BQ24735_17 Datasheet, PDF (25/46 Pages) Texas Instruments – 1- to 4-Cell Li+ Battery SMBus Charge Controller for Supporting Turbo Boost Mode With N-Channel Power MOSFET Selector

www.ti.com
bq24735
SLUSAK9B – SEPTEMBER 2011 – REVISED APRIL 2015
9.6.5 Setting the Charge Voltage
To set the output charge regulation voltage, write a 16-bit ChargeVoltage() command (0x15H or 0b0001#0101)
using the data format listed in Table 5. The bq24735 provides charge voltage range from 1.024 V to 19.200 V,
with a 16-mV step resolution. Sending ChargeVoltage() below 1.024 V or above 19.2 V clears the register and
terminates charging. Upon POR, charge voltage limit is 0 V.
The SRN pin is used to sense the battery voltage for voltage regulation and should be connected as close to the
battery as possible. Place a decoupling capacitor (0.1 µF recommended) as close to the IC as possible to
decouple high-frequency noise.
Table 5. Charge Voltage Register (0x15H)
BIT
BIT NAME
DESCRIPTION
0
-
Not used.
1
-
Not used.
2
-
Not used.
3
-
Not used.
4
Charge Voltage, DACV 0 0 = Adds 0 mV of charger voltage.
1 = Adds 16 mV of charger voltage.
5
Charge Voltage, DACV 1 0 = Adds 0 mV of charger voltage.
1 = Adds 32 mV of charger voltage.
6
Charge Voltage, DACV 2 0 = Adds 0 mV of charger voltage.
1 = Adds 64 mV of charger voltage.
7
Charge Voltage, DACV 3 0 = Adds 0 mV of charger voltage.
1 = Adds 128 mV of charger voltage.
8
Charge Voltage, DACV 4 0 = Adds 0 mV of charger voltage.
1 = Adds 256 mV of charger voltage.
9
Charge Voltage, DACV 5 0 = Adds 0 mV of charger voltage.
1 = Adds 512 mV of charger voltage.
10
Charge Voltage, DACV 6 0 = Adds 0 mV of charger voltage.
1 = Adds 1024 mV of charger voltage.
11
Charge Voltage, DACV 7 0 = Adds 0 mV of charger voltage.
1 = Adds 2048 mV of charger voltage.
12
Charge Voltage, DACV 8 0 = Adds 0 mV of charger voltage.
1 = Adds 4096 mV of charger voltage.
13
Charge Voltage, DACV 9 0 = Adds 0 mV of charger voltage.
1 = Adds 8192 mV of charger voltage.
14
Charge Voltage, DACV 10 0 = Adds 0 mV of charger voltage.
1 = Adds 16384 mV of charger voltage.
15
-
Not used.
9.6.6 Setting Input Current
System current normally fluctuates as portions of the system are powered up or put to sleep. With the input
current limit, the output current requirement of the AC wall adapter can be lowered, reducing system cost.
The total input current, from a wall cube or other DC source, is the sum of the system supply current and the
current required by the charger. When the input current exceeds the set input current limit, the bq24735
decreases the charge current to provide priority to system load current. As the system current rises, the available
charge current drops linearly to zero. Thereafter, all input current goes to system load and input current
increases.
During DPM regulation, the total input current is the sum of the device supply current I_BIAS, the charger input
current, and the system load current I_LOAD, and can be estimated as follows:
I_INPUT
= I_LOAD
+
é
ê
ë
I_BATTERY ´
V_IN
V_BATTERY
´η
ù
ú
û
+ I_BIAS
where
• η is the efficiency of the charger buck converter (typically 85% to 95%).
(3)
Copyright © 2011–2015, Texas Instruments Incorporated
Product Folder Links: bq24735
Submit Documentation Feedback
25