BQ24250C_15 Datasheet, PDF (20/46 Pages) Texas Instruments – bq24250C 2A Single Input I2C, Standalone Switch-Mode Li-Ion Battery Charger with Power-Path Management

bq24250C
SLUSBY7 – JULY 2014
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8.4.3 I²C Operation (Host Mode / Default Mode)
There are two primary modes of operation when interacting with the charge parameters of the bq24250C
charger: 1) Host mode operation where the I²C registers set the charge parameters, and 2) Default mode where
the register defaults set the charge parameters.
Figure 18 illustrates the behavior of the bq24250C when transitioning between host mode and stand alone mode:
Battery or Input
is Inserted
No
V_IN or V_BAT GOOD?
Yes
No
I2C command received?
Yes
ILIM=Register Value
VDPM=Register Value
ISET=Register Value
ILIM=EN1/EN2
VDPM=External Default
ISET=External Default
No
Yes
50s Watchdog Expired?
Host Mode
Figure 18. Host Mode and Stand Alone Mode Handoff
Once the battery or input is inserted and above the good thresholds, the device determines if an I²C command
has been received in order to discern whether to operate from the I²C registers or the internal register defaults. In
stand-alone mode the input current limit is set by the EN1/EN2 pins. If the watch dog timer is enabled, the device
will enter stand alone operation once the watchdog timer expires and re-initiate the default charge settings.
8.4.4 External Settings: ISET, ILIM and VIN_DPM
If the external resistor settings are used, the following equations can be followed to configure the charge settings.
The fast charge current resistor (R_ISET) can be set by using the following formula:
R_ISET
K_ISET
= _IFC
=
250
I_FC
(1)
Where I_FC is the desired fast charge current setting in Amperes.
The input current limit resistor (R_ILIM) can be set by using the following formula:
R_ILIM
=
K_ILIM
I_IC
=
270
I_IC
(2)
20
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