BQ25060_1 Datasheet, PDF (13/24 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, and External Power Path Control

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Charger Operation With External Power Path Control Mode Disabled (BGATE = VSS)
PRECHARGE CC FAST CHARGE
CV TAPER
bq25060
SLUSA32 – MAY 2010
V_OUT(REG)
I_IN(LIM)
Battery
Current
V_LOWV
I_PRECHG
I_TERM
Battery and
Output
Voltage
CHG = Hi-Z
Figure 19. Charging Cycle with External Power Path Control Disabled (BGATE = VSS)
Precharge Mode (V_BAT ≤ V_LOWV)
The bq25060 enters precharge mode when V_BAT ≤ V_LOWV. Upon entering precharge mode, CHG goes low and
the input current limit is set to I_PRECHARGE. With BGATE connected to GND, the system output is connected to the
battery and therefore the system voltage is equal to the battery voltage. During precharge mode, the input
current is regulated to 50mA and as such, only loads up to 50mA are supported.
Normal CC/CV Mode
Once V_BAT > V_LOWV, the bq25060 enters constant current (CC) mode where charge current is regulated using the
internal MOSFETs between IN and OUT. The total current is shared between the output load and the battery.
Once the battery voltage charges up to VBAT(REG), the bq25060 enters constant voltage (CV) mode where
V_BAT is regulated to VBAT(REG) and the current is reduced. Once the input current falls below the termination
threshold (I_TERM), CHG goes high impedance but the system remains charging and regulates the output to
V_BAT(REG).
Programmable Input Current Limit (ISET)
When the charger is enabled, and the user programmable current limit is selected by the EN input, internal
circuits generate a current proportional to the input current at the ISET input. The current out of ISET is 1/1000
(±10%) of the charge current. This current, when applied to the external charge current programming resistor, R1
(Figure 1), generates an analog voltage that is regulated to program the fast charge current. Connect a resistor
from ISET to VSS to program the input current limit using the following equation:
I_{IN_LIMIT}
=
K_ISET
R_ISET
= ^{1000A ´ W}
R_ISET
(1)
IIN_LIM is programmable from 100mA to 1A. The voltage at ISET can be monitored by an external host to
calculate the charging current to the battery. The input current is related to the ISET voltage using the following
equation:
1000
I_IN
=
V_ISET
´
R_ISET
(2)
Monitoring the ISET voltage allows for the host to calculate the actual charging current and therefore perform
more accurate termination. The input current to the system must be monitored and subtracted from the current
into the bq25060 which is show by VISET.
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq25060
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