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FMC DIO 5ch TTL a
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Opened by Erik van der Bij@erikvanderbij
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V1-1 - Pull up resistors not strong enough to disable outputs at startup

The 10 kOhm pull up resistors (R1, R11a/b, R12a/b) are not strong enough to disable outputs at power up. Therefore the design is out of spec.
Issue found by Seven Solutions.

Specification of outputs:

  • Output levels: LVTTL, capable of driving +3.3 V over a 50-Ohm load. At power-up the outputs should be in Hi-Z state
  • Withstands a continuous short-circuit on all the outputs at the same time

Action:

  • Replace R1, R11a/b and R12a/b by 4k7

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