Hi,

I have an electronic board which doesn't work. It has a 7805 regulator which works well. That regulator is connected to an IC which has the mark "1020". The IC 1020 is SOIC-8 package. Pins from 1 to 4 are connected to 7805 output, and pins 5-8 are connected to the VCC of some TTLs IC.

When I measure voltage between VCC and GND in the TTLs IC, I don't get any voltage. So I think that the IC 1020 could be faulty because TTLs Vcc depends on this IC.

However, I don't know what kind of regulator is the 1020 because looking into the datasheet that I found (which I don't know if it's right), the 1020 is a Buck regulator. But I don't know why pins 1-4 are all shorted, and pins 4-8 as well.

I want to replace that IC, but I need to know exactly its function.

 

Link for the datasheet and a picture of the ICs would help. However, it doesn't sound like a buck regulator - you should see an inductor nearby.

 

Picture of the IC attached. I'm not sure about the datasheets that I found, that's why I don't attach the link. I have found different devices with "1020".

 

All I can say is it looks like a mosfet.

 

Picture of the IC attached. I'm not sure about the datasheets that I found, that's why I don't attach the link. I have found different devices with "1020".

It is likely a mosfet similar to the one attached. The SOIC-8 is a common size for low single amp MOSFET with your pinout.

http://www.mouser.com/ds/2/427/sq4080ey-1099779.pdf

 

It is likely a mosfet similar to the one attached. The SOIC-8 is a common size for low single amp MOSFET with your pinout.

http://www.mouser.com/ds/2/427/sq4080ey-1099779.pdf

According to this, the Drain is sourcing the TTL's IC? Do you think it could faulty or it need something else so it can supply the TTL's?

 

That mosfet ic is a switch that provides power from the regulator to the TTLs when a signal is applied to its pin 5. Think as being a relay. Power into pin 5 makes pins 1,2,3 connect to pins 5,6,7,8.
So probe pin 5 for its 'switch-on' command. Some microcontroller or circuit should be responsible for switching it on when certain conditions are met.

 

Yeah, mosfet. The clue is that it's labeled Q109. The voltage you are reading is because it's not turned on. Probably not part of the problem.

 

Perhaps a Hitachi HAT1020R.
http://pdf1.alldatasheet.com/datasheet-pdf/view/63527/HITACHI/HAT1020.html