Printhead Driver Circuit - Epson Stylus Photo 895 Service Manual

EPSON Stylus PHOTO 895/785EPX

2.2.2.2 Printhead Driver Circuit

The printhead driver circuit consists of the following two components:
Common driver IC (IC12:E09A14RA) directly attached to the C408 MAIN
board.
Nozzle selector IC on the head board.
The common driver (IC12:E09A14RA) generates a reference drive waveform
according to the output signals from the C408 MAIN board. The reference drive
waveform is amplified by the transistors Q2 and Q3 and then transferred to the nozzle
selector IC on the head board. Print data is converted to serial data by the CPU (IC2)
and then sent to the nozzle selector IC on the head board. Based on the serial data, the
nozzle selector IC determines the nozzles to be actuated. The selected nozzles are
driven by the drive waveforms produced by the common driver. See Figure 2-20.
"Printhead Driver Circuit" for the printhead driver circuit block diagram.
Head common driver circuit
The reference head drive waveform is produced in the common driver
(IC12:E09A12RA) based on the following 12 signal lines output from the CPU
(IC12); A0-A4, CLK1, CLK2, RST, FLOOR, DATA, DCLK, and E.
By the DATA signal output from the CPU (IC9), the original data for the head
drive waveform is written in the memory in the IC12. The addresses for the written
data are determined by the A0 - A4 signals, and, of among, data used to determine
the waveform angles is selected. Then, setting the selected data, producing
trapezoid waveform value, and canceling the data are performed by the rising
edges of the CLK1 and CLK2 signals.
Head nozzle selector circuit
Printing data is converted into serial data by the CPU (IC2). Then the converted
data is allocated to the six rows, the number of the head nozzle rows, to be
transferred to the nozzle selector through the six signal lines (HS01 to HS06). Data
transmission from the CPU (IC2) to the nozzle selector synchronizes with the LAT
signal and SCK clock signal. Referring to the transferred data, nozzles to be
activated are selected, and the PZTs of the selected nozzles are driven by the drive
waveform output from the head common driver.
Operating Principles
HWA0
HWA1
HWA2
HWA3
HWA4
HWCLK
HWCLK
HWFLR
HWRST
HWSDA
HWSCL
HWSLA
IC2 CPU
E01A22CA
HCH
HLAT
CRAI0
CRAI1
SWC0
SWC1
HSO1
HSO2
HSO3
HSO4
HSO5
HSO6
HSOCM
HNCHG
HSOCLK
ANO
Electrical Circuit Operating Principles
F1
A0 VCC
COM
A1 NPNB
COM
A2 FB
COM
A3 PNPB
COM
A4
VHV
CLK1
CN8 VHV
CLK2
FLOOR
RST CH
DATA LAT
DCLK ENA
E ENB
IC12
Common
Driver IC
Nozzle Selector
COB
COA
SI1
SI2
SI3
SI4
SI5
CN9
SI6
SP
NCHG
SCK
THM
Figure 2-20. Printhead Driver Circuit
Revision A
Head Drive
IC
Pulse
49