BQ24765_15 Datasheet, PDF (20/37 Pages) Texas Instruments – SMBus-Controlled Multi-Chemistry Battery Charger With Integrated Power MOSFETs

bq24765
SLUS999 – NOVEMBER 2009
A
B
tLOW tHIGH
SMBCLK
SMBDATA
C
D
EF
G
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H
I
J
K
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS C LOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW I = ACKNOWLEDGE CLOCK PULSE
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER J = STOP CONDITION
G = MSB OF DATA CLOCKED INTO MASTER K = NEW START CONDITION
H = LSB OF DATA CLOCKED INTO MASTER
Figure 30. SMBus Read Timing
BATTERY VOLTAGE REGULATION
The bq24765 uses a high-accuracy voltage regulator for charging voltage. The battery voltage regulation setting
is programmed by the host microcontroller (µC), through the SMBus interface that sets an 11 bit DAC. The
battery termination voltage is function of the battery chemistry. Consult the battery manufacturer to determine this
voltage.
The VFB pin is used to sense the battery voltage for voltage regulation and should be connected as close to the
battery as possible, or directly on the output capacitor. A 0.1-µF ceramic capacitor from VFB to AGND is
recommended to be as close to the VFB pin as possible to decouple high frequency noise.
To set the output charge voltage regulation limit, use the SMBus to write a 16bit ChargeVoltage() command
using the data format listed in Table 3. The ChargeVoltage() command uses the Write-Word protocol (see
Figure 28). The command code for ChargeVoltage() is 0x15 (0b00010101). The bq24765 provides a 1.024V to
19.200V charge voltage range, with 16mV resolution. Setting ChargeVoltage() below 1.024V or above 19.2V
clears DAC, and terminates charge.
Upon reset, the ChargeVoltage() and ChargeCurrent() values are cleared (0) and the charger remains off until
both the ChargeVoltage() and the ChargeCurrent() command are sent. During reset, both high side and low side
fets remain off until the charger gets started.
Table 3. Charge Voltage Register (0x15)
BIT
BIT NAME
DESCRIPTION
0
–
Not used
1
–
Not used
2
–
Not used
3
–
Not used
4
Charge Voltage, DACV 0
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 16mV of charger voltage
5
Charge Voltage, DACV 1
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 32mV of charger voltage
6
Charge Voltage, DACV 2
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 64mV of charger voltage
7
Charge Voltage, DACV 3
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 128mV of charger voltage.
8
Charge Voltage, DACV 4
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 256mV of charger voltage.
9
Charge Voltage, DACV 5
0 = Adds 0mV of charger voltage, 1024mV min
1 = Adds 512mV of charger voltage.
10
Charge Voltage, DACV 6
0 = Adds 0mV of charger voltage
1 = Adds 1024mV of charger voltage
11
Charge Voltage, DACV 7
0 = Adds 0mV of charger voltage
1 = Adds 2048mV of charger voltage
20
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