# Input Voltage Limit

Hey guys i am currently working on a project and i need to use 19v as an input voltage i know that 6 to 20 volts is absoluete maximum so it should be fine? But a while back i made a project using 12v as input voltage and the regulator was getting really hot so can using 19v damage the regulator has anyone tried that?

The power dissipated by the regulator is the product of the voltage drop and the current. So although 19V is under the limit (only just, and over the recommended) you'll be dropping 15V to get to the required 5V and then you times that by the current to be drawn. That will give you quite a lot of heat...

But have to ask: why do you "need" to use 19V? Using an old laptop charger?

Yes i wanted to use an laptop charger seems like i need to use another type of power source thanks for the help

Please dont use anywhere near 20V as the forum is littered with topics regarding how to replace regulators on blown boards.

Average suggestion seems to be around 9V.

Read the datasheet characteristics for the current regulator being used, NCP1117 http://www.onsemi.com/pub_link/Collateral/NCP1117-D.PDF Note 3 on page 2: 3. The regulator output current must not exceed 1.0 A with Vin greater than 12 V.

Characteristics on page 3: 5.0 V (Vin = 7.0 V, Iout = 10 mA, TA = 25 °C) (Vin = 6.5 V to 12 V, Iout = 0 mA to 800 mA) (Note 4)

12 V (Vin = 14 V, Iout = 10 mA, TA = 25 °C) (Vin = 13.5 V to 20 V, Iout = 0 mA to 800 mA) (Note 4)

Greater than 12V is not really in spec. Might have been a little higher with the earlier MC33269 5v regulator, but even that shows Current Limit (Vin − Vout = 10 V), so 15V Max on Vin.

20V should not be shown on the Product page in my opinion.