Datasheet

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0 V Precharge Mode
Fast Charge Mode
V
(PACK)
REG
PMS
CHG
DSG
Battery
Voltage
Charge
Current
Host =
Inactive
Host = Active
Set to ”L” as
PMS = PACK
Set to ”L” by Host
Host Sets
DSG-FET to ON
0.7 V
0 V
3.3 V
0 V
0 V
”L” (1 V)
0 V
”L” (1 V)
0 V
Fast Charge Current
0 V and Precharge Current
0 A
Precharge FET
bq29312A
SLUS629A – JANUARY 2005 – REVISED AUGUST 2005
APPLICATION INFORMATION (continued)
Figure 12. Signal Timing of Pins During 0-V Charging and Precharging (Common 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 bq29312A 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 bq29312A application circuit in this mode.
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