Trying to indentify a voltage regulator.

[jsbush]

I think I have a voltage regulator thats blown. One of them lets battery power through one way, but doesn't let ac power through the other way.

I just want to identify the IC so I can get the datasheet and test it some more.

Here are the markings

4890
AK?
L57A

It's 8 pins, 4 on each side. I can't make out the manufacture logo.

 

[PottedMeat]

The # 4890 is probably part of the part # unfortunately it's also used with ATI's Radeon 4890. A photo would probably help a lot.

Can you shine a bright light on it and make out a mfr's logo?

ex.

Is it a 'i' with a circle = infineon
texas shaped blob = texas instruments
'I' arrow down 'F' = international rectifier
'F' = Fairchild

 

[jsbush]

Well I can kind of.

Logo is a rectangel, inside is a black dot with circle under it. like the letter "i" but with a circle instead of the line under the dot.

Sounds like its infineon like you mentioned thanks.

 

[jsbush]

Just looked at the logo of infineon, and it's not the same. It's kinda of like this ö but with one dot on top of the o, and thats indside this rectangular wave shap, kinda of like a sheet of paper.

 

[Modelworks]

Look here to try to match the logo:
http://www.dialelec.com/semiconductorlogos.html

It sounds like Seiko to me.
http://www.sii-ic.com/en/index.jsp

 

[William Gaatjes]

Originally posted by: jsbush
I think I have a voltage regulator thats blown. One of them lets battery power through one way, but doesn't let ac power through the other way.

I just want to identify the IC so I can get the datasheet and test it some more.

Here are the markings

4890
AK?
L57A

It's 8 pins, 4 on each side. I can't make out the manufacture logo.

Hello, would you be so kind to make a picture of the circuit board ?

I would like to see the surrounding components.

I am thinking this is the component but i am not sure...


ml4890

 

[jsbush]

Here are some pics. But after further testing i'm not sure it is the voltage regulator anymore. I'll explain in another post, here are the pics.

PA150003.JPG
PA150005.JPG

 

[jsbush]

Check out these pictures, I have details of problems I have found. It seems like whatever tells the charging system to turn on when the battery needs charging isn't turning on. The rest seems fine.

I get very similar readings, and resistance on almost everything, except a few things which I'm assuming are a result of the charging system not turning on.


PA150003-1.jpg
PA150005-1.jpg


I checked all the fuses, which seem fine, including the PF's. I have an identical board to compare to.
Any idea's? The problem started after a short in the power connector. (battery wouldn't charge).

 

[schenley101]

this might be it? good luck

http://www.core-ic.com/quote.p...16L57A&company=CORE-IC

 

[Modelworks]

I would check the fets on the board. You may have to remove them to test them.
Looking at the data sheet of the maxim chip it looks like a good place to start. I would start with that chip and work outwards using page 16 of the data sheet as a guide.
http://datasheets.maxim-ic.com...ds/MAX1908-MAX8765.pdf

 

[PottedMeat]

Ok, the pictures help a lot for identification - the logo is a S with an 'i' in the middle - Vishay/Siliconix.

You can usually tell SO8 packaged single MOSFETs by the 4 shorted on one side ( drain ), 3 shorted on the other ( source ), and the single gate terminal.

SI4890 - N-MOSFET http://www.vishay.com/product?docid=69502&query=si4890

it's probably paralleled with the other SI4890 and bridged with the SI4430's ( P-MOSFET ) for a synchronous buck converter.

 

[schenley101]

I think that it is a Siliconix vr. the log is close and the naming scheme is similar, however now, there power ic package number is on to 5XXX.

 

[Modelworks]

The data sheet shows 4 N and one P fet which is very close to those pictures. A lot of manufacturers will use the reference designs of an ic if they can, saves them extra work. Anyway a good starting point.

 

[jsbush]

Here's where i'm at in trouble shooting;

could it be the 4435B IC that is bad?
Take a look at the pic.
PA150003-2.jpg

 

[jsbush]

Originally posted by: PottedMeat
Ok, the pictures help a lot for identification - the logo is a S with an 'i' in the middle - Vishay/Siliconix.

You can usually tell SO8 packaged single MOSFETs by the 4 shorted on one side ( drain ), 3 shorted on the other ( source ), and the single gate terminal.

SI4890 - N-MOSFET http://www.vishay.com/product?docid=69502&query=si4890

it's probably paralleled with the other SI4890 and bridged with the SI4430's ( P-MOSFET ) for a synchronous buck converter.

They look very much like that.

 

[jsbush]

Ok it's not the 4435B.

Somewhere when the ac and battery are plugged in gives a 3volts and turns off the 12 from battery, then that turns off the 12volts running to the 4435B and lets the voltage through to the other side.

Here's how it works on my good board.
PA150005-3.jpg
PA150003-3.jpg


Here's my bad board.
PA150005-4.jpg
PA150003-4.jpg

 

[Colt45]

It looks like the maxim chip is controlling the fet...
http://www.datasheetcatalog.or...heets2/90/900322_1.pdf

See page 14: AC_OK pulls down the Pch FET's gate (your 4435B) ["P1" in the drawing], and allows the unit to run off the AC adaptor, else off battery.

If the voltage at the pin AC_IN (which is DC, what a misnomer) is greater than 2.048V (1/2 of the int. ref), it drops /AC_OK. (which pulls down the gate @ 4435B), and enables operation from the ac adaptor. So check the voltages at those pins for starters. (don't slip..!)

edit:
So, if the voltage at AC_IN is less than 2.048V, [ac adaptor] power isn't getting to the maxim chip, and you need to figure out why. If it is, AC_OK should be low, if it isn't, there's likely a problem with the maxim chip.

If AC_OK is low, there must be a broken trace or cracked resistor or bad joint between it and the FET, or the gate of the 4435B is shorted to +12V (either external or internal to the FET...)
Check the REF pin too, it should be 4.096V.

Check the resistance between the gate and drain or source on the 4453B, that should rule out a short and the FET being the problem. SWAG says maybe something in the 5K-20K area, not too important, as long as it isn't short (or close to it).

 

[jsbush]

Hmm.. Ok so AC OK is low. You have me lost at with the FET. Right now I guess I should be tracing from ac ok, to look for where the problem starts.

At AC IN I get 2.248v. At AC OK I get 3.3v with ac out, and 0.80v with ac in. REF I get 4.07v


Edit: I tested my 4435B and it seems to work just fine.

 

[bobdole369]

Has noone noticed the melted freakin inductor yet? THat baby got HOT!

 

[William Gaatjes]

I am unable to open these foto's...

You tried to access the address http://pics.bbzzdd.com/users/jsbush/PA150005-3.jpg, which is currently unavailable. Please make sure that the Web address (URL) is correctly spelled and punctuated, then try reloading the page.

That's all i get to see.

Anyone else got difficulties too opening these pictures ?


EDIT:
Fixed it, Firewall was to protective .

 

[William Gaatjes]

Originally posted by: jsbush
Hmm.. Ok so AC OK is low. You have me lost at with the FET. Right now I guess I should be tracing from ac ok, to look for where the problem starts.

At AC IN I get 2.248v. At AC OK I get 3.3v with ac out, and 0.80v with ac in. REF I get 4.07v


Edit: I tested my 4435B and it seems to work just fine.

Well, those voltages seem within tolerance.

If understand correctly your device powers up from battery but not from ac in ?
If that is the case, the maxim is just a charger, it does not intelligently switch the power.
If this is a laptop, then most of the time a small dedicated microcontroller does that. But i admit this is old knowledge. Highly likely that from the ac_ok pin some circuit switches a power fet on and off (the ones inside the small 8 pin houses : SO-8 or SOIC-8)That powerfet switches the adapter pin power to the input of the switch mode power supply somewhere located on the pcb. Best thing to do would be indeed to follow the ac-ok pin and try to draw the circuit on paper. A bit of reverse engineering to understand what the circuit does so you can fix it. Best way is to compare it with the good pcb and draw a circuit from the good pcb. Then use that information to trace back on the bad pcb.
Most likely, the fet's that switch the adapter power are P-mosfet's.

Pages 13 and 14 of the maxim datasheet are interesting.

The white components called PF4 and PF6 are higly likely polyfuses. These are fuses but made of PTC resistor material. These fuses should be near 0Ohm when cold and ok. You could check them with the good and the bad board with power applied. IF one of those trips, you have a short circuit somewhere.

 

[jsbush]

After a short in the power connector, the laptop stopped sensing the battery. When AC is not plugged in, with a charged battery, computer shuts down on a critical low battery error. (only on boot up, once in OS its fine)

Something broke during the short, that either stopped sensing the battery all together. Since it doesn't know the battery is there, it doesn't turn on the battery charger.

Here are more problems i found while tracing from the AC OK.
PA150003-5.jpg
PA150005-5.jpg

 

[William Gaatjes]

Originally posted by: jsbush
After a short in the power connector, the laptop stopped sensing the battery. When AC is not plugged in, with a charged battery, computer shuts down on a critical low battery error. (only on boot up, once in OS its fine)

Something broke during the short, that either stopped sensing the battery all together. Since it doesn't know the battery is there, it doesn't turn on the battery charger.

Here are more problems i found while tracing from the AC OK.
PA150003-5.jpg
PA150005-5.jpg

That is not easy. To start somewhere, the schematic on page 14 of the maxim datasheet would allow a short of the powerconnector causing high currents to flow. If there are really polyfuses used, these currents should not get too high but maybe it is a design flaw.

It could be that the sense resistor is damaged. In the schematic that would be RS1. The sense resistors are really low in resistance so they will be difficult to measure. But a possibility is the following path : P1,RS1, N1A,N1B,RS2, L1 . These are components in the schematic on page 14. The IINP output represents the current drawn from the (ac) input.

 

[William Gaatjes]

I think the easiest way is to use a oscilloscope to check if the max8724 at least does something. On PIC 150003-5 you mention that 1 component has 1.5V at a good board and 0 volt at a bad board. Could you check if this is a dual p fet. What is it's marking ?
If it is a dual p fet, then likely there is a square-wave present on those pins. Because 1.5 Volt sounds to me like a square-wave.



EDIT:

The SI4435 is a P-Mosfet. This means that the pins called "s" or "source "must be more positive then the pin called "gate" in order for the mosfet to conduct electricity from source to drain.

The SI4890 is a N-mosfet. This means that the pin called "gate" must be more positive then the pins called "s" or "source" in order for the mosfet to conduct electricity from drain to source.

Looking at picture 150003-1 : I have difficulties interpreting what you mean. If i read correctly , it means that on the defect board PQ53 does not switch when looking at how the copper traces connect to the row of capacitors. You must start from the ac pin and look from there on the mosfets that are connected to the ac adapter input.

When looking at the pictures, i notice there are 2 battery connections ?
Are there also 2 max8724 ic's ?
If not then the charger is switched between the 2 batteries.

If there are 2 battery connections, have you checked what the pcb does when connecting 1 battery to a connection at a time ?
Let me know, i am getting curious

 

[blahblah99]

Originally posted by: jsbush
I think I have a voltage regulator thats blown. One of them lets battery power through one way, but doesn't let ac power through the other way.

I just want to identify the IC so I can get the datasheet and test it some more.

Here are the markings

4890
AK?
L57A

It's 8 pins, 4 on each side. I can't make out the manufacture logo.

They're not voltage regulators.

Looks like some sort of mosfets to me. You can tell by the copper pours joining the opposite sides of the ICs.

If I were to bet, I'd say those are fets for a switching power supply.