Datascope Passport 2, Руководство по обслуживанию

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Passport 2®/Passport 2 LT™ Service Manual 0070-10-0441 2 - 37
Theory of Operation Power Supply
On the Front End processor, it is crucial during power up that VDD never exceeds VDDH by
more than 0.3V. Within the processor, there are diode devices between the two voltage
domains, and violating this rule can lead to a latch-up condition. This is satisfied because it's
3.3V switching power supply runs off of +5.5V and has a slower startup, while VDDH, which
also runs off of +5.5V, is output from the voltage regulator, which comes up almost
immediately. So VDD will never exceed VDDH. Contingencies for enabling the +5V and -5V
by the microcontroller were removed to satisfy the power up sequencing on the VDDH line.
2.10.2 Part Number 0014-00-0251
The power supply can operate off of an AC line, a DC source from the Docking Station (DS-
DC), or two Batteries (either Sealed Lead Acid or Lithium-Ion). The power supply will
automatically select the available power source based on a specified priority.
The power supply provides 5V and 12V regulated DC output voltages. The outputs are
turned On/Off via a logic signal
REMOTE-ON* .
Two independent multi-chemistry battery chargers are included in the power supply. The
chargers are capable of rapid charging up to two Sealed Lead Acid or Lithium-Ion batteries.
The chargers will be activated when AC or DS-DC power is applied.
The power supply constantly monitors various available power sources, which are selected in
the following priority order:
1. AC, or DS-DC
2. BATTERY
The total off-state current from both batteries must be less than 5 mA. During Battery
operation, the
BATT-OP* output signal is set to a logic “0”. Otherwise, BATT-OP* is a logic
“1”. When operating on battery power, each battery will share the total load based on its
individual charge level.
The transfer from one source to another is seamless and occurs when the source providing
power is either disconnected or out of range.
An AC-PRESENT output signal that can drive an external LED at 10mA indicates the
presence of AC power. When AC power is applied, this output signal has an open-circuit
voltage of 20Vdc ±15%, with output equivalent impedance of 1.8k
Ω
±10%. When AC
power is not present, the AC-PRESENT output signal is 0V.
The power supply includes two independent chargers that are capable of charging 2 Lithium-
Ion (Li-ion) batteries (P/N: 0146-00-0069) or 2 Sealed Lead Acid (SLA) batteries (P/N:
0146-00-0043).
The chargers are enabled upon application of AC, or DS-DC power and are independent of
the
REMOTE-ON signal. The charger provides protection against shorted battery cells and
overly discharged batteries.