Texas Instruments BQ25157, Manual

Page: 18 / 110

Table 9-1. Charge Enable Function Through CE Pin and CE Bit
CE PIN CHARGE _DISABLE BIT CHARGING
0 0 Enabled
0 1 Disabled
1 0 Disabled
1 1 Disabled
Figure 9-2 shows a typical charge cycle.
Figure 9-2. BQ25157 Typical Charge Cycle
9.3.1.1.1 Pre-Charge
In order to prevent damage to the battery, the device will charge the battery at a much lower current level when
the battery voltage (V
BAT
) is below the V
LOWV
level. The pre-charge current (I
PRECHARGE
) can be programmed
through I
2
C. Once the battery voltage reaches V
LOWV
, the charger will then operate in Fast Charge Mode,
charging the battery at I
CHARGE
.
During pre-charge, the safety timer is set to 25% of the safety timer value during fast charge.
9.3.1.1.2 Fast Charge
The charger has two main control loops that control charging when V
BAT
> V
LOWV
: the Constant Current (CC)
and Constant Voltage (CV) loops. When the CC loop is dominant, typically when V
BAT
< V
BATREG
– 50 mV, the
battery is charged at the maximum charge current level I
CHARGE
, unless there is a TS fault condition (JEITA
operation), thermal charge current foldback is active, VINDPM is active, or DPPM is active. (See respective
sections for details on these modes of operation.) Once the battery voltage approaches the V
BATREG
level, the
CV loop becomes more dominant and the charging current starts tapering off as shown in Figure 9-2 . Once the
charging current reaches the termination current (I
TERM
) charging is stopped. Note that to ensure that the battery
is charged to V
BATREG
level, the regulated PMID voltage should be set to at least 200mV above V
BATREG
.
BQ25157
SLUSEC5 – DECEMBER 2020
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