GE MAC 1200

GE Medical Systems MAC 1200 V 1.2 Page 13
Information Technologies 227 492 21 Rev F
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:
mM pressing the On/Off button
m when the control core activates the signal DEV OFF,
E when the voltage control applies the signal REG OFF , because the battery voltage
gets too low during battery operation.