Figure 9-4: Power Supply Block Diagram; Figure 9-5: Display Control Block Diagram - Mallinckrodt Nellcor N-20PA Service Manual

Technical Supplement
9-4
On/Off
button
Power
Disposable
control
batteries
4–6 VDC
circuits
AUX PCB

Figure 9-4: Power Supply Block Diagram

• Display Control Block Diagram (Figure 9-5) — The N-20PA display is
controlled by the display control circuitry. A sensor is used to measure
ambient light. During low-light conditions, the display backlight, an
electroluminescent device, is automatically switched on.
Main PCB
Microprocessor

Figure 9-5: Display Control Block Diagram

• Printer Control Block Diagram (Figure 9-6) —Printer circuitry is divided
into two subsections: the printer interface and the printer flex circuit.
AUX PCB
Power
shutoff
circuits
(fuse;
EMI protect;
ESD protect)
Main PCB
Control
Display driver
conditioning
circuit
(generates
timing
Display driver
signals)
AUX PCB
High voltage
control circuit
(enables
+70 VDC
to display)
+5 VDC
Power
+70 VDC
supply
circuits
–5 VDC
+10 +12 VDC
VDC
SpO
2
Analog
section
(main board)
AUX PCB
(1)
(2)
70 volts
Main PCB
Microprocessor
Display drivers
AUX PCB
Display backlight
Display
Display
backlight