Appendix A 10/14/99
1 DC/DC Power Supply
1.1 Overview:
Atlas Model 622 and 623 can be powered either from AC or battery. A 50W, medical grade, offline
switcher provides 12VDC from a universal AC input (85VAC to 264VAC – 50/60Hz). The battery is a
rechargeable 6-Volt, 6.5 Amp-Hour, Sealed Lead Acid Battery, and will provide about 1.5 hours on a fully
charged battery (Battery Life depends on usage, especially printer usage, NIBP cycles, and CO2
operation).
The unit will operate from AC when the unit is plugged in, and switches to battery operation when AC is
removed. The battery is automatically charged whenever AC is connected.
The following supplies are generated on the Atlas Main Board:
+12V DC Input: Output of AC/DC supply or Battery.
Supply for CRT and miscellaneous analog circuits.
+5V DC Input: Output of Battery Charger or Battery.
Supply for front panel LED’s.
+3.3V DC Input: +5V DC
Supply for CPU board.
Backup Regulator: Input Output of AC/DC supply or Battery.
3.3V supply, for real time clock and On/Off circuits.
Battery Charger: Input: Output of AC/DC supply
Charge SLA battery.
+12V
AC Not Present
+5V
+3.3V
On/Off
AC Present
AC+12V
Battery
On/Off
Control
Circuits
+12VDC
Regulator
Battery
Charger
+5VDC
Regulator
+3.3VDC
Regulator
AC/DC
Converter
DC/DC Circuits
Block Diagram
D310
Q311
Q303
Backup
Regulator
1.2 On/Off Circuits
1.2.1 Backup Regulator and Micro-Controller
A 3.3V low backup regulator, U307, provides power to the On/Off circuits and provides power to the real
time clock on the CPU board. The On/Off circuitry is controlled by the mirocontroller U10. This
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