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The burn your finger kind of hot. Keep in mind the adapter you have may be putting out more than 9 volts, or may not have a very clean output, both of which will make the regulator get hot. Another data sheet says 0. Also, remember the more voltage you have to drop and the more current you want to pull, the hotter the device will run.
Here’s a snip from p. Should I use some other voltage regulator?
The LM gets hot after a few min which isn’t nice. Photos – easier uploading and sharing.
Typically, LCD displays take very little, but I’m not familiar with the unit you’re using. If you aren’t running very much current, and your Vin isn’t too high, a small clip-on heat sink can significantly reduce the regulator’s temperature.
LM2940ct 5.0 gets HOT quick.
The only things being powered in the circuit is the stamp and the LCD. Your use of Yahoo! Basic Stamp List Subject: What are the caps on the BS2P40 demo board?
Text in the Subject and Body of the message will be ignored. Another, does your LCD has backlights?
Do you know about how much output current you have? Thank you for all the input. Comments 10 Comments sorted by Date Added Votes. There is another possibility My input is 9V, I’m using the power supply that came with the P40 demo board. Sign In or Register to comment. Friday, December 05, Otherwise the output impedance is too high and it oscillates.
The power in Watts being dissipated within the regulator is the voltage drop across the regulator times the current passing through it.
I believe the data sheets show a 0. I haven’t experienced it personally, but you could have an issue there that might result in overheating.
LDO Voltage Regulator (5V 1A LM2940CT, drop 0.5V @0.5A)
Hello, All I have is a cap between the output and ground at 22uf. Does it have a backlight? I will try it with the additional cap. It is essential that the output capacitor meet these requirements, or oscillations can result. Quick Links Categories Recent Discussions.
LMCT/NOPB from Texas Instruments
Many of the regulators require capacitance on the input and output to minimize oscillation. Check your caps, it might be leaky.
Is ths just because of the load placed on it due to the lcd? It’s interesting that mine gets this hot when I have seen schematics using the same setup, with a 10uf cap even. Groups is subject to http: I have a 22uf cap between the output and ground as specified in the datasheet for stability. I can’t find a schematic of it. The acceptable range of ESR plotted versus load current is shown in the graph below.
Hi John, What is the input voltage to the regulator — can you measure it?
Thanks, John In basicstamps yahoogroups. Did you take steps to obtain caps with appropriate ESR? Furthermore, hidden in the ap note the ones that I have seen is an admonition to have a minimum current load. I like to put a lm2940xt on the output for the minimum load, and to show, solidly, that power IS really on. The ESR of the output capacitor will cause loop instability if it is too high or too low.
Larger values of output capacitance will give improved transient response. That would km2940ct alright.