Mystery IC, need help identifying

[tyguy2]

So I recently purchased a cheap Chinese Arduino Mega (it was only $9, so I wasn't expecting much), and with 3 weeks of troubleshooting my project, I accidentally shorted out what I presumed was a regulator and released the magic smoke. Does anyone know what type of regulator this is?

[singapol]

I don't know about this chinese clone but I think the regulator should be same or equivalent.
On the official arduino mega 2560 R3 schematic it is listed as NCP1117ST50T3G .Check the datasheet
for the voltage output. It could be 3V or 3.3V.

[tyguy2]

Thanks, I'll give that a try tomorrow. 

[wraper]

I don't know about this chinese clone but I think the regulator should be same or equivalent.
On the official arduino mega 2560 R3 schematic it is listed as NCP1117ST50T3G .Check the datasheet
for the voltage output. It could be 3V or 3.3V.

NCP1117ST50T3G is 5V

[tyguy2]

The voltage on the input pin is 5v, so I'm assuming it's a 3.3v regulator.

[wraper]

The voltage on the input pin is 5v, so I'm assuming it's a 3.3v regulator.

Then it is not NCP1117ST50T3G
EDIT: I think it's 5V LDO because it should be for power input jack, but you get the pinout wrong.

[Deathwish]

copies seem yo use a 800mA LDO

http://www.elecfreaks.com/wiki/index.php?title=Freaduino_Mega2560

[tyguy2]

So I could still use the board if I didn't install the LDO (or just an LM805)? I'm using this mega with a RAMPS 1.4, so I'm not even sure if that part is needed, considering the board is powered via a 12 - 24 volt power supply.

[singapol]

So I could still use the board if I didn't install the LDO (or just an LM805)? I'm using this mega with a RAMPS 1.4, so I'm not even sure if that part is needed, considering the board is powered via a 12 - 24 volt power supply.

Please do yourself a favour and learn to help yourself. Do not blindly take advice but verify it for yourself.
The regulator NCP1117ST50T3G is a fixed 5V output although usb has 5V supply , using 5V LDO ( low dropout regulator) will work even when input is down to 3.5V.It would filter out noisy 5V usb input.  Auduino mega2560 mcu need 5V supply to run so it's a MUST. You need to replace with a good unit ( they come in 2 types of pakages so check again). 12 - 24V power supply is for the stepper motors only. BTW LM78XX will not work because it will need a 3V headroom to give 5V output so input is at least 8V and above. You could bypass the regulator and use usb only but I can't gaurantee performance or stability of arduino.

http://www.onsemi.com/pub_link/Collateral/NCP1117-D.PDF

[promacjoe]

If you cannot find the proper regulator or just don't want to bother, remove the regulator and apply a regulated 5V directly to the 5V power pin.

Note: On the Official Arduino schematic, the 3V3 has 5 pins. the 5V regulator has 4 pins/Solder connection points.

Also note, never use an unregulated power supply on a Arduino. And never apply more than 12V to the power input port. Even though the specs say it can handle a higher voltage, It is not a good practice to run any regulator at it's upper limits. The regulator can heat up, and caused damage to your board.

[singapol]

So I could still use the board if I didn't install the LDO (or just an LM805)? I'm using this mega with a RAMPS 1.4, so I'm not even sure if that part is needed, considering the board is powered via a 12 - 24 volt power supply.

Please do yourself a favour and learn to help yourself. Do not blindly take advice but verify it for yourself.
The regulator NCP1117ST50T3G is a fixed 5V output although usb has 5V supply , using 5V LDO ( low dropout regulator) will work even when input is down to 3.5V.It would filter out noisy 5V usb input.  Auduino mega2560 mcu need 5V supply to run so it's a MUST. You need to replace with a good unit ( they come in 2 types of pakages so check again). 12 - 24V power supply is for the stepper motors only. BTW LM78XX will not work because it will need a 3V headroom to give 5V output so input is at least 8V and above. You could bypass the regulator and use usb only but I can't gaurantee performance or stability of arduino.

http://www.onsemi.com/pub_link/Collateral/NCP1117-D.PDF

I think 1117 needs 1.2V or so drop out voltage, and it can not withstand more than 20V (max operating voltage is 15V). So the board is designed to operate with either direct USB power, or 12V through 1117. 24V input will blow the board.

For the chip identification, I hold 95% possibility on it to be a 1117-5. Almost all cheap Chinese boards use 1117 for any voltage, because they're cheap, and SMT friendly, they are just modern 78xx.

In a way you can say it is modern 78xx but they are not interchangeble, usb 5V into 78xx will not work/regulate. 78xx series start at 5V output so 5V into 5V 78xx is too low as it needs extra 3V so minimum input is 8V. LDO primary application are for battery powered devices. That's why it will work when 5V usb is used as 1117 will continue to regulate even when input is down to 3.5V ( for 5V 1117 ). Very suitable for battery/handheld devices.

[tyguy2]

Well, I tried out a few options, and I think I'm just going to apply 5v. I'm using a 12v supply on the board, and when I put an LM117 on the correct pins, the board works perfectly. Since it works for what I need it to do, so I'm not too worried. Thanks for the help!

[JoeB83]

Well, I tried out a few options, and I think I'm just going to apply 5v. I'm using a 12v supply on the board, and when I put an LM117 on the correct pins, the board works perfectly. Since it works for what I need it to do, so I'm not too worried. Thanks for the help!

LM117 or LM1117? Both are voltage regulators, but the 117 is adjustable, and 1117s are fixed. Hopefully it's just a typo.

LM117: http://www.ti.com/product/lm117
LM1117: http://www.ti.com/product/lm1117-n