Datasheet

I
O(PRECHG)
+
K
(ISET2)
V
(ISET2)
ǒ
R
(ISET2)
R
(SNS)
Ǔ
R
(SNS)
+
V
IREG
I
OCHARGE
R
ISET1
+
K
ISET1
V
ISET1
R
SNS
I
CHARGE
OREG IBAT
(R1 + R2)
V = x V
R2
RCH
(R1 + R2)
V = x 50 mV
R2
bq24100, bq24103, bq24103A
bq24104, bq24105, bq24108, bq24109
bq24113, bq24113A, bq24115
www.ti.com SLUS606O –JUNE 2004–REVISED MARCH 2010
The magnitude of the precharge current, I
O(PRECHG)
, is determined by the value of programming resistor, R
(ISET2)
,
connected to the ISET2 pin.
(2)
where
R
SNS
is the external current-sense resistor
V
(ISET2)
is the output voltage of the ISET2 pin
K
(ISET2)
is the V/A gain factor
V
(ISET2)
and K
(ISET2)
are specified in the Electrical Characteristics table.
Battery Charge Current
The battery charge current, I
O(CHARGE)
, is established by setting the external sense resistor, R
(SNS)
, and the
resistor, R
(ISET1)
, connected to the ISET1 pin.
In order to set the current, first choose R
(SNS)
based on the regulation threshold V
IREG
across this resistor. The
best accuracy is achieved when the V
IREG
is between 100mV and 200mV.
(3)
If the results is not a standard sense resistor value, choose the next larger value. Using the selected standard
value, solve for V
IREG
. Once the sense resistor is selected, the ISET1 resistor can be calculated using the
following equation:
(4)
Battery Voltage Regulation
The voltage regulation feedback occurs through the BAT pin. This input is tied directly to the positive side of the
battery pack. The bqSWITCHER monitors the battery-pack voltage between the BAT and VSS pins. The
bqSWITCHER is offered in a fixed single-cell voltage version (4.2 V) and as a one-cell or two-cell version
selected by the CELLS input. A low or floating input on the CELLS selects single-cell mode (4.2 V) while a
high-input through a resistor selects two-cell mode (8.4 V).
For the bq24105 and bq24115, the output regulation voltage is specified as:
(5)
where R1 and R2 are resistor divider from BAT to FB and FB to VSS, respectively.
The bq24105 and bq24115 recharge threshold voltage is specified as:
(6)
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Product Folder Link(s): bq24100 bq24103 bq24103A bq24104 bq24105 bq24108 bq24109 bq24113 bq24113A
bq24115