This component is likely some sort of power transistor, but the markings a very small and hard to read because of the reflection from the conformal coating.

package: SOT223 (black 3-pin SMT package with cooling flange)
markings: IY20903 (very uncertain about this, very hard to read) newline 112115
pcb-id: LIC110 (visible in photo below pin1 of component)

Please have a look and see if you can identify it. I had no luck with many online searches. Thanks.

enter image description here

  • \$\begingroup\$ The image is too dark. \$\endgroup\$
    – winny
    Dec 28, 2023 at 8:32

1 Answer 1


I think it's a Analog Devices LT1121IST-5 LDO and the actual marking is


(the 'e3' is not always rotated like in the image, see for example LT1117IST) enter image description here

(Source: alibaba.com)

Here is my reasoning:

  • The pinout is reasonable
  • The designator LICxxx makes more sense for a LDO regulator than a transistor
  • The Linear Technology 'LT' logo could be interpreted as 'IY' under conformal coating (especially with the old marking style, see last picture)
  • If 'e3' is not roated, the top line would read LT + 5 characters like described
  • The bottom line '1121I5' is very close to what is described
  • The last '1' in your picture looks more like an 'I' to me

A picture of the LT1117IST as reference, I think your part uses this older marking style:

enter image description here

(Source: lcsc.com)

  • \$\begingroup\$ Great detective work. Your analysis looks very promising. I'll do some measurements tomorrow and see if that might confirm the identity. \$\endgroup\$
    – reikred
    Dec 28, 2023 at 8:12
  • \$\begingroup\$ I think answer is correct, thanks much. \$\endgroup\$
    – reikred
    Dec 29, 2023 at 23:16

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