Sharp PC-E500 - Low Battery Detection Circuit

PC-E500
pau
(Not used.)
(Not used.)
(Not used.)
Input
7. Low battery detection circuit
The
PC-E500
is
equipped
with
the
low
battery
detection
circuit.
The
operations
of
the
circuit
are
described
below.
(Part
location
numbers
may
differ
from
those
in the
actual
circuit
diagram.)
When
input
voltage
VIN
exceeds
the
detection
voltage
VD,
the
output
of
the
voltage
detection
IC
[LBIC(MN1280)]
is
driven
from
Low
to
High.
When
VIN
falls
under
VD,
the
output
is
driven
from
High
to
Low.
~The
LBIC
(MN1280)
detects
both
the
CAU
level
and
the
STOP
level
by
dividing
the
voltage
applied
to
the
input
terminal
(2
pin)
with
Rit
and
R2
and
by
turning
on/off
R2
with
CAU
signal
of
G-A.
When
the
power
voltage
falls
under
the
CAU
level,
as
shown
in
Fig.
3,
the
BATT
symbol
lights
up.
When
the
power
voltage
falls
further
under
the
STOP
level,
the
symbol
goes
off.
For
CAU
level
detection,
the
CPU
ES
it
turned
on
(low
level)
and
the
CPU
IRQ
terminal
state
is
observed.
(if
the
IRQ
is
at
Low
level,
the
symbol
lights
up.)
When
the
CAU
level
is
detected,
the
CPU
ES
terminal
is
turned
off
(high
impedance).
(When
the
CPU
E3
terminal
is
turned
off,
resistor
division
is
not
performed
and
the
voltage
at
LBIC
2
pin
increases,
driving
the
output
from
Low
to
High.)
The
CPU
IRQ
terminal
state
is
checked
again
to
detect
the
STOP
level
SiO PAK (Not used.)
Signal description
ROM ecard chip select signa! (active high)
Chip select signal for display chip (Active high)
Internal ROM chip enable signal
RAM card chip enable signal
internal RAM chip enable signal
Output | Key strobe signal
2
Output
Input SIO RD (Receive data)
Output SIO SD (Send data)
Input
Input CE-140F data input terminal
input
Input
Output 11 pin DIN
Output 11 pin DOUT
Output 11 pin 102
Output 11 pin 101
Input 11 pin ACK
Output 11 pin BUSY
- (Not used.)
Output Display power (converter) control signal
Output Low battery voltage control signal
Input SIO CS (Opponent side send enable)
Input SIO CD (Opponent side send request)
After
the
STOP
level
is
detected,
the
ON
key
and
the
RESET
key
be-
come ineffective.
10000 ~ 1FFFF
00000 ~ O3FFF, 08000 ~ OBFFF
C0000 ~ FFFFF
40000 ~ 7FFFF
80000 ~ BFFFF
P-ch open output
P-ch open dutput
P-ch open output
P-ch open output
P-ch open output
CPU IRQ
GPU E3
N-ch open
Fig. 3
Voltage detection IC
operational description
Low battery detection circuit check
CAU level VCC — GND: 4.2V to 4.6V
STOP level VCC - GND: 3.8V to 4.2V