2-10 MAC 5500 resting ECG analysis system Revision E
2020299-020
Equipment Overview: Theory of Operation
Power Supplies
The MAC 5500 resting ECG analysis system requires several regulated voltages
for operation of its various components. The Main Regulator provides most of the
supply rails. The supply rails are:
+3V-C
MAC 5500 resting ECG analysis system is never truly “off.” The system
supervisor microcontroller (MOE) must constantly monitor the power key and
perform battery charging/gauging. The clock/calendar in the Super I/O chip must
also maintain time/date when the machine is off. These functions are powered from
the +3V-C rail, which provides power continuously from the battery pack regardless
of the state of the rest of the system. The Main Regulator produces +3V-C directly
from the battery rail via an internal low current linear regulator. Only 5mA are
available from +3V-C, so it must be used sparingly.
NOTE
The MAX782’s low current regulator is dreadfully inef
ficient. Regulator
Q
current appears to be about 3x the load current. This makes conservation of load
on +3V-C crucial.
+3V-M
Most of the MAC 5500 hardware runs from +3V-M. The MAX782 provides this rail
from the battery via a PWM synchronous switching regulator. Moe controls +3V-M
in tandem with +5V-M.
+3V-EMI
This is simply an RF blocked feed from +3V-M. +3V-M load is contained within the
CPU board. Power for devices for external functions is supplied by +3V-EMI. The
isolation of +3V-EMI from +3V-M may be unnecessary as the concept has never
been tested for its effect.
+5V-M
The MAC 5500 resting ECG analysis system is not fully in the 3V age. The Super
I/O and thermal printhead require 5V power. The MAX782 provides this rail via
another PWM synchronous switching regulator. Moe controls +5V-M in tandem
with +3V-M.
+5V-EMI
Similar to +3V-EMI, this rail is an RF blocked feed from +5V-M, used to power
devices for external functions. The isolation of +5V-EMI from +5V-M may be
unnecessary as the concept has never been tested for its effect.
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