Ecg Recording And Front-End Processing; Controller Core - GE MAC 1200 Servicing Instructions

GE Medical Systems MAC 1200 V 1.2 Page 14
Information Technologies 227 492 21 RevF
The Voltage Control controls the battery voltage during battery operation.
The signal BATT_LEV2 indicates that the battery charge has gone down, and the device
should be connected to the line power soon.
The signal BAT_LEV1 indicates that the battery has been discharged almost completely,
the device should be connected to the line power immediately, otherwise the device will
shut down within few minutes.
If battery discharge is continued without connecting to the line power, the signal
REG OFF is activated and the device is switched off.
2.3.3 ECG recording and front-end processing
The patient input is classified as being cardiac floating and is defibrillation-proof.
The patient leads are connected with a 15-pin connector with a special form for the
specified and released patient cables for the MAC 1200.
The main element of the ECG recording and front-end processing is a set of chips
comprising 3 ASICs. Pace detection is realized by a separate circuit.
Every disconnected electrode is detected by a special AC measurement, which allows
higher impedance between electrode and patient.
N common-mode compensation ensures suppression of interference, at the same time
serving to improve the in-phase suppression of the input electrodes.
To protect patients, the ECG recording and front-end processing are assembled as floating
components. Digital signals from and to the controller core are transmitted via opto-
electronic couplers. The floating supply +/- 5V is generated by an isolated flyback converter
from the + 5V logic power supply.
2.3.4 Controller core
The actual core comprises the Motorola Power PC MPC821, which contains the following
integrated components:
m chipselect logic
m DRAM controller
m SCC and SMC for RS-232
m LCD controller
m SP! Interface