Sharp AR-5012 Service Manual page 81

(9) Operation circuit
a. General
The operation circuit is composed of the key matrix circuit and the dis-
play matrix circuit.
b. Key matrix circuit
Select signals SELIN 1 – 3 are sent from the CPU of the MCU to the
selector in the operation circuit.
The signals detecting OFF/ON of the key are sent to the CPU as KIN 1
– 2.
c. Display circuit
The display is controlled by sending the data signal from the CPU of
the MCU, the clock signals, and the latch signals from the ASIC to the
LED driver in the operation circuit.
∗ The basic circuitry is the same as that of Puma.
(10) I/F circuit
a. General
The I/F circuit is composed of the USB driver and the IEEE1284 driver,
and performs hard interface with the ASIC (MCU PWB).
b. USB circuit
With the USB driver, the differential signals (analog) of USB are con-
verted into digital signal, which are sent to the ASIC. In the reverse
procedure, interface between the ASIC (engine) and the host is per-
formed.
USB driver
ASIC IC401
OE, RCV, VP, VM
Suspend, VMO
VPO
prevention circuit
Noise filter
circuit
Overcurrent
protection circuit
D+
USB
connector
D -
Rush current
Inverter circuit
Rectifying/
(Flyback converter system)
smoothing
circuit
Control
circuit
AR-5012 ELECTRICAL SECTION 13 - 11
c. IEEE1284 circuit
The IEEE1284 driver is used to perform interface between the ASIC
(engine) and the host.
ASIC
(11) Carriage unit
a. General
The carriage unit is provided with the CCD PWB, the inverter PWB,
and the lamps. It scans documents and transfers AD-converted image
data to the ASIC.
b. CCD PWB
The CCD on the CCD PWB employs the color image sensor uPD8861
of 5400 pixels x 3 lines, and scans documents in the main scanning
direction in the resolution of 600dpi/US letter size.
Image data scanned by the CCD are inputted to the AFE (AD9826),
and subject to CDS, amplification, and AD-conversion. Then digital
data are outputted to the MCU PWB and to the ASIC, which performs
image process of the digital data.
c. Lamp inverter PWB
The transformer is controlled by the lamp control signal from the MCU
PWB. The transformer output controls lighting of the cool cathode ray
tube.
B. DC power circuit
The DC power circuit directly rectifies the AC power and performs
switching-conversion with the DC/DC converter circuit, and rectifies
and smoothes again to generate a DC voltage.
The constant voltage control circuit is of +5VEN. +24V and +12V are of
the non-control system by winding from the +5VEN winding. As shown
in fig (1), +24V, +12V, and +5V are provided with the ON/OFF function
by external signals. +3.3V is outputted from +5VEN to the regulator IC.
Refer to the block diagram, fig (1).
Rectifying/
smoothing circuit
Rectifying/
smoothing circuit
Rectifying/
smoothing circuit
Constant-voltage
detection circuit
fig (1) Block diagram
IEEE1284
driver
IC403
(Semiconductor switch)
+12V regulator IC
(with ON/OFF function)
(Semiconductor switch)
+3.3V
regulator IC
Centronics
connector