ACT5880
Rev 2, 03-Sep-13
RB, are used to condition the string to have the
desired ratios at the wanted hot threshold
temperature and cold threshold temperature.
USB circuit, the pull-up of charge state LED, the
pull-up for BATID input, the pull-up for ACIN input
and the pull-up for TH input. It may not be allowed
to apply higher voltage on the CHGIN considering
those other connections.
Figure 18:
The Battery Thermal Condition Circuit.
Typical Application Consideration
CHGIN
The charger circuit is well compensated, can be
used to charge various capacities cells without
modifying the input and output decoupling caps,
which is 6.8μF~22μF for the input and 4.7μ~10μF
for the output.
0. 748
RA
=A·R25
Battery
Assembly
ACT5880
TH
0. 349
RB =B·R25
NTC
=r·R25
Autonomic and Slave Charge
GA
(Ground )
The charge state machine in the ACT5880 is a
complete autonomy. It senses the condition
parameters, manages charge profile and indicates
charge status without any foreign involvement.
The normal temperature range cells typically work
in -20°C to 40°C while the extended range is -20°C
to 60°C. Giving the a NTC thermistor with 25°C
characteristic resistance of R25, the resistance ratio
at hot threshold temperature is rH and at cold
threshold temperature is rC, the proportion factor A
and B for having the 2 precise ratios 0.748 and
0.349 are found as:
The charger wakes up the host system, and calls
for host system involvement if it is configured so.
With this mechanism, the ACT5880 could work as a
slave charger with host system involvement on
demand.
Li+ Poly Cell and Li+ Cell Charge
The scheme and the default setting are optimized
for single cell Li+ poly charging. Li+ poly cells with
4.2V charge termination voltage, which are the
most common battery types in phone designs.
A=0.411·(rC−rH)
B=0.220·rC−1.22·rH
It is necessary to verify how much power is desired
to bias the selected NTC thermister, to assure no
excessive self heating generated.
In case of using 18650 cylindrical cell, which is
typically with 4.1V charge termination voltage (the
termination voltage is anode material dependent, is
specified for a battery model), applying 4.2V on it
does not cause instant damage. It is possible to
start with 4.2V battery regulation voltage and then
program it to 4.1V later, but this is not rational for
safe charging. Contact factory for ordering parts
with 4.1V default.
The resistance ratio r is the ratio of the resistance at
a temperature to the resistance at 25°C. This ratio
is found from the NTC specification in a table or a
curve plot.
Reverse Block
The ACT5880 has a reverse block circuit in the
charge path. Whenever the VCHGIN is less than
NiMH cells charge
V
VBAT, as low as to 0V, the reverse block circuit
Though the charge scheme is not optimized for
charging NiMH cells, its current limit and voltage
limit, auto-restart features make the ACT5880
charger a practically applicable charger in fix
wireless terminal applications for 3 NiMH cells
charging with its 4.2V to 4.4V battery regulation
voltages. In this kind of applications, the cells are
floating charged at 1.4V to 1.47V per cell, which is
in the good range for floating and uses the most
part of the battery capability. Figure 19 shows the
typical curves for NiMH battery.
prevents the reverse leakage from VBAT to CHGIN
and the state machine jumps into Sleep State. This
reverse block circuit does not work in LDO mode
operation.
Input Over Voltage
The CHGIN allows applying continuous 12V and
momentary 14V on it. When the voltage applied on
CHGIN is greater than the over voltage threshold,
the state machine jumps into Sleep State and
charging stops.
As in the real application circuitry often has other
connection to the CHGIN, such as the VBUS of
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