.2V to ±20 V. So C5 & C6 capacitors are used to progress AC ripple voltage rejection. But if any short circuit arises across the output of the regulator, then the C5 capacitor adjusts the current within the terminal. So the adjustable bipolar voltage regulator output can be measured by the following formula.
V0 = 1.25 x V (1 + VR1/R1)
Advantages & Disadvantages
The advantages of LM337 IC include the following.
- LM337 IC has several features to ensure secure and reliable operation. So all these features protect from excessive heat, short-circuit & over-current events by enhancing the reliability of regulators in a variety of applications.
- This IC is very simple to use and needs two external resistors only to set the output voltage.
- This IC uses thermal shutdown to secure area compensation & internal current limiting to make it fundamentally blow−out proof.
- The LM337 is a versatile IC that delivers an outstanding load regulation.
- This is an adjustable negative voltage regulator IC which is significant for ensuring stable output voltage in various electronic applications.
The disadvantages of LM337 IC include the following.
- This IC can damage from more than the maximum ratings
- LM337 IC may not supply complete output current at higher I/O voltages.
- This IC’s o/p voltage can drift because of thermal regulation so it affects temperature gradients.
- When LM337 IC is used with external capacitors then protection diodes are required to prevent the capacitors to the IC from discharging.
- The output voltage of this IC can change because of temperature gradients across the chip which is known as thermal regulation error.
- The complete output current may not be obtainable at higher I/O voltages.
- When the i/p & o/p voltages of this IC are very different, then its efficiency will be poor thus, huge loss will occur.
Applications
The applications of LM337 IC include the following.
- The LM337 IC can be used within power supplies, battery chargers, LED drivers, automotive electronics, etc.
- This IC can be used to make adjustable voltage regulators, programmable output regulators, etc.
- This IC can be utilized as a voltage reference.
- It can be used to make a precision current regulator by connecting a fixed resistor between the adjustment & output pins.
- This IC is used in different applications that need negative voltage supplies like bipolar amplifiers.
- This flexible voltage regulator can be used either as a fixed regulator or an adjustable regulator based on the requirement.
- This IC functions very well in battery chargers & power supplies if the input voltage ranges from 2V to 3V higher than the preferred output.
- The LM337 IC can also be used in complex systems to understand how its parts communicate with the whole system to ensure smooth performance & integration.
Please refer to this link for the LM337 IC Datasheet.
Thus, this is an overview of LM337 IC, pinout, features, specifications, circuit, working, pros, cons, and its uses. The LM337 IC is an adjustable three-terminal negative voltage regulator and is capable of supplying above 1.5 A current over the −1.2 V to −37 V output voltage range. So this IC is simple to use and needs two external resistors only to set the output voltage. Here is a question for you, what is LM317 IC?