3-16
3.4 THERMAL HEAD
The thermal head consists of heat elements and a thermal head driver that drives and controls the heat
elements. The printing data input the DI terminal is “High” at printing and “Low” at non printing.
The data from the DI terminal is transferred to the shift register at the rising edge of the CLK signal.
The data is stored into the latch register by making LAT signal "Low" after one line data is transferred. The
heat elements are activated by making DST signal "Low" in accordance with the stored print data.
In the LTPD247, a division printing by 3 blocks is available. Each block has 144 dots heat elements.
In the LTPD347 a division printing by 144 dots in 4 block each are available. The divided printing is effective
for a high print ratio printing because the peak current can be cut down with the reduction of the average print
speed.
3.4.1 Structure of the Thermal Head
Figure 3-7 shows the thermal head block diagram when driving the LTPD247.
Table 3-7 and Table 3-8 show the relationship between DST blocks and activated heating elements.
Block3
Block2
Block1
････
････
････
Output driver
Latch resister
Shift register
Heat elements
DI
CLK
LAT
DST3
DST2
DST1
TH
TH
V
dd
GND
V
P
Thermistor
DOT4
32
DOT2
89
D
OT288
DOT1
45
DOT1
44
DO
T1
Figure 3-7 Thermal Head Block Diagram(LTPD247)