BQ24725A_17 Datasheet, PDF (24/47 Pages) Texas Instruments – 1-4 Cell Li+ Battery SMBus Charge Controller with N-Channel Power MOSFET Selector and Advanced Circuit Protection

bq24725A
SLUSAL0A – SEPTEMBER 2011 – REVISED AUGUST 2014
www.ti.com
The SRP and SRN pins are used to sense R_SR with default value of 10mΩ. However, resistors of other values
can also be used. For a larger sense resistor, a larger sense voltage is given, and a higher regulation accuracy;
but, at the expense of higher conduction loss. If the current sensing resistor value is too high, it may trigger an
over current protection threshold because the current ripple voltage is too high. In such a case, either a higher
inductance value or a lower current sensing resistor value should be used to limit the current ripple voltage level.
A current sensing resistor value no more than 20mΩ is suggested.
To provide secondary protection, the bq24725A has an ILIM pin with which the user can program the maximum
allowed charge current. Internal charge current limit is the lower one between the voltage set by
ChargeCurrent(), and voltage on ILIM pin. To disable this function, the user can pull ILIM above 1.6V, which is
the maximum charge current regulation limit. Equation 2 shows the voltage set on ILIM pin with respect to the
preferred charge current limit:
( ) V_ILIM = 20 × V_SRP - V_SRN = 20 ´ I_CHG ´ R_SR
(2)
Figure 15. Charge Current Register (0x14H), Using 10mΩ Sense Resistor
15
Not in use
R/W
14
Not in use
13
Not in use
R/W
12
11
Charge
Current,
DACICHG 6
Charge
Current,
DACICHG 5
R/W R/W
10
Charge
Current,
DACICHG 4
R/W
9
Charge
Current,
DACICHG 3
R/W
7
6
5
4
Charge
Current,
DACICHG 1
Charge
Current,
DACICHG 0
Not in use
Not in use
R/W
R/W
R/W
R/W
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
3
Not in use
R/W
2
Not in use
R/W
1
Not in use
R/W
Table 4. Charge Current Register (0x14H), Using 10mΩ Sense Resistor
Bit Field
[15] Not in use
[14] Not in use
[13] Not in use
[12] Charge Current, DACICHG 6
[11] Charge Current, DACICHG 5
[10] Charge Current, DACICHG 4
[9]
Charge Current, DACICHG 3
[8]
Charge Current, DACICHG 2
[7]
Charge Current, DACICHG 1
[6]
Charge Current, DACICHG 0
[5]
Not in use
[4]
Not in use
[3]
Not in use
[2]
Not in use
[1]
Not in use
[0]
Not in use
Type
Reset
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Description
Not used.
Not used.
Not used.
0 = Adds 0mA of charger current.
1 = Adds 4096mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 2048mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 1024mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 512mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 256mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 128mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 64mA of charger current.
Not used.
Not used.
Not used.
Not used.
Not used.
Not used.
8
Charge
Current,
DACICHG 2
R/W
0
Not in use
R/W
24
Submit Documentation Feedback
Product Folder Links: bq24725A
Copyright © 2011–2014, Texas Instruments Incorporated