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Nokia charger

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bananasiong

New Member
Hi,
I have a nokia charger that its connector is not working anymore, so I use it as the power supply of my PIC programmer and my PIC experiments. I have a 5 V low dropout voltage regulator in it (5.5 V input max). On the charger, written the output DC 5.3 V, 500 mA. So I assumed that I can use the charger for my new programmer.
I was able to use it in my house. Today, I went to my college and measured the output voltage of my charger. It was 6.1 V!!!! I connected it to my programmer, and measured the voltage of the charger (with the programmer as the load), and the voltage is 5.9 V.
Luckily I didn't burn the voltage regulator, just wonder why the output voltage of the charger is higher than as rated. I planned to use it as the power supply of my programmer, and I have mounted the voltage regulator onto the PCB :eek:
Sigh, will I harm the little voltage regulator with input voltage higher than the rated??
 

audioguru

Well-Known Member
Most Helpful Member
Hi Banana,
A low dropout 5V regulator usually has a minimum input voltage of 5.5V. Its max input voltage is about 30V.
Which regulator is it?

An AC adapter doesn't have a regulated output voltage. It will be very high without a load, high with half its rated load and about the correct voltage when fully loaded.
I have a "9VDC" AC adapter rated for only 280mA. Its output without a load is 13.6V. Its output is 9VDC with its rated load but it gets extremely hot.
 

bananasiong

New Member
Hi,
It is TPS73150 from Texas Instrument. Its dropout voltage is only 30 mV and the datasheet says that the max input voltage are 6.0 V (under 'Absolute maximum rating') and 5.5 V (under 'Electrical characteristics).
I'm not sure whether my charger has regulated output or not, but it seems working fine with the voltage regulator.
Is that called AC adapter or DC adapter? The output is in DC, but the voltage is higher than rated.
 

audioguru

Well-Known Member
Most Helpful Member
You have the smallest voltage regulator that I have never seen.
 

bananasiong

New Member
I think that should be fine. 6.1 V is just a bit more than 6 V. With load added, the voltage is 5.9 V.
But there are two max input voltage rating in the datasheet which is confusing the user.
 

audioguru

Well-Known Member
Most Helpful Member
The TPS73150 regulator has a max temporary input voltage of 6.0V. They say it might not meet its spec's at such a high voltage and its reliability might be poor.
The max continuous operating input voltage allowed is 5.5V where it is guaranteed to meet its spec's and it is expected to last a long time.
 

bananasiong

New Member
Since I'm using it for programming, which takes me not more than 20 seconds, so I'm not going to remove it. I don't want to edit the PCB anymore :D
 
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