Mindray Passport 5-Lead, Service Manual

Page: 258 / 544

Block Diagrams Theory of Operation
2 - 56 0070-00-0420 Passport 5-Lead, 5L, LT, XG Service Manual
FIGURE 2-24 Planar EL Panel Board Block Diagram
EL Panel Circuits
The EL panel board circuit consists of signal through lines, data line buffers, and a LED drive
circuit. The display is a 30fL pixel, electroluminescent flat panel. It has a display matrix of
640 by 200 addressable pixels. The data lines and supply voltages are connected to the
EL’s DC/DC converter through J74. The supply voltages (+12V and +5V) come from the
microprocessor board via J71 on the panel board. The supply voltages are then converted
to the voltages used by the EL panel.
LED Indicator Circuits
The alarm indicator D1 is implemented by a high intensity red LED, HP type HLMP K101 or
equivalent. It is driven by the FET Q1, type 2N7000 which is controlled by the signal LED0
form the CPU board. Power On is indicated by the green LED HP type HLMP 1790 or
equivalent. It is driven directly from Vcc through the current limiting resistor R6.
Keyboard Interconnections
The four input lines K10 through K13 and the eight output lines KD0 through KD7 provide the
interconnection between the CPU board and the 8 by 4 keyboard matrix.
Speaker Interconnections
The speaker signals for alarm and beep tone are interconnected between the CPU board and
the loudspeaker.
Kl/KD
Buffers
LED Drivers
Keyboard
Interface
J72-12 Pin
PWR ON
ALARM
DC/DC Converter
J74-16 Pin
4 Control/Data Lines
12 Keyboard I/O Lines
J7 5
Speaker
CPU Interface
J71-40 Pin
EL
+5V
+12V
GND P
GND D
DO
SPK
KI/KD
EL C/D
+5V
+12V
GND P