BQ24747 Datasheet, PDF (25/36 Pages) Texas Instruments – SMBus-Controlled Level 2 Multi-Chemistry Battery Charger With Input Current Detect Comparator and Charge Enable Pin

bq24747
www.ti.com ............................................................................................................................................................................................. SLUS988 – OCTOBER 2009
SETTING THE CHARGE CURRENT
To set the charge current, use the SMBus to write a 16bit ChargeCurrent() command using the data format listed
in Table 4. The ChargeCurrent() command uses the Write-Word protocol (see Figure 34). The command code for
ChargeCurrent() is 0x14 (0b00010100). When using a 10-mΩ sense resistor, the bq24747 provides a
charge-current range of 128 mA to 8.064 A, with 128 mA resolution. Set ChargeCurrent() to 0 to terminate
charging. Upon reset, the ChargeVoltage() and ChargeCurrent() values are cleared and the charger remains off
until both the ChargeVoltage() and the ChargeCurrent() commands are received. Both UGATE and LGATE pins
remain low until the charger is restarted.
The bq24747 includes a foldback current limit when the battery voltage is low. If the battery voltage is less than
2.5 V, the charge current is temporarily set to 128 mA. The ChargeCurrent() register value is preserved, and
becomes active again when the battery voltage is higher than 2.7 V. This function effectively provides a fold-back
current limit, protecting the charger during short circuit and overload.
Table 4. Charge Current Register (0x14), Using 10mΩ Sense Resistor
BIT
BIT NAME
DESCRIPTION
0
–
Not used.
1
–
Not used.
2
–
Not used.
3
–
Not used.
4
–
Not used.
5
–
Not used.
6
–
Not used.
7
Charge Current, DACI 0
0 = Adds 0 mA of charger current
1 = Adds 128 mA of charger current.
8
Charge Current, DACI 1
0 = Adds 0 mA of charger current
1 = Adds 256 mA of charger current.
9
Charge Current, DACI 2
0 = Adds 0 mA of charger current
1 = Adds 512 mA of charger current
10
Charge Current, DACI 3
0 = Adds 0 mA of charger current.
1 = Adds 1024 mA of charger current.
11
Charge Current, DACI 4
0 = Adds 0 mA of charger current.
1 = Adds 2048 mA of charger current.
12
Charge Current, DACI 5
0 = Adds 0 mA of charger current.
1 = Adds 4096 mA of charger current, 8064 mA.
13
–
Not used.
14
–
Not used.
15
–
Not used.
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s) :bq24747
Submit Documentation Feedback
25