Marquette Hellige GmbH MAC 1100/1200 V 1.1 Page 13
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2.3.1 Generation of internal power supplies
Logic power supply + 5V and + 3.3V
The processor core and the memory is a fully + 3.3V design.
The interface functions to display, to RS-232, to the printing unit and to the ECG
acquisition unit are supplied with + 5V.
Both the + 3.3V and the + 5V are generated separately by a clock-rated voltage
controller. By using the „adjustable version“ of the voltage controller, both supplies
are based on the same voltage controller. The output voltage is determined by
appropriate dimensioning of the voltage divider at the feedback input of the voltage
controller.
Standby supply + 5VSTB and + 3.3VSTB
The standby supply + 5VSTB supplies the ON/OFF Control, the + 3.3VSTB buffers
the patient ECG memory when the device is turned off.
Both supplies are generated together from one low-power linear regulator with low
quiescent supply current.
Analog supply + 12V
+ 12V is used for the heating control and temperature monitoring of the printing unit,
which requires only a current of a few milliamperes.
This supply is generated by a linear regulator with feedback input.
2.3.2 Switch On/Off circuit
The Switch On/Off Circuit consists of the On/Off Control and the Voltage Control.
The On/Off Control switches the device on or off by switching the device supplies
+UVERS and +USUPPSW.
The On/Off Control is supplied from the + 5VSTB.
Device On Sequence:
The transition from Device Off State, or Standby State when line power is connected
to Device On State can only be activated by pressing the On/Off button.
Device Off Sequence:
The transition from Device On State to Device Off State, or Standby State when line
power is connected can be achieved as follows:
pressing the On/Off button
when the control core activates the signal DEV_OFF,
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