Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

[ngth82]

Well, this is worth a try:

This comes from a hp monitor board R0171-2281-0112 on an "HP 27f" IPS display. The original owner of this display plugged in the wrong power adapter and the SMPS SOIC8 blew up and burnt some of the board fiberglass below. I found a replacement FR9889 SOIC and installed it at location U1, that got the +5.2V supply working.

However, there is a short down the line. I removed the ferrite "FB2" to isolate the 5.2V supply - which seems fine.

Downstream of the ferrite, i found the short on a SOT23-5 pin part (U4).

I'm trying to identify the part with the following markings. This used to be populated at location U4. (please refer to the picture):

First line: "FA2hFA"
Second line " __._"

The second line consists of two underscores, a period and an underscore. The period lines up with the lowercase 'h'

The upper right pin is +5V.
The lower middle pin is ground.

C145 is the high freq decoupling cap

[redwire]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

SMD marking code FA2hFA SOT23-5 might be AX6607 adjustable LDO.


Did you ID the other part, SOIC-8? A polarized filter, or wetting the top with IPA, or light from a side angle can help a lot trying to read IC numbers.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Good morning @redwire -

Wow, I'm happy to see a reply on this thread I briefly looked at the datasheet that you pointed you this morning. I'll have a greater opportunity to examine the components around U4 on the board and see if this aligns.

Thank you for the lead!

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Did you ID the other part, SOIC-8? A polarized filter, or wetting the top with IPA, or light from a side angle can help a lot trying to read IC numbers.

Yes, i already ID the other SOIC8 - that is a FR9889 SVR and got a replacement for it.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

I was able to spend a little bit of time looking at the board this evening.

According to the AX6607 datasheet, the pin numbering goes counter clockwise, and starts in the bottom left corner (the side with three pins). Lets go with the AX6607 for this discussion:

Pin 1 - VIN
Pin 2 - GND
Pin 3- EN (high)
Pin 4- FB (adjustable version)
Pin 5 - VOUT

I ohmed the pads out:

• Pin 1 (VIN) and Pin 4 (FB) are connected - 0 ohm. (noted in red lines) When i plug in the board without the part installed, both of these pins reads as 5V.
  
• Pin 2 is ground (noted as green lines).
  
• Pin 3 is connected through L12 (ferrite bead) and traces to R185 (top left resistor, the reference designator silk is cut off). The cap, C85, is in parallel and is not populated (The connectivity of these components are noted in orange lines)
  
• Pin 5 is theoretically the output according to the datasheet. Instead, I see the resistor divider network - R161 (right hand goes from Pin 5 to ground). R185 (left hand side, goes from Pin 5 to the orange node previously mentioned. The via immediately "north" of Pin 5 goes to the bottom and there is a test pad.

Here's where the problems start:

• If this is really an AX6607, pin 4 (FB) should be the shared node for the resistor divider for R185 and R161. This shared node is on pin 5.
• Pin 1 and pin 4 are shorted - VIN and the FB pins are never shorted in a LDO.

Is there a possibility this can be a different part with similar markings?

Thank you
Thomas

[redwire]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

I agree, the PCB seems to have a different pinout, possibly:
Pin 1 - EN
Pin 2 - GND
Pin 3 - IN
Pin 4 - VOUT
Pin 5 - FB

None of mainstream SOT23-5 LDO's have this pinout - they are all flipped, so pin 5 is OUT, 4 is FB etc. For 5V you don't need an adjustable version.
The only other IC with "FA" in the marking code I can find is ETA5050 and RT9193, EUP7967 are also similar but different marking codes.

Unless we're out to lunch and this is a buck regulator with inductor on pin 4? Then the part might be marking code "FA2" FP6381A.

[R_J]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Could it be similar to a Texas Instruments TLV62565 step-down converter

[lti]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

This does look like a buck regulator. The two parts above look correct, except that this board has a via connected to pin 3. On those two parts, pin 3 only connects to the inductor (L12). Can you see any connection to pin 3 on the other side of the board? If not, it might just be a via to nowhere acting as a test point.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

It's been a crazy work week... i'll have more time to look at this board on Saturday.

I did get a few minutes to check it out again. U3 (directly north of the part in question) is the same SOT23-5 with the FA2hFA marking.

But there are differences.

Pins 1 & 4 are NOT shorted together.

I'll take my hot air gun and remove U3 then examine this under the microscope.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

This does look like a buck regulator. The two parts above look correct, except that this board has a via connected to pin 3. On those two parts, pin 3 only connects to the inductor (L12). Can you see any connection to pin 3 on the other side of the board? If not, it might just be a via to nowhere acting as a test point.

Hi lti - The via on the pin 3 power shape is indeed a test point on the back side. I see a via plus a small test pad. It doesn't have a connection to the copper shapes adjacent to it.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Maybe it will help to ID components a bit further downstream. There is a 128-pin TQFP - appears to be a video chip based on the connectivity. The identification mark says "TSUMO88CDT9-1" or "TSUM088CDT9-1"

• The bottom left four differential pairs goes to an HDMI connector
• The next four go to another HDMI connector.
• The bottom right corner goes to the VGA connector.
• The top row of differential pairs is the LVDs cable to the LCD display panel.

If we can ID the part and get a datasheet, we can figure out the function and output voltage of the FA2hFA parts -- but i generally agree it looks like an LDO - just with the wrong pinout.

One of the pins is connected to the left side of C104 & C108, and ohms out to the left side of L12.

C111 ohms out to the left side of L13.



Trying to find random parts from overseas suppliers is proving to be difficult

Thank you,
Thomas

[R_J]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

I did get a few minutes to check it out again. U3 (directly north of the part in question) is the same SOT23-5 with the FA2hFA marking.

But there are differences.

Pins 1 & 4 are NOT shorted together.

I'll take my hot air gun and remove U3 then examine this under the microscope.

It could be that pin 4 is VIN and pin 1 is enable, on the one regulator pin 4&1 are connected because it's output is ON when there is VIN
The other regulator likely has VIN all the time but its output is switched on with the enable pin by a power control circuit.
It could be that pin 3 is the SW (output)

[R_J]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

After more searching, I believe the ic is a fitipower, FP6381AS5CTR, like this one. The TI tlv62565 seems to be the same

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

After more searching, I believe the ic is a fitipower, FP6381AS5CTR, like this one

WOW. Where did you end up coming across this one? I think we have a winner.

The package comes in SOT-23-5, SOT-23-6, and TSOT-23-5. Looks like they are all footprint compatible - the SOT-23-6 just has a power good signal between pins 4-5. The TSOT-23-5 is just thinner, but looks to have the same footprint as the SOT-23-5.

As far as the resistor divider network goes (measured in-circuit):

R185 (between Vout and FB node) is ~53kOhm
R161 (between the FB node and ground) is ~33kOhm

Vout = 0.6V * (1+ R185 / R161)
Vout = 0.6V * (1 + 53K / 33K)
Vout = ~1.5V


I wasn't able to find a local source for this part, eBay has it available internationally. At least i can work with this knowledge though. I think i have a few TI SVR eval boards in my parts bin. I'll find one that supplies up to 1.2A and deadbug it into the circuit. I'll remove the FB components and measure them out of circuit to make sure the values are correct.

That should work for now. At least i should be able to reassemble the monitor and see if it fires up, or if the original surge did anything else to it.

Thank you for all of the help. I'll report back when i get a chance.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

i pulled the resistors and measured them out of circuit.

Vout = 0.6V * (1+ R185 / R161)
Vout = 0.6V * (1 + 179K / 38.9K)
Vout = ~3.3V

This is easy enough - i have a TI TPS62130 EVM that outputs 3.3V without mucking with the FB resistors. I'll just hook it up to +5V for VIN and to the left side of the inductor on the output plane.

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Success! The monitor powered on.

I piggy backed a TPS62130 TI evaluation board on to the 3.3V output - left side of L12 (i used C16).

The input was soldered across C128 - next to the SOIC-8 (5V supply).

The first image shows the evaluation card.
The second and third image shows the board connected up to the monitor. The power indicator on the front panel turns on and the backlights are on.

I was working on the floor, so i wasn't able to easily get a photo of the screen - but i saw it power up and display the "no signal" message. Good enough for now.

I'll dead bug a smaller board on to 3.3V then button up the monitor. The board needs to be placed into a cage that is fairly short.

Thanks for the help!

[R_J]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Or try a tlv62565

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Or try a tlv62565

Nice, thanks for pointing that out. I apparently missed it when reading the reply.

[redwire]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

I mentioned it earlier but scarcely available

[ngth82]

Re: Need help identifying "FA2hFA" SOT23-5 (5 pin SOT23)

Hey red wire -

Yeah, now I see it in Post #6 - sorry I missed that suggestion. It was spot on.


Out of curiosity, which sites do you guys use for case marking codes besides looking at the first few characters on a google search?

Thanks again