Power Transistor IC LM317LZ: Symbol, Features and Package
22 September 2023
Ⅱ. Symbol and Footprint of LM317LZ
Ⅴ. Pins and package of LM317LZ
Ⅵ. Advantages and disadvantages of LM317LZ
Ⅶ. How to optimize the efficiency of LM317LZ linear regulator?
The LM317LZ is a monolithic integrated circuit in a TO-92 package that can be used as a positive adjustable voltage regulator. It is designed to handle load currents up to 100 mAh and the output voltage is adjustable from 1.2 to 37 volts. Selecting the nominal output voltage using only a resistor divider makes the device easy to use while also reducing the inventory required for traditional fixed regulators.
The LM317LZ weighs only 179 mg, making it lightweight and portable. The device has a power supply rejection ratio (PSRR) of up to 80dB at 120Hz, effectively suppressing power supply noise and ensuring stable output voltage. The output voltage of LM317LZ has high accuracy and a tolerance of only 4%, making the output voltage more stable and reliable. In addition, LM317LZ also complies with the RoHS3 directive, which means that it complies with strict environmental regulations and has good environmental performance.
Replacement and equivalent：
• LM317LZX
• LM317LZG
• LM317LZ/NOPB
• Internal thermal overload protection
• Output transistor safe area compensation
• lnternal short circuit current limiting
• Output current in excess of 100 mA
• Output adjustable between 1.2 V and 37 V
• Floating operation for high-voltage applications
• Wide output voltage range: can be adjusted from 1.2 volts to 37 volts
• High linearity: the voltage difference between input and output is proportional to the output current, with high linearity
1. Pins
The pins of LM317LZ are as shown below:
Input Voltage (Vin): The LM317LZ can accept an unregulated input voltage, which is typically higher than the desired output voltage. The input voltage can vary, but must be within the range specified by the chip. The LM317LZ can handle a wide range of input voltages, making it suitable for a variety of applications.
Adjustable Output Voltage (Vout): The output voltage (Vout) can be adjusted by connecting external resistors (R1 and R2) between the ADJ pin, OUT pin and ground (GND). The calculation formula of Vout is: Vout=Vref×(R2+R1)
Adjustable Voltage Divider: The LM317LZ has two external resistors, R1 and R2, connected to the ADJ (Adjustment) and OUT pins. These resistors form a voltage divider network that allows us to set the desired output voltage.
2. Package
LM317LZ is a three-terminal voltage regulator in a TO-92-3 package. Its built-in heat sink can effectively dissipate the heat generated during operation, thereby ensuring the safety and stability of the circuit.
1. Advantages
(1) Versatility: It is suitable for a variety of applications, from powering LEDs to charging batteries.
(2) Stability: It can maintain a constant output voltage even if the input voltage fluctuates.
(3) Compact design: The compact appearance is suitable for projects with limited space.
(4) Customizability: The desired output voltage can be set with simple resistor selection.
2. Disadvantages
(1) The output voltage ripple is large and needs to be further reduced with a low dropout regulator.
(2) Due to its low efficiency, the use of electrical energy is not efficient. When powering a large current load with a large input/output voltage difference, it may dissipate a large amount of heat during operation, so it is necessary to install a heat sink such as a heat sink.
1. Improve heat dissipation conditions
We can place the LM317LZ in a location with better air circulation or install a heat sink to reduce the temperature and improve efficiency.
2. Choose the appropriate load resistor
The efficiency of LM317LZ will also be affected by the load current. The higher the load current, the lower the efficiency. Therefore, choosing a suitable load resistor can reduce the load current and thus improve efficiency.
3. Choose the appropriate input voltage
The efficiency of LM317LZ will be affected by the input voltage. Generally speaking, the higher the input voltage, the higher the efficiency.
4. Choose high-quality filter capacitors and temperature compensation capacitors
The quality of filter capacitors and temperature compensation capacitors has an important impact on the efficiency of LM317LZ.
5. Add a thermistor
Adding a thermistor to the circuit can monitor the heating of the LM317LZ. Once it detects that the temperature is too high, it can automatically reduce the output voltage to prevent overheating damage.
• Audio amplifier
• Battery charger: adjust charging voltage
• LED driver: for constant current LED lighting
• Power circuit: used to regulate voltage
Frequently Asked Questions
1. What is the operating temperature range of LM317LZ?
The operating temperature of LM317LZ ranges from 0°C to 125 °C.
2. How does the LM317LZ work?
The LM317LZ operates as a linear voltage regulator. It compares the output voltage to a reference voltage and adjusts the output to maintain a constant voltage difference between the reference and output voltages.
3. What is the typical input voltage range for the LM317LZ?
The LM317LZ typically operates with an input voltage range of 4.2V to 40V, depending on the specific model and manufacturer.
4. What are some common applications of the LM317LZ?
The LM317LZ is used in a wide range of applications, including powering electronic circuits, voltage regulation in power supplies, battery charging, and LED driver circuits.
5. What is the LM317LZ voltage regulator used for?
The LM317LZ is used to regulate and control the output voltage in electronic circuits. It can provide a stable, adjustable voltage output from a higher voltage source.
