Epson 4001968 - page 43

STYLUS 800 Service Manual Operating Principles

2.3.2.6

Printhead

Drive Circuit

The

printhead

drive circuit for this printer is composed of the following two parts:

❑

Common drive circuit (trapezoidal drive pulse generation)

■

Head drive circuit (nozzle control built on the

printhead)

The 64-bit thermal head driver

SED5620D

in the head drive circuit on the

printhead

is used as a

nozzle selector to drive the

printhead

nozzles selectively. Print data is converted into serial data by

gate array E05A85EB

(IC3)

and is output from port S1 (pin 63) to the head drive circuit on the

printhead

as data for each nozzle. Then, head driver

SED5620D

latches the head data when gate

array

E05A85BE

outputs the

LAT

signal, and the latched data becomes 48-bit parallel data, with one

bit corresponding to each nozzle of the

printhead.

When data transfer and nozzle selection is

complete, gate array

E05A85BE

outputs the common drive pulse

PWC

(charge pulse) and

PWD

(discharge pulse) to the common drive circuit. The co

mmon drive circuit then generates the

trapezoidal pulse and applies it to the

printhad

as a common drive pulse. After this, the

nozzle

selected by the head data is activated to inject ink by energizing the MLP element drive with the

applied trapezoidal drive pulse.

JAIL

GND .--------: ------- j-----------------------

--’-------------------------

Pwc

;

(IC3)

HCLK

‘5

LAT

‘4

HCLK

;

LAT

+5V4

‘2TH

I I

HEAD-2

CPU

AN1

(CN3)

(lCl)

Figure 2-19. Printhead Drive Circuit Block Diagram

Rev.

2-17