3.14 5V PSU and 3.3V PSU
This starts with the 12V DC input from the
remote power supply. The switch mode down
converter is almost the same as the 6.3V
heater PSU. Differences are that it has no on/
off function but remains on all the time. The
feedback potential divider has different value
of course and the compensation network is
slightly different. Otherwise it uses the the
same chip, inductor and diode.
The 5V output is passed to a 3.3V low dropout
regulator.
Also note the negative input is connected to
two terminals marked chassis earth bond. If
the final case is metal then these connections
are used to connect the chassis and the
negative supply line must be earthed in the
remote 12V PSU.
These capacitors are added for local energy
storage for peak current demand, such as
when the flyback convertor starts. In practice I
have not found them to be critical.
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Содержание An E1T Timepiece
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