Electronics > Beginners
LM317AHVT and Heatsink
JS:
No problem with dual pots, you might want to use a 500Ω instead, as it might give ypu better control over the range, but 1k should be fine as well.
JS
mike_mike:
Dear Forum,
I made a layout for a LM317 power supply, using the attached schematic.
I don't know if I correctly made the layout. Please have a look at the layout and tell me if it is good.
I want to know only if the layout is correct. The schematic that I draw in KiCAD is correct because I checked it. I also added a LED and a current limiting resistor (R4 and J3).
The refdes of the components does not correspond from the schematic to the layout.
I was a little bit confused by the copper pours, because I don't know if I correctly made the copper pours.
mike_mike:
I have a question regarding the attached schematic.
In the LM317AHVT's datasheet is noted that the minimum load current can vary between 3.5mA and 12mA. When calculating the value of R1, what value 3.5mA or 12mA should I use ?
The current value of R1 is 122ohms (not 120 ohms), and the minimum load current in this situation is 10.2mA. It is sufficient this value of current for stabilization or it should be higher ?
Zero999:
--- Quote from: mike_mike on October 18, 2018, 07:12:08 pm ---I have a question regarding the attached schematic.
In the LM317AHVT's datasheet is noted that the minimum load current can vary between 3.5mA and 12mA. When calculating the value of R1, what value 3.5mA or 12mA should I use ?
The current value of R1 is 122ohms (not 120 ohms), and the minimum load current in this situation is 10.2mA. It is sufficient this value of current for stabilization or it should be higher ?
--- End quote ---
Well spotted. There's a lot of variance between parts with the same number. With 10.2mA, there's the very tiny outside chance the voltage may rise slightly beyond the specification, when it's unloaded, especially at extreme operating conditions i.e. high voltages high/low temperatures.
How many of these are you going to build? 99.99% of parts will work fine with 10.2mA, especially if their operating conditions aren't being pushed to extremes.
mike_mike:
I already built 2 power supplies and I am planning to build the 3 rd one.
I also planning a mini series (10 pieces) with PCB's from China.
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