I found this 6 pin PWM IC in one of the SMPS. I am unable to find any of its details on Google. I am requesting if anyone could help me finding the device name. The marking is something like FA=606 or 1FA=606.

Photo of PCB showing unknown device

  • \$\begingroup\$ Details on what is connected to each pin would be helpful. \$\endgroup\$ – Tom Carpenter Sep 26 at 9:44
  • \$\begingroup\$ PIN 1 - GND, 2 - FB, 3 - NC, 4 - SENSE, 5 - VCC, 6 - GATE \$\endgroup\$ – SUJIT MISHRA Sep 26 at 10:23
  • \$\begingroup\$ FA could be a former Fairchild reference like a FAN 60x but I could not find a reference corresponding to your marking. The pinout you describe is however common to many TSOP-6 PWM components. The NCP1253 could certainly do the job if you're looking for a low-voltage die. \$\endgroup\$ – Verbal Kint Sep 26 at 12:12

TL;DR; It's likely a Richtek R7735GGE PWM flyback controller.

There are many controllers in this format all with the same package (SOT23-6) and similar pinouts, so it's hard to narrow down the exact ones. So a bit of sleuthing was in order.

Most of them seem to use a similar format for their markings, something along the lines of ###YWW where ### is some short code for the series, sometimes two, sometimes three characters, Y is the year code, and WW is the week code in the year of manufacture.

So what we are looking for is something with a part code beginning with FA, and possibly FA= but that seems a bit odd for a part number. A bit of searching led me to this rather old document, which gives FA but for a completely different form factor which is a bit upsetting. However what it does show is part numbers that are ??= - the very strange equals sign, which seemed like too much of a coincidence to ignore.

Some hunting around for Richtek SOT32-6 PWM controller images led me to this:

Picture of PWM Controller with 1FA=### part number
Image Source

Aha, we have a part marking of |FA=S03 which is the same strange part number, but with a different year code. I've including the questionable 1 character which looks more like a | on this image, and may well be simply a pin 1 end marker (sometimes packages are marked with a line across the end which has pin 1 rather than a dot).

That gives us RICHPOWER (a.k.a. Richtek) R7735GGE. Now the full datasheet for that doesn't list the marking, it just says contact your local distributer, so I can't directly confirm my hunch, but it seems pretty solid from the anecdotal evidence.

From a pinout standpoint we have below, which matches sufficiently with the names in your comment:

1 - GND
2 - COMP (voltage feedback from opto coupler)
3 - PRO (optional external protection for overtemp or voltage)
4 - CS (current sense)
5 - VDD
6 - GATE (output to external FET)
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  • \$\begingroup\$ p.s. That one was quite a fun challenge. Keep 'em coming. \$\endgroup\$ – Tom Carpenter Sep 26 at 16:40
  • \$\begingroup\$ Thank you sir for your hardwork & research but I think I am not that lucky. I am unable to find any distributor for Richtek in INDIA nor this part is available on mouser, digikey and element14. Anyway once again thanks for your research. \$\endgroup\$ – SUJIT MISHRA Sep 28 at 6:13

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