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1054417, V
ER
. 01
P
AGE
22
Alice
®
PDx
TM
Service & Technical Reference Manual
LCD D
RIVER
The microcontroller communicates with the LCD via I2C port 2. The 3.3 volt logic levels of the microcontroller
are translated by U2 to the 5 volt levels as required by the off board LCD. The LCD contains its own PCA8576
driver on the LCD glass.
B
ATTERY
PCA
B
ATTERIES
Power for the Alice PDx is provided by three user-replaceable “AA” size cells which are mounted by means of
spring clips to the battery board. While the preferred cell chemistry is either alkaline or NiMH, it is recognized
that chemistries other than the preferred ones may be used. While these alternate chemistries may not provide
ideal performance, they should not cause damage to the Alice PDx or the batteries and must not cause a
hazardous condition to occur.
O
VERCURRENT
P
ROTECTION
Overcurrent protection is provided by positive temperature coefficient thermistor F1.
R
EVERSE
P
OLARITY
P
ROTECTION
Protection of the device from the application of reverse polarity is provided by P-channel MOSFET Q1. An RC
network at the gate of Q1 provides a slow turn-on of power to the VBATT bus. This slow turn-on feature limits
the charging current to capacitors on the input of the DC to DC converters (digital board) enough to prevent
damage to MOSFET Q1.
SD C
ARD
The battery board contains the socket for the SD card.
I
NDICATOR
LED
The battery board contains a bi-color (yellow/green) LED as part of the user interface. Inverters U1 and U2
provide drive current to the LEDs, as commanded by the microcontroller.
NOTE
Refer to Alice PDx Digital Board Schematic sheet 5 located in the Schematics section beginning on
page 53.
NOTE
Refer to Alice PDx Battery Board Schematic sheet 1 located in the Schematics section beginning on
page 53.
Содержание Alice PDx
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