Datex-Ohmeda 7900 Service Manual page 31

2/Theory of Operation
The charge time for the sealed acid battery, from a discharged state to full capacity
is 10 hours maximum.
• Charge levels
• Bulk charge current
• Over charge voltage
• Floating charge voltage
• Auto Charger Disconnect
• Auto Charger Disconnect Release
ac to Battery Automatic Switch Circuit
• Battery connection
• Battery standby current
Multiple Outputs dc to dc Converter
A single dc bus voltage, either from the ac to dc converter or the battery, is the input
to a dc to dc converter (MAX 796) similar to that used in the ac/dc section. The
converter has the five outputs required by the system at appropriate power levels.
Post low-drop regulators provide the most effective local regulation and high effi-
ciency with over current limiting and thermal shutdown protection. The 15V and
5RS_VAUX outputs are 10VA limited and go through 10VA limit circuitry before be-
ing sent to the SIB board and the pneumatic isolation area.
Voltage Rails Specifications
Outputs
• Digital logic
• +15V
• -15V
• EL Display
• VAUX
Ripples
• 5 VCC
• 5.5 Vdc
• 12 Vdc
• ± 15V
1503-0151-000
5 Vdc +3.685% to -3.05% 5W Max.
15 Vdc +15.75 Vdc to + 14.25 Vdc 2W Max.
-15 Vdc -15.75 Vdc to -14.25 Vdc 2W Max.
10 to 15 Vdc 10W Max.
5.8 Vdc 6.09 Vdc to 4.99 Vdc 7.7W Max.
3/27/97
Bulk charge, over charge and tempera-
ture compensated floating charge
250mA (c/10).
o
14.7V at 25 C
o
13.7V at 25 C.
7.56 to 8.08Vdc.
7.71 to 8.71Vdc.
Direct on dc bus.
< 200 uA.
< 50 mVp-p
< 100 mVp-p
< 200 mVp-p
< 100 mVp-p
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