fs3861 Fortune Semiconductor Corporation, fs3861 Datasheet - Page 11

• Manufacturer Part Number: fs3861
• Description: Intelligent Charger Management Controller
• Manufacturer: Fortune Semiconductor Corporation

Sometimes another additional check-up procedure follows the termination of the C-V stage to assure the battery in
proper waiting stage for operation. That is to have the battery stay idle from its charge termination at full voltage of
4.20v (or 4.1v, depending on the battery’s manufacturer’s parameters). Then the battery stays in for additional 10
(or 15, also an adjustable parameter) minutes, and then its voltage is examined to assure the terminal voltage
won’t be decreased to lower than 4.05v (or 3.95v if the situation prevails), then the battery is also determined as a
defective one without reliable performance since it could be losing more than 0.15v within a short period of just 10
(or 15) minutes. These check-up procedures are optional.
In brief summary, the typical Li+ battery charger’s procedures could be summarized in the following few steps:
pre-charge conditioning, constant-current (C-C), constant voltage (C-V) stage, charge termination and monitor to
re-charge, etc. There might have some individual charge’s current- or voltage-control schemes within the
designated step to perform.
Fortune Semiconductor Corp.
˙Pre-charge conditioning (or called trickle-mode charge, as the Phase-0 stage): where the
˙Constant current charge (as Phase-1, referred as C-C stage): where the programmable constant
˙Constant voltage charge (shown as Phase-2, referred as C-V stage): using the regulated voltage
˙Maintenance re-charge (shown as Phase-3 stage): can be called Post-charge stage, which is to
The typical Li+ charge steps are mainly four stages to conduct:
low-voltage discharged battery typical lower than 3.0v (or 2.8v, depending on how the battery’s
parameters are set) gets wake-up by applying typical 1/10 of full-rate charge current (a small
amount of selectable charge current, also called trickle current, such as 85mA of 850mA charge
current ) until reaching the threshold voltage 3.0v. If the trickle current has been applied to the
battery for more than 30 minutes by timer’s measurement and not reaching the required 3.0v, it
could be detected as bad battery without continuing to the next step of charge operations.
current ranging from typical 250mA to 1,050mA is applied to the battery, until the battery voltage
reaches to the full-level at 4.2v or similar value such as 4.1v or even 4.0v. Some applications require
the constant current charge at USB current of 500mA when its power line at 5v is applied, and such
charge stage can be implemented with selection of the current regulation at 500mA by setting the
corresponding C-C reference bit and current select values at the specified control registers, as
explained in details descriptions in later section.
at 4.2v reached at the constant current charge stage until the termination condition is met at the final
low termination top-off current at smaller amount (such as 100mA which can be programmable to
select), and then charges to the full capacity when termination occurs. Selections of the C-V
charge’s voltage level can be made with corresponding C-V enable and voltage select values at the
individual specified control registers.
resume charges to the battery when the battery’s voltage drops is more than 0.1v (i.e. The battery
terminal voltage becomes 4.10v or less from its full voltage at 4.20v) as a result of the internal
resistor during its idle state through some time. If the battery has been taken off for use on its
portable device, there is no re-charge check to conduct since the state transitions to the initial state
without the battery itself.
In some other cases, the preliminary charge stage which can be conducted as one step prior to the
phase-0 to assure the battery to be through the charge sequences has working functions to perform.
This stage would involve in applying constant-voltage charge pulses at defined level of 4.0v or so to
the battery, which was examined to determine if it’s at low voltage of 2.5v or less. The charge pulses
applied to the battery for a short period of 15 intervals with 10 seconds high (at 4.0v voltage beats)
and 5 seconds low (ground) each to examine if the battery voltage still remain low at 2.5v or less,
which is then considered as defective and should be discarded.
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FS3861
Rev. 1.0