Sharp PC-E500S

7. Low battery detection circuit
This model is equipped with the low battery detection circuit, the
operations of which are described below. (Location Nos. of the parts
are different from the actual ones.)
As
shown
in
the
figure
below,
the
output
of
the
voltage
detecting
IC
[LBIC
(RH5VA39A)]
turns
HIGH
when
input
voltage
VIN
exceeds
detecting
voltage
VD.
When,
on the
contrary,
VIN
falls
below
VD,
the
output
turns
LOW.
The LBIC (RH5VA39A) detects two levels; the CAU level and the
STOP level. For that reason, a voltage applied to the input pin (2 pin)
is
divided
by
R1
and
R2,
and
R2
is
turned
on/off
by
the
CAU
signal
of
G.A.
When the power voltage falls below the CAU level, as shown in Fig.
3,
the
BATT
symbol
lights
up.
When
it
falls
further
below
the
STOP
level, the BATT symbol goes off.
To detect the CAU level, the CPU E3 is turned on (LOW) and the
CPU
IRQ
pin
state
is
checked.
(If
the
IRQ
pin
is
at
LOW,
the
symbol
lights up.) :
When
the
CAU
level
is
detected,
the
CAU
pin
is
turned
off
(HIGH).
(When
the
CAU
E3
is
turned
off,
resistance
is
not
divided,
rising
the
potential
at
BIC
2
pin
and
turning
the
output
from
LOW
to
HIGH.)
Then
the
CPU
IRQ
pin
is
checked
again
to
check
the
STOP
level.
After
detecting
the
STOP
level,
ON
key
and
RESET
key
are
made
invalid.
7
VCC VCC [Fig. 1]
Ag no ePuL
i {
res LB A
CPU E3__ hoicel | IRQ
B
(V) TIN
oo
Power voltage (V)
\.
Voltage
detection
IC
operation
Symbol!
lights
up.
[Fig. 2] [Fig. 3]
Low battery detection circuit check
CAU level VCC-GND: 4.2V - 4.6V
STOP level VCC-GND: 3.8V - 4.2V
8. Current consumption check
Power source: 11-pin connector, +5V - OV applied to VCC (2 pin) -
GND (3 pin)
Current:
At
ON
(BASIC
mode
with
">"
displayed),
3.29
mA
or
less.
At
OFF
(Power
OFF),
22.8
uA
or
less.
Reference
PC-E500S5
[__[eseration | display |
DC-DC =
| converter 3
pvoo | 075m A
TC4S81F
| TC3WO1F
§-1.
Current
consumption
and
low
battery
voltage
detection
Ammeter
Turn on the main DC
| = _ power (+6.3V 40.1 V). a
Ee While pressing ON key,
press RESET key.
* Press Y key to initialize
the internal RAM.
Press PF1 key to go into
the BASIC mode.
*
Check
">"
display
and
|
check
the
current
value.
|
(The
current
should
be
|
3.77
mA
or
less.)
Set
the
DC
power
to+4.1)*
Check
that
the
BATT
|
+0.05V.
symbol
lights
up.
:
|
4
|°
Set
the
DC
power
to,*
Check
that
the
display
is
+3.7V+ 0.1V. out
4
i
eee ne ewww we ee eee ew eee eee
5
Return
the
DC
power
to
|
*
Check
that
the
display
is
|
+6.3V
+
O.1V.
|
out
and
check
—
the
|
:
current.
(The
—
current
|
|
|
should
be
22.8nA.)
1
6
|
*
Disconnect
the
1i-pin
|
|
connector.
|
|
the 11-pin connector with |
a 3.9KQ resistor for 6 |
sec. |
Note:
if
there
are
any
data
or
program,
save
them
in
advance
to
this
check.