IBM Series 1 User Manual page 89

The power supplies for the processor and I/O expansion units
provide five regulated
DC
output voltages:
+5.0, +8.5,
+12.0, -5.0,
and -12.0
volts.
Both supplies contain
overvoltage, undervoltage, and overcurrent protection.
Should overvoltage or undervoltage occur, the condition
initiates a power supply shutdown sequence.
SegYgQ£ing
~~~i£~ment§.
The power-on reset signal is
provided to assure the state of
the
logic during power on
and off. The signal is TTL compatible. Logical one (up)
level is between +2.6V and 5.5V. Logical 0 (down) level is
between O.OV and +0.4V. The power-on reset signal starts at
the TTL down level. When the +5V, -SV, and +8.5V are within
operational limits, this signal goes to the TTL up level
after a 500 millisecond delay_
Should any of the three
voltages go approximately 3S below their minimum tolerances,
this signal goes to the TTL down level.
1Q,g.i£
yoltag~ ~~uencin,g_
If a user incorporates a
technology such that voltage sequencing must occur within a
given period of time (>350ms), the following method can
possibly be used. Assume
that,
for substrate biasing
purposes, Vn=-5.0V and Vh=8.5V;
if
Yn is more positive than
-3.5V, Vh must not remain above +5.0V for more than 500ms.
Although no true sequencing occurs, after approximately
350ms the power supply circuitry checks to see that the
voltages are at an operational level, if not, the supply
shuts
down;
otherwise the sequencing is met and
the
technology is protected.
2-74 GA34-0033
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