CS2516 Datasheet, PDF (4/6 Pages) Cherry Semiconductor Corporation – Pulse-Load Battery Monitor

Applications Formulae and Typical Values
Program and Standby Currents:
I_P
=
V_CC
R_P
=
9V
9.1m½
Å 1µA Standby Current = 4I_P = 4µA (typ.)
Cycle Timer Period:
T_t
=
V_TC_T
I_P
=
7C_T
1µA
= ^{7 x 4.7µF}
1µA
Å 33sec.,
where V_t = Upper Charge Threshold - Lower Charge Threshold (7V typ.)
Test Pulse Width: T_p = R_dC_T x ln(V_P) Å 242C_TÅ 242 x 4.7µF Å 1.14ms
where R_d is the dynamic cycle timer discharge impedance (440½ typ.)
Upper Charge Threshold
and V_P = _{Lower Discharge Threshold}
[1n(V_P) = 0.55 typ.]
Pulse Stretcher: Delay Time: T_D =
V_dC_{PW =} 2.5C_{PW =} 2.5 x 0.1µF _{Å 1ms}
I_src
250µA
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_PWR_PW ln(V_S) Å 0.51 x 0.1µF x 10m½ Å 510ms.
and V_S =
Schmitt Trigger Upper Threshold
Schmitt Trigger Hysteresis
[ln(V_S) = 0.51 typ.]
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 8.5k½ 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.
Typical Application Circuit
R_p
9.1MW
C_T+
4.7mF
R_p
V_CC
SENSE
PW
CS2516
C_T
OUT
COM
Load Switch
V_CC
C_pw
0.1mF
R_pw
10MW
510W
220W
4
+
9V