APPENDIX D
MAXIMUM OPERATING CONDITIONS
FOR ROHM KF2008-B1 THERMAL PRINT HEAD
The following are constants given by ROHM for this style of printhead:
Maximum allowed applied power
Po max = 0.82 watts/dot
Maximum allowed applied voltage
Vset max = 26.4 volts
Resistance of internal power bus
Rcom = 0.13 ohms
Resistance of internal drivers
Ric = 22 ohms
Rlead = 30 ohms
ROHM also specifies the following table relating cycle time to the maximum allowed applied
energy per dot.
Cycle time
Eo max
2.5 msec
0.30 mj/dot
5.0 msec
0.35 mj/dot
10.0 msec
0.39 mj/dot
20.0 msec
0.40 mj/dot
For a given voltage setting, the applied power is calculated according to the following
equation:
Po=Vset x Rav/(N x Rcom + Rav + Ric + Rlead)
where the constants have been previously defined and
N is the number of dots printed simultaneously, for 100% pattern this number is 608.
Rav is the average dot resistance printed on the label on the front of the printhead.
Vset is the voltage applied.
******IMPORTANT******
Vset MUST be adjusted such that Po is not greater than 0.82 watts.
The maximum allowed strobe time (Ton max) for any given voltage setting (Vset) is calculated
as follows:
Ton max = Eo max/Po
