2-27
2.7 HEAD-UP DETECTOR
LTP3445 has a built-in head-up detector to detect whether the head is up or down. This detector is a
mechanical switch which is designed to close when the head is in the down position (printing state) and to
open when in the up position.
The external circuit should be designed so that it detects the output from the head-up detector and does
not activate the thermal head when the head is in the up position. Otherwise, the thermal head may be
damaged or the life of the head may be shortened significantly.
2.7.1 General Specifications
Maximum rating:
5 V DC, 1 mA
Contact resistance:
70 m
=
Ω
maximum
2.7.2 Sample External Circuit
Note that there is a time lag between the time when the thermal head stays completely up or down and
when the head-up detector starts to operate.
Always use the capacitor shown in Figure 2-12 to prevent the switch from malfunctioning as a result of
chattering.
The mechanical switch is closed when the head is in the down position.
Figure 2-12 Sample External Circuit for the Head-Up Detector
MECHANICAL
SWITCH
GND
TO CPU PORT
V
cc
(5 V)
R=10 k
Ω
Ω
Ω
Ω
HS
GND
C=0.1
µµµµ
F
PRINTER
Содержание LTP3445
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