Datasheet

TPS65735
www.ti.com SLVSAI6–JUNE 2011
Figure 2-5. Battery Charge Phases
In the pre-charge phase, the battery is charged with the pre-charge current that is scaled to be 10% of the
fast-charge current set by the resistor connected to the ISET pin. Once the battery voltage crosses the
V
LOWV
threshold, the battery is charged with the fast-charge current (I
CHG
). As the battery voltage reaches
V
BAT(REG)
, the battery is held at a constant voltage of V
BAT(REG)
and the charge current tapers off as the
battery approaches full charge. When the battery current reaches I
TERM
, the charger indicates charging is
done by making the nCHG_STAT pin high impedance. Note that termination detection is disabled
whenever the charge rate is reduced from the set point because of the actions of the thermal loop, the
DPM loop, or the V
IN(LOWV)
loop.
2.7.2.1 Pre-charge
The value for the pre-charge current is set to be 10% of the charge current that is set by the external
resistor, R
ISET
. Pre-charge current is scaled to lower currents when the charger is in thermal regulation.
2.7.2.2 Charge Termination
In the fast charge state, once V
BAT
≥ V
BAT(REG)
, the charger enters constant voltage mode. In constant
voltage mode, the charge current will taper until termination when the charge current falls below the I
(TERM)
threshold (typically 10% of the programmed fast charge current). Termination current is not scaled when
the charger is in thermal regulation. When the charging is terminated, the nCHG_STAT pin will be high
impedance (effectively turning off any LED that is connected to this pin).
2.7.2.3 Recharge
Once a charge cycle is complete and termination is reached, the battery voltage is monitored. If V
BAT
<
V
BAT(REG)
- V
RCH
, the device determines if the battery has been removed. If the battery is still present, then
the recharge cycle begins and will end when V
BAT
≥ V
BAT(REG)
.
2.7.2.4 Charge Timers
The charger in this device has internal safety timers for the pre-charge and fast charge phases to prevent
potential damage to either the battery or the system. The default values for these timers are found as
follows: Pre-charge timer = 0.5 hours (30 minutes) and Fast charge timer = 5 hours (300 minutes).
Copyright © 2011, Texas Instruments Incorporated POWER MANAGEMENT CORE 17
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