LTPH245 datasheet(40/64 Pages) SII

40 / 64 page

3-27

3.6.10

Detecting Abnormal Temperatures of the Thermal Head

To protect the thermal head and to ensure personal safety, abnormal thermal head temperatures must

be detected by both hardware and software as follows:

Detecting abnormal temperatures by software

Design software that will deactivate the heat elements if the thermal head thermistor (TH)

detects a temperature 80

°C or higher (thermistor resistance RTH ≤ 2.48 kΩ), and reactivate the

heat elements when a temperature of 60

°C or lower (RTH ≥ 4.46 kΩ) is detected. If the thermal

head continues to be activated at a temperature higher than 80

°C, the life of the thermal head

may be shortened significantly.

Detecting abnormal temperatures by hardware

If the control unit (CPU) malfunctions, the software for detecting abnormal temperatures may not

function properly, resulting in overheating of the thermal head. Overheating of the thermal head

may cause damage to the thermal head or injury.

Always use hardware in conjunction with software for detecting abnormal temperatures to

ensure personal safety.

(If the control unit malfunctions, it may be impossible to prevent

damage to the thermal head even if a detection of abnormal temperature is detected by

hardware.)

Using a window comparator circuit or similar detector, design hardware that detects the

following abnormal conditions:

(a) Overheating of the thermal head (approximately 100

°C or higher (RTH ≤ 1.47 kΩ)).

(b) Faulty thermistor connection (the thermistor may be open or short-circuited).

If (a) and (b) are detected, immediately deactivate the heat elements.

Reactivate the heat

elements after the temperature of the thermal head has returned to normal.

LTPH245 Datasheet(PDF) 40 Page - Seiko Instruments Inc