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Hello i have what looks to be a PNP transistor.The marking code on it is U3W with the numbers 65 rotated 90 degrees next to U3W.Its a Sot-23-3 package,refer to image of schematic of how its connected.

Pin A and Pin B are from a RS-485 transceiver,and another note the A,B pins are used to send DMX512 data across it.

Firstly could this be a transistor based on how its connected?If it is do you happen to know the part#,or company,etc?Any input is appreciated thanks.enter image description here

http://www.ti.com/lit/ds/symlink/sn65176b.pdf

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    \$\begingroup\$ Your schematic says it's NPN, but your text says it's PNP. Which is it? \$\endgroup\$ – ThreePhaseEel Aug 2 '17 at 2:21
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    \$\begingroup\$ You're sure it's not a dual diode, used for over and/or undervoltage or ESD protection? \$\endgroup\$ – The Photon Aug 2 '17 at 2:30
  • \$\begingroup\$ Yeah, I was thinking dual TVS diode myself...but if it's reading like a PNP, then it's the wrong way 'round to be a dual TVS... \$\endgroup\$ – ThreePhaseEel Aug 2 '17 at 2:36
  • \$\begingroup\$ Not that a simple common-cathode dual (zener/tvs/...) diode would work for RS-485, but there are lots of different kinds of protection parts out there. \$\endgroup\$ – The Photon Aug 2 '17 at 2:43
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    \$\begingroup\$ @ThreePhaseEel It is a PNP. \$\endgroup\$ – blinded_ravager Aug 2 '17 at 3:24
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It seems likely the part is some kind of ESD and/or over-voltage protection device.

For example, something like CDSOT23-SM712, which has asymmetric clamping voltage that seem to be pretty well matched to RS-485 (which can go to +12 V positive but only -7 V negative).

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  • \$\begingroup\$ FWIW, WU3 rather than U3W would likely be Nexperia's PESD15VS2UT but this wouldn't deal well with negative signal voltages. \$\endgroup\$ – The Photon Aug 2 '17 at 3:02

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