Printhead substrate, printhead using the substrate, head cartridge including the printhead, method of driving the printhead, and printing apparatus using the printhead
This invention relates to a printhead substrate capable of suppressing an increase in wiring width and an increase in the size of a substrate formed by a film forming process while increasing the number of simultaneously driven printing elements in order to improve the printing performance, a printhead using the substrate, and a printing apparatus using the printhead. The wiring lines of the substrate are formed into a common wiring line, and energy applied to a heating resistance element is prevented from deviating from a stable ink discharge range owing to the difference in the number of simultaneously driven heating resistance elements. For this purpose, a driving element is greatly downsized in comparison with a conventional one, and the operation region of a MOS transistor is shifted from the non-saturation region to the saturation region.
1. A printhead substrate having a plurality of printing elements, and driving elements, which are arranged in correspondence with the plurality of printing elements, switch and control driving of corresponding printing elements, and are formed from MOS transistors, comprising:
a common wiring line which commonly supplies power, and to which a plurality of simultaneously drivable printing elements out of the plurality of printing elements are connected;
a first pad which supplies power to said common wiring line;
a logic circuit which controls the plurality of driving elements;
a GND wiring line which corresponds to said common wiring line and is shared over a plurality of blocks; and
a second pad which connects to said GND wiring line,
wherein each of the driving elements is an element for supplying a constant current to the corresponding printing element, and
the plurality of printing elements are connected to said common wiring line such that resistance values from each of the plurality of printing elements to said common wiring line are substantially equal to each other.
2. The printhead substrate according to claim 1 , wherein
the plurality of printing elements are electrothermal transducers; and
one terminal of each of the electrothermal transducers is connected to said common wiring line, and the other terminal is connected to a drain of the MOS transistor.
3. The printhead substrate according to claim 2 , wherein the MOS transistor operates in a saturation region of a drain source current.
4. The printhead substrate according to claim 1 , wherein each printing element is substantially equivalently connected to said common wiring line.
5. The printhead substrate according to claim 1 , wherein said common wiring line is connected to the printing elements as a single wiring line without branch out.
6. The printhead substrate according to claim 1 , wherein said common wiring line is strip-like.
7. A printhead using the printhead substrate according to claim 1 .
8. A printing apparatus which prints by using the printhead according to claim 7 .
9. A printhead substrate having a plurality of printing elements, and driving elements, which are arranged in correspondence with the plurality of printing elements, switch and control driving corresponding printing elements, and are formed from MOS transistors, comprising:
a common wiring line which commonly supplies power, and to which a plurality of simultaneously drivable printing elements out of the plurality of printing elements are connected;
a first pad which supplies power to said common wiring line;
a setting circuit which sets a gate width of a MOS transistor for energizing one of the printing elements; and
a driving circuit which drives the MOS transistor having the gate width set by said setting circuit,
wherein each of the driving elements is an element for supplying a constant current to the corresponding printing element, and
the plurality of printing elements are connected to said common wiring line such that resistance values from each of the plurality of printing elements to said common wiring line are substantially equal to each other.
10. The printhead substrate according to claim 9 , further comprising a resistance having a value representative of resistance values of the printing elements,
wherein said setting circuit sets the gate width on the basis of the resistance value of said resistance.
11. The printhead substrate according to claim 9 , wherein
the MOS transistor is formed from a plurality of small MOS transistors which are connected to the printing element and have different gate widths, and
said setting circuit sets the gate width by setting the driving number of the small MOS transistors.
12. The printhead substrate according to claim 11 , wherein the driving number of the small MOS transistors is set by a sum of a current value based on the representative resistance value and saturation currents of the small MOS transistors.
13. A printhead using the printhead substrate according to claim 9 .
14. A printing apparatus which prints by using the printhead according to claim 13 .