A Question About Reading and Calculating Thermal Resistance of a Voltage Regulator From Its Datashee

You have calculated the power dissipated in the wind gauge - what you need to know is the power dissipated in the LM317. The wind vane will draw 1 mA, and you have 3 volts across the LM317, for a power dissipation of 3 mW due to the load. However, the LM317 requires a minimum load current of 5 mA for proper operation - the voltage-setting resistors are usually selected to draw that current.

With 1 mA for the wind gauge, and 5 mA for the LM317 operation, the LM317 will dissipate about 6 mW - no need for any heat sink at such a low power. You could use a TO-92 packaged LM317 without concern

I have this voltage regulator from this supplier and the exact model name is given as: "LM317T/NOPB".

I plan to use this circuit to power a windwane's potentiometer which is around 10k:

As you see I want to set the excitation voltage for the vane pot to around 9 or 10V where the opamp will be supplied directly from a 12V switch mode power supply. For this purpose I will use an LM317 to obtain 9 or 10V for the vane excitation. So I will set LM317 for 9 or 10V DC. I will mount the vane in a box around 50m height which will stay there at least 3 months.

Since I will use a linear voltage regulator I decided to find out whether I need a heatsink.

I have encountered two challenges which I put here as questions:

1-) In the datasheet when I check the thermal resistances I cannot figure out which model I should use:

Mine is T0-220, but in the datasheet there is two types namely as KCT and KCS. But my model is "LM317T/NOPB". And on it it is written "LM317T P". So should I use the thermal resistance for KCT or KCS?

2-) Here is how I calculate the T:

T JA * P

In my case:

P V^2 / R 10^2 / 10000 0.01W

But for junction to ambient temperature I used to use the following:

Junction to ambient Junction to case Case to Ambient

But in the datasheet there is no Case to Ambient but there is Junction to ambient. Does "junction to ambient" already include "case to ambient"? Should I in my case only use Junction to ambient? If so in my case T becomes like 4C, and I conclude I don't need heatsink. Do I calculate correct and does it matter the duration like three months when it comes to using heatsink?

get in touch with us
Artículos recomendados
Reference Design of Power Supply and Serializer for Automobile Camera Module
A seemingly simple design, in fact, is full of the efforts and day and night of digital engineers. This design needs to be tempered and evaluated repeatedly before it can be put on the market. Ti designs reference design library, sincerely create a classic for you! Want to find more reference designs? Log in Ti designs reference design library and you will have the design you want!Ti designs design library will launch a series of selected reference designs for you, including industrial, medical, automotive electronics, factory automation and control, building automation, personal electronics and other applications. It will be updated every week. Don't miss it! Now, let's take a look at the good recommendations in the fifth issue of "automotive electronic reference design"!Design OverviewPmp9351 is a compact power supply and serializer solution for automotive auxiliary camera module, using omnivision image sensor ov10635. This reference board has two lmr22007 Synchronous Step-Down regulators, which provide two 3.3V outputs and one 1.5V output to power the ov10635 evaluation board bypassing the on-board LDO. This design occupies 20x20mm effective PCB board area. The system input voltage is 9V rated voltage from ECU, and its input range is 5.5V to 20V. This reference board includes a ds90ub913q serializer and supports a coaxial cable power supply configuration, allowing the transmission of input power and FPD link III signals through a coaxial cable.Design system block diagram (click here to download the complete block diagram)Design characteristics:·Power supply and serializer solution specially designed for omnivision ov10635 image sensor in automobile camera·Compact solution size, circuit board area 20x20mm·3.3V and 1.5V outputs, including output filters to cover I / O, core, analog voltage rail and ensure high image quality·5.5V to 20V working input voltage range, 9V rated input from ECU·The coaxial cable power supply configuration transmits the input power supply and FPD link III signal through a coaxial cable·Through a compatible interface, the ov10635 EVM can be connected with only a slight modification of the circuit boardDesign documents (click here to download the complete design resources)Design demonstration:Relevant design recommendations:Reference design 1: Automobile USB battery charging reference designDescription: the size of the USB battery charging reference design has been optimized and can be installed in the automobile power supply accessories port. The design adopts a USB special charging port controller with integrated current limiting power switch and 42V DC / DC converter. High integration and small package size create a small shape.Reference design 2: reference design of dual port automobile USB chargerDescription: by using tps40170 PWM step-down controller, this power management reference design provides 5V regulated output with its small shape specification to power two USB ports, of which each port is 2.1a (4.2a in total). After optimization, this design adopts 12V rated input and can accept 8-60v.For the original text, please refer to: http://www.deyisupport.com/blog/b/behindthewheel/archive/2014/08/04/51784.aspxTexas Instruments online technical support community answers technical problems and provides technical support for Chinese electronic engineers. Deyi community involves analog electronic technology, single chip microcomputer, MCU, embedded system, DSP and digital signal processing. It is the preferred technical exchange platform for electronic engineers designed with Ti chip. More Forum Highlights, please visit: http://www.deyisupport.com/
Composition, Advantages and Disadvantages of Modular UPS Power Supply
Use and Precautions of UPS Power Supply
How to Optimize Base Station System with Digital Power Supply
The New Form of Power Supply 3.3V and 5V Will Be Replaced by 12V
Maintenance and Management of UPS Power Supply System (teach You to Use Your UPS Power Supply Reason
Common Problems and Solutions of Switching Power Supply Commissioning
Can Servers Run, If Only 1 Power Supply Is Powered?
How Can the LED Driving Power Supply Pass the CE Certification? What Are the Requirements
Good UPS (Uninterruptible Power Supply)?
related searches
Common Problems and Solutions of Switching Power Supply Commissioning
Can Servers Run, If Only 1 Power Supply Is Powered?
Forcibly Underclocking at Night
5 Best Food Truck Generators in 2020 Reviews
In the 'security' Way of LED Street Lamp Power Supply
Ham Radio Power Supply Question?
How Big of a Power Supply Do I Need?
HP Pavilion Laptop's Lights Flashing on and Off
Share an Article on the Design and Experimental Research of High Voltage DC Switching Power Supply
Contact us
  • Cel : +86 158-2024-2923
  • Tel(Fax) : +86 020-29835956
  • E-mail : info@torylight.com
    Facebook : Torylight sandy
  • Twitter : @torylight sandy

  • Add : No.1, XinHe Industrial Park, Huadu
  • District, Guangzhou, CHINA
Whatsapp :
+86 158-2024-2923
Copyright © 2021 Guangzhou Tory Light Co., Ltd. | Sitemap