Datasheet

bq24725A
www.ti.com SLUSAL0 –SEPTEMBER 2011
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 FAST_DPM threshold, the charger will reduce charging current to allow the input
current drop. After a typical 260-µs delay time, if input current is still above FAST_DPM threshold, the charger
will shut down. The charger will soft restart to charge the battery if the adapter still has power 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 bq24725A 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);
The first time after IC POR always gives 150ms ACOK rising edge delay no matter what the ChargeOption
register value is. Only after the ACDET pin voltage is pulled below 2.4V (but not below 0.6V, which resets the IC
and forces the next ACOK rising edge deglitch time to be 1.3s) and the ACFET has been turned off at least one
time, the 1.3s (or 150ms) delay time is effective for the next time the ACDET pin voltage goes above 2.4V. To
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