Datasheet

V
LOWV
V
RECH
I
PRECH
& I
TERM
Precharge
Time
FastchargeSafetyTime
Precharge
Current
Regulation
Phase
FastchargeCurrent
RegulationPhase
FastchargeVoltage
RegulationPhase
Termination
Charge
Voltage
Charge
Current
RegulationCurrent
RegulationVoltage
BAT
R2
V = 1.8 V 1
R1
é ù
´ +
ê ú
ë û
ISET
CHARGE
SR
V
I =
20 R´
bq24620
SLUS893A –MARCH 2010– REVISED OCTOBER 2011 www.ti.com
DETAILED DESCRIPTION
Figure 11. Typical Charging Profile
BATTERY VOLTAGE REGULATION
The bq24620 uses a high-accuracy voltage band gap and regulator for the charging voltage. The charge voltage
is programmed via a resistor divider from the battery to ground, with the midpoint tied to the VFB pin. The
voltage at the VFB pin is regulated to 1.8 V, giving Equation 1 for the regulation voltage:
(1)
where R2 is connected from VFB to the battery and R1 is connected from VFB to GND.
BATTERY CURRENT REGULATION
The ISET1 input sets the maximum charging current. Battery current is sensed by resistor R
SR
connected
between SRP and SRN. The full-scale differential voltage between SRP and SRN is 100 mV. Thus, for a 10-mΩ
sense resistor, the maximum charging current is 10 A. Equation 2 is for charge current
(2)
V
ISET
, the input voltage range of ISET is between 0 and 2 V. The SRP and SRN pins are used to sense voltage
across R
SR
with default value of 10 mΩ. However, resistors of other values can also be used. A larger sense
resistor gives a larger sense voltage and a higher regulation accuracy, but at the expense of higher conduction
loss.
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Product Folder Link(s): bq24620