Circuit Description - Sharp MD-MT20 Service Manual

MD-MT20/20C/20W
IC401 RH-iX0298AWZZ: System Microcomputer (IX0298AW) (3/3)
System LSI expansion output port (6th generation: LR37811)
Terminal Name Input/Output
Pin No. Port Name
52 EXPORT0 LDCNT1
53 EXPORT1 LDCNT2
54 EXPORT2 —
55 EXPORT3 EMPH1
56 EXPORT4 DCNT
57 EXPORT5 OPTCNT
58 EXPORT6 DAPON
59 EXPORT7 ADPON
*1: List of TEST port settings
TEST1 TEST0
H H Normal mode
H L No adjustment mode
L H Test mode
L L (Settings prohibited)
Charging control works as shown below.
Charging is performed in the following three modes.
Initial charging -> Main charging
The details are shown below.
The current value is measured by voltage on both ends of R250/R251.
Initial charging
The charging current is approx. 250 mA. The initial charging time varies depending on the battery condition. The charging time may
be more than five minutes, depending on the initial battery condition. If the battery voltage is below 2.0 V (or over 3.75 V) after two
minutes, the charging mode is cancelled. When the battery voltage is over 2.0 V and less than 3.75 V after five minutes, the main
charging mode is selected.
Main charging
The charging current is approx. 375 mA. The main charging time varies depending on the battery condition.
<Main charging stop mode>
When the full-charge check is performed, the output of pin 51 is pulled H and the voltage is measured at five minute intervals (eight
separate voltage measurements should be made to get a mean voltage value for consideration). The voltage value is read 500 msec
after the output of pin 51 (battery voltage detection gain select output) is pulled H.
The current reading is compared with the reading taken 30 minutes before and one of three judgements is given: Same, Higher or
Lower.
The voltage drop is detected, and the charging is stopped.
When battery voltage is over 2.8 V, a full-charge check will be performed (when it is below 2.8 V, the full-charge check will not be
conducted).
When the battery voltage is not over 2.8 V, the initial charging mode is not changed to the main charging mode.
It may be more than five minutes before the battery voltage exceeds 2.8 V.
(The initial charging time varies depending on the battery condition.)
Supplementary charging
The supplementary charging mode (charging current: 250 A) will be engaged using the following specifications, depending on the
main charging mode.
After the main charging is completed, the battery is charged for about two hours at a current of 250 mA, and then the charging mode
is cancelled.
Output
Output
Output
Output
Output
Output
Output
Output
*2: List of EMPH port settings
EMPH1
Details
H
H
L
L

CIRCUIT DESCRIPTION

Supplementary charging -> Finish
Function
Recording head raising-lowering control output 1
Recording head raising-lowering control output 2
Not used.
Audio emphasis control output 1
Mechanism driver enable output
Optical digital input circuit control
D/A converter operation control output
A/D converter operation control output
EMPH0
Details
H fs=32K: 'ON'
L fs=48K: 'ON'
H OFF
L fs=44.1K: 'ON'
– 42 –
Remarks
See the separate table *3.
See the separate table *3.
(Open)
See the separate table *2.
'H': Driver operation ON
'H': Circuit operation ON
'H': Operation ON
'H': Operation ON
*3: List of LDCNT port settings
LDCNT1 LDCNT0
H H Brake
H L Drive UP
L H Drive DOWN
L L Output OFF
Details