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Model
5315A/
B
Service
regulator,
leaving
only the
10 rnA regulator. The
battery vo
ltage
begin
~
to
drop,
and,
at
a
~e
t
lower
limit, the comparator reactivat
es the
500 rnA
regulator.
The du
ty
cycle
of the 500 rnA
regulator
s
hift~
proportiona
lly,
as
the
battery charges up;
the
higher
the
c harge leve l,
the
longer
the
"off"
cycle,
until at full
charge,
it
remains off
and
only
the mA
regulator
runs, providing a
trick le
charge
to
maintain
the
battery
charge level.
The
charge
ligh
t
an
nunciato
r
circuit
monitor~
the
output of the
charge
comparator,
displaying
the
charg
ing
duty
cycle via
a front pane
l
LED.
8-65.
BaUery Discharge Cycle
8-66.
The
posi
tive
battery
voltage,
during
discharge,
i
~
~wilched
through the
STBY
I
ON
switch
10
the
posit
ive
regu
lators on the mothe
rboard
assembly.
In
addition, this
switched
battety
voltage is
fed back to
the
charger
assembly, where
it
i~
input
to a
DC-to-DC
converte
r,
the 2.5V
refer
e nce
regu
lator
and
the discharge ci
rcuitry. The
DC-to-DC converter
basically c hanges
the
polarity,
providing
a
rnin
u
~
voltage,
which
is
output
to
the
negative
regulator
on the
moth
e r-
board
.
The
switched
battery
vo ltage
also
drives
the
2.5V
refe re
nce
regulator.
which
provides
a
refer
e nce
level for the
low
battery
detector
and
drives the
d ischa
rge
annunciator
circuit.
The
discha rge
light on the front
panel
is on
continuously under bauery
operat
ion.
The
low batte ry
detector
mon
itors the
switched
battery voltage.
If
the
battery
discharges to a
critica lly
low
level,
the
low battery detector
will disable the
cou nter,
via
the
shut-down
li
ne,
and
blink
the
discharge
annunciator
slowly.
This
places
the
minimal
c
urrent drain
on the
bauery, however
the
battery
must
be recharged
as
soon as
possi ble
or complete discharge
will
result.
8-67.
Idle
Cycle
8-68.
Under
normal
AC
operation,
the
10 mA
regulator
proyides a
trickle charge
to
ma
intai
n
battery
charge
level;
the
500 mA
regulator is d isabled and both annunciators
normally
are
out.
8-69.
BaUery Annunciators
8-70. The
Model
S315A
(only
)
counter
display includes
two
battery status
annu
nciators;
DISCHG and
CHG.
These lites are
active
on ly
when Battery-Pack
Optio
n 002
is
installed
. The
DISCHG
lit indicates
that the
instrument
is operating unde
r
battery
power. Should the
battery
cha
rge level drop
to
less than 20% of full charge,
the
counte
r will be
disabled by
Auto
Shut-Off
and the DISCHG
lit
e
wil
l
flash,
indicatin
g
charging
is
mandatory. The
CHG
lite
indicates one of
three states
of
charge, and
is
act
ive only
during the
charge cycle.
The
c harge cycle
is performed
in the
STBY
mode
only
(Le.,
POWER
switch
to
STBY and instrument
connected to
power
so urce).
The
three
states ind
icated
are as
follows:
CHG
lITE
LEVEL
OF
CHARGE
OFF
.
.............
....
.
..
....
l
OW
-
Continuous
Cha rge
flASHI
NG ...
.
.. _ .•.
.
........
MEDIUM
-
Cycling Charge
O
N ......
..
..
..
,
..............
.
..
.
HIGH
-
Trick le
Cha rge
NOTE
If
the
chalge
cycle
b
initia
ted
while a
su bsta ntial
level
of
cha
rge
still
re mai ns,
the operation
of the
CHG
lite may
be temporarily
affected
. However,
this
condi tion
will
correct itself.
8-71.
A6 Charger
Assembly Circuit Theory
8-72.
Un regu
lated
dc
from the
motherboard power
supply
is
input
to
the A6assembly
on
pin
1,
whe re
it
is
routed
to
the 10
mA regulato r,
the
500
rnA
regu
lator,
and
the
2.S-volt reference regu-
lator.
The
10 mA
regul ator consists
of Q3,
Q4,
R3,
and
R6.
The
500
rnA regulator
consists
of
U2(C).
Ql,
Q2,
and
associated
circuitry.
CR1
isolates
the chargi
ng circuits from
the battery voltage
during
dc operation. CR7 is
a
solid
state
BATIERY
/
POWER
switch
which
detects the presence of
th
e
ac
line
vo ltage.
8-11
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