BQ29312_15 Datasheet, PDF (28/39 Pages) Texas Instruments – FOUR CELL LITHIUM-ION

bq29312
SLUS546E – MARCH 2003 – REVISED MARCH 2005
APPLICATION INFORMATION (continued)
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V_(PACK)
REG
PMS
Host =
Inactive
Host = Active
0.7 V
0V
3.3 V
0V
CHG
DSG
Battery
Voltage
Set to ”L” as
PMS = PACK
0V
Set to ”L” by Host
”L” (1 V)
0V
Host Sets
DSG-FET to ON
”L” (1 V)
Charge
Current
0V
Fast Charge Current
0 V and Precharge Current
0A
0 V Precharge Mode Fast Charge Mode
Figure 12. Signal Timing of Pins During 0 V Charging and Precharging (Common FET)
Precharge FET
This mode has a dedicated precharge current path using an additional open drain driven FET (PCHG-FET) and
sustains the V_(PACK) level. In this mode, where the PMS input is connected to GND, the bq29312 and host
combine to provide the precharge function by limiting the fast charge current which is provided by the system
side charger.
Figure 13 shows the bq29312 application circuit in this mode.
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