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2.5 THERMAL HEAD
2.5.1 Structure of the Thermal Head
As Figure 2-7 shows, the LTP3445 thermal head consists of 832 heat elements, heat element drivers and
preline history controllers. The preline history controller allows the preheat pulse to be applied to
nonactivated elements on the preceding dot line before the main heat pulse.
Serial print data input from the HDAT terminal is transferred to the shift register synchronously with the
HCLK signal. When the print data is input at the High level of the CTRL terminal, only nonactivated dots
on the preceding dot line are automatically transferred to the shift register as print data, then stored in the
latch register at the timing of the LATCH signal. Next, when the print data is input at the Low level of the
CTRL terminal, main heat pulse data is transferred to the shift register.
832 dots are divided into 13 blocks, namely -- 1 block consists of 64 dots, allowing for individually-divided
printing. At the “High” level of the CTRL terminal, the block to be activated inputs 13-bit data which is
selected synchronously with the HCLK signal to the BDAT terminal in serial. 13 bits correspond to the
respective block. Only the block corresponding to ON bit is activated. Table 2-6 shows Blocks and
Activated Heat Elements.
Turning ON the head activation signal (DST) activates heat elements in accordance with the print data
stored in the latch register. Apply the preheat pulse. Next, by inputting the LATCH signal, the main heat
data is stored in the latch register. Turn the DST ON and apply the main heat pulse.
As for remaining blocks, follow the same steps shown above. Select an appropriate block and apply the
preheat pulse and main heat pulse.
Printing without preline history control is possible only by leaving the CTRL terminal “Low”.
For more detailed drive method, refer to Chapter 4, “DRIVE METHOD”.
Summary of Contents for LTP3445
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