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Unread 04-02-2004, 20:42
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Dale(294engr] Dale(294engr] is offline
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FRC #0294 (Beach Cities Robotics)
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Exclamation Vishay34840 IR Rcvr Vout Fail +5v transition to 2.5v s/b 0v

Has anyone experienced IR Rcvr 4840 failures?
(i.e. output pin gnd level faill to go to 0v)

We've experienced 2 failures in two days.
Logically (code perspective), fault appears as a rcvr that never sees IR beacon, i.e. always high

Using oscilloscope to view Vout:
observe +5v = no IR, 0V pulse = normal 40 kHz detected (1 or 2 mS long)
Failed mode = low voltage transition falls short of 0v by ~2.5v.
Waveshape is sharp, just voltage level failure.
Fault appears equivalent to 30K resistance inside the 4840,
in series with collector. prior to Vout pin (voltage divider to gnd)

May have happened during scope probing,
either brief short to adjacent pin(s) or maybe ESD (static?)
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