LMCT-5 Datasheet, LM 5V Low Dropout Voltage Regulator Datasheet, buy LMCT Pin 5 and 6 need to be tied together on PCB board (5) ESD rating is based on the human body model, pF discharged LMCT/NOPB .. in TI data books or data sheets is permissible only if reproduction is without alteration. Digi-Key Part Number, LMCT/NOPB-ND. Copy LMCT/NOPB- ND. Quantity Datasheets, LMN, C Datasheet. Design Resources.

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If I hook up another 9V in parallel to add more currentit suddenly datashet to around 7V which I would expect if it were in series, but it’s not. Can you let us know what is printed on the third line? Check your caps, it might be leaky.

I haven’t experienced it personally, but you could have an issue there that might result in overheating. Hello, All I have is a cap between the output and ground at 22uf.

LMCT Datasheet(PDF) – National Semiconductor (TI)

Another, does your LCD has backlights? I will try it with the additional cap. Another data sheet says 0.

If you look at the diagram on the first page you will see some asterisks next to the capacitors.

LM2940ct 5.0 gets HOT quick.

The burn your finger kind of hot. Hi John, What is the input voltage to the regulator — can you measure it? I have a 22uf cap between the output and ground as specified in the datasheet for stability. I use these all the time, quite handy, especially with batteries since it can take a hit with the polarity hooked up backwards I can confirm for you that Left is Vin Middle is GND Right is output ive never tried without cap’s but yes they are for smoothing, but I dont know what effect outside of that they have my little breadboard bug that i made is rock solid 4.


The power in Watts being dissipated within the regulator is the voltage drop across the regulator times the current passing through it. I picked up some 5V 1A voltage regulators at a shop in town. The circuit I’m building works fine with a 5V regulated supply one you plug into the wallbut I’d like to expand the design to work off of batteries as well.

The output capacitor is required to ‘maintain stability’ which probably means to keep it from oscillating, which in turn could cause the strange output readings you are getting. I like to put a led on the output for the minimum load, and to show, solidly, that power IS really on. 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.

LDO Voltage Regulator (5V 1A LM2940CT, drop 0.5V @0.5A)

The actual values of the caps matter, too. Mine is unfortunately putting out more than 5V, which defeats the purpose of having a regulator. Even linear regulators are switching devices, which generate some noise that must be filtered. The LM gets hot after a few min which isn’t nice.


Many of the regulators require dahasheet on the input and output to minimize oscillation.

I wonder if this will pose a problem. Further reading of the spec sheet yields The acceptable range of ESR plotted versus load current is shown in the graph below. I wonder if anyone knows if the capacitors have any effect beyond smoothing out ripple. Sign In or Register to comment.

Is ths just because of the load placed on it due to the lcd? Lm2940dt-5.0 would work alright. Text in the Subject and Body of the message will be ignored. Should I use some other voltage regulator? Thank you for all the input.

The only things being powered in the circuit is the stamp and the LCD. Quick Links Categories Recent Discussions. Now that I look at it again, it seems that the markings on the package don’t match up with the datasheet. There is another possibility The battery is a little over 9V. Comments 10 Comments sorted by Date Added Votes. You probably still need the capacitor. Osgeld Faraday Member Posts: Voltage regulator not working as expected.