ISL95871C Datasheet, PDF (11/25 Pages) Intersil Corporation – SMBus Interfaced Battery Charger with Internal FETs

ISL95871C
Typical Operating Performance DCIN = 19V, 3S2P Li-Battery, T_A = +25°C, unless
otherwise noted. (Continued)
VCOMP
ICOMP
ICOMP
VCOMP
CSON
CSON
CHARGE CURRENT
FIGURE 17. BATTERY REMOVAL
CHARGE CURRENT
FIGURE 18. BATTERY INSERTION
ADAPTER CURRENT
SYSTEM CURRENT
CHARGE CURRENT
CSON VOLTAGE
FIGURE 19. SYSTEM LOAD TRANSIENT RESPONSE
Theory of Operation
Introduction
The ISL95871C includes all of the functions necessary to
charge 1- to 4-cell Li-ion and Li-polymer batteries. A high
efficiency synchronous buck converter is used to control
the charging voltage up to 19.2V and charging current up
to 8A. The ISL95871C also has input current limiting up
to 11A. The Input current limit, charge current limit and
charge voltage limit are set by internal registers written
with SMBus. The ISL95871C “Typical Application Circuit”
is shown in Figure 4.
The ISL95871C charges the battery with constant
charge current, set by the ChargeCurrent register, until
the battery voltage rises to a voltage set by the
ChargeVoltage register. The charger will then operate at
a constant voltage. The adapter current is monitored
and if the adapter current rises to the limit set by the
InputCurrent register, battery charge current is reduced
so the charger does not reduce the adapter current
available to the system.
The ISL95871C features a voltage regulation loop
(VCOMP) and 2 current regulation loops (ICOMP). The
VCOMP voltage regulation loop monitors VFB to limit the
battery charge voltage. The ICOMP current regulation
loop limits the battery charging current delivered to the
battery to ensure that it never exceeds the current set by
the ChargeCurrent register. The ICOMP current
regulation loop also limits the input current drawn from
the AC-adapter to ensure that it never exceeds the limit
set by the InputCurrent register, and to prevent a system
crash and AC-adapter overload.
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FN6856.1
September 29, 2010