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BQ24080-Q1 Datasheet, PDF (11/28 Pages) Texas Instruments – Li-Ion and Li-Pol Automotive Charger
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www.ti.com
bq24080-Q1, bq24081-Q1
SLUSCB6 – MAY 2015
8.3 Feature Description
8.3.1 Battery Preconditioning
During a charge cycle, if the battery voltage is below the V(LOWV) threshold, the device applies a precharge
current, IO(PRECHG), to the battery. This feature revives deeply discharged cells. Resistor RSET, connected
between the ISET and VSS, determines the precharge rate. The V(PRECHG) and K(SET) parameters are specified in
the Electrical Characteristics table.
IO(PRECHG) =
K(SET) x V(PRECHG)
RSET
(1)
The device activates a safety timer, t(PRECHG), during the conditioning phase. If the V(LOWV) threshold is not
reached within the timer period, the device turns off the charger and enunciates FAULT on the STATx pins. See
the Timer Fault and Recovery section for additional details.
8.3.2 Battery Fast-Charge Constant Current
The device offers on-chip current regulation with programmable set point. Resistor RSET, connected between the
ISET and VSS, determines the charge rate. The V(SET) and K(SET) parameters are specified in the specifications
table.
K(SET) x V(SET)
IO(OUT) =
RSET
(2)
8.3.3 Charge-Current Monitor
When the charge function is enabled internal circuits generate a current proportional to the charge current at the
ISET pin. This current, when applied to the external charge current programming resistor RISET generates an
analog voltage that can be monitored by an external host to calculate the current sourced from the OUT pin.
V(ISET)
= I(OUT)
x
R(ISET)
K(ISET)
(3)
8.3.4 Battery Fast-Charge Voltage Regulation
The voltage regulation feedback is through the OUT pin. This input is tied directly to the positive side of the
battery pack. The device monitors the battery-pack voltage between the OUT and VSS pins. When the battery
voltage rises to the VO(REG) threshold, the voltage regulation phase begins and the charging current begins to
taper down.
As a safety backup, the device also monitors the charge time in the charge mode. If charge is not terminated
within this time period, t(CHG), the charger is turned off and FAULT is set on the STATx pins. See the Timer Fault
and Recovery section for additional details.
8.3.5 Charge Termination Detection and Recharge
The device monitors the charging current during the voltage regulation phase. Once the termination threshold,
I(TERM), is detected, charge is terminated. The V(TERM) and K(SET) parameters are specified in the Electrical
Characteristics table.
IO(TERM) =
K(SET) x V(TERM)
RSET
(4)
After charge termination, the device restarts the charge once the voltage on the OUT pin falls below the V(RCH)
threshold. This feature keeps the battery at full capacity at all times.
The device monitors the charging current during the voltage regulation phase. Once the termination threshold,
I(TERM), is detected, the charge is terminated immediately.
Resistor RSET, connected between the ISET and VSS, determines the current level at the termination threshold.
Copyright © 2015, Texas Instruments Incorporated
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