Datasheet

Not Recommended for New Designs
bq24725
SLUS702A –JULY 2010–REVISED NOVEMBER 2010 www.ti.com
To set the input current limit, write a 16-bit InputCurrent() command (0x3FH or 0b00111111) using the data
format listed in Table 6. When using a 10mΩ sense resistor, the bq24725 provides an input-current limit range of
128mA to 8.064A, with 128mA resolution. The suggested input current limit is set to no less than 512mA.
Sending InputCurrent() below 128mA or above 8.064A clears the register and terminates charging. Upon POR,
the default input current limit is 4096mA.
The ACP and ACN pins are used to sense R
AC
with default value of 10mΩ. However, resistors of other values
can also be used. For a larger sense resistor, larger sense voltage is given, and a higher regulation accuracy;
but, at the expense of higher conduction loss.
If input current rises above 108% of input current limit set point, the charger will shut down immediately to allow
the input current drop. After charging stops, the charger will soft restart to charge the battery if the adapter still
has power left to charge the battery. This prevents a crash if the adapter is overloaded when the system has a
high and fast loading transient. The waiting time between shut down and restart charging is a natural response
time of the input current limit loop.
Table 6. Input Current Register (0x3FH), 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 Input Current, DACIIN 0 0 = Adds 0mA of input current.
1 = Adds 128mA of input current.
8 Input Current, DACIIN 1 0 = Adds 0mA of input current.
1 = Adds 256mA of input current.
9 Input Current, DACIIN 2 0 = Adds 0mA of input current.
1 = Adds 512mA of input current.
10 Input Current, DACIIN 3 0 = Adds 0mA of input current.
1 = Adds 1024mA of input current.
11 Input Current, DACIIN 4 0 = Adds 0mA of input current.
1 = Adds 2048mA of input current.
12 Input Current, DACIIN 5 0 = Adds 0mA of input current.
1 = Adds 4096mA of input current.
13 – Not used.
14 – Not used.
15 – Not used.
Adapter Detect and ACOK Output
The bq24725 uses an ACOK comparator to determine the source of power on VCC pin, either from the battery or
adapter. An external resistor voltage divider attenuates the adapter voltage before it goes to ACDET. The
adapter detect threshold should typically be programmed to a value greater than the maximum battery voltage,
but lower than the maximum allowed adapter voltage.
The open drain ACOK output requires external pull up resistor to system digital rail for a high level. It can be
pulled to external rail under the following conditions:
• V
VCC
> UVLO;
• 2.4V < V
ACDET
< 3.15V (not in ACOVP condition, nor in low input voltage condition);
• V
VCC
–V
SRN
> 275mV (not in sleep mode);
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