CS2516
Applications Formulae and Typical Values
Program and Standby Currents:
I
P
=
Cycle Timer Period:
T
t
=
V
CC
=
R
P
9V
9.1m�½
Å 1µA
Standby Current = 4I
P
= 4µA (typ.)
V
T
C
T
7C
T
7 x 4.7µF
=
=
Å 33sec.,
I
P
1µA
1µA
where V
t
= Upper Charge Threshold - Lower Charge Threshold (7V typ.)
Test Pulse Width:
T
p
= R
d
C
T
x ln(V
P
) Å 242C
T
Å 242 x 4.7µF Å 1.14ms
where R
d
is the dynamic cycle timer discharge impedance (440�½ typ.)
and V
P
=
Upper Charge Threshold
Lower Discharge Threshold
[1n(V
P
) = 0.55 typ.]
Pulse Stretcher: Delay Time:
T
D
=
V
d
C
PW
2.5C
PW
2.5 x 0.1µF
=
=
Å 1ms
250µA
I
src
250µA
where V
d
= Schmitt Trigger Upper Threshold (2.5V typ.)
and I
src
= Typical source current at the PW pin at the nominal low battery sense threshold of 6.7V.
Pulse Width: T
p
= C
PW
R
PW
ln(V
S
) Å 0.51 x 0.1µF x 10m�½ Å 510ms.
and V
S
=
Schmitt Trigger Upper Threshold
Schmitt Trigger Hysteresis
Applications Information
The value of R
p
affects standby current, operating current,
and the test cycle period. The recommended value is
(V+/1µA) where V+ is the fresh battery voltage. Higher
values of R
p
are not recommended. Minimum recom-
mended value is (V+/10µA) which will increase both the
standby and operating currents by 10X and reduce the test
cycle period by the same factor; the test pulse width will
be unaffected.
The value of C
t
affects both the test cycle period and the
test pulse width. Of critical importance is the selection of a
low leakage type capacitor; if leakage current exceeds the
cycle timer charge current, the timer will not operate.
The pulse stretcher components R
PW
and C
PW
should be
selected such that the delay timer to charge C
PW
is shorter
than the test pulse width programmed by C
t
to guarantee
operation of the Output. The output is an open-collector
transistor which may be used to drive an indicator device
directly or to interface to logic family devices.
The SENSE input typical 8.5k�½ input impedance appears
only during the test pulse; otherwise the SENSE input is in
a high impedance state. The effective low battery thresh-
old voltage can be modified (increased only) by means of a
voltage divider placed across the load resistor. This tech-
nique can also be used to effectively reduce the threshold
tolerance band.
[ln(V
S
) = 0.51 typ.]
Typical Application Circuit
R
p
9.1MW
R
p
V
CC
V
CC
C
pw
SENSE
C
T
PW
0.1mF
R
pw
CS2516
+
C
T
OUT
10MW
510W
4.7mF
COM
Load Switch
220W
+
9V
4
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
