米6体育平台手机版

ZHCS229C September 2011 – January 2020 BQ24725A

PRODUCTION DATA.

封装选项

机械数据 (封装 | 引脚)

RGR|20
- MPQF239A

散热焊盘机械数据 (封装 | 引脚)

RGR|20
- QFND242E

订购信息

8.5.5 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 BQ24725A 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:

Equation 3. BQ24725A eq2_lusa79.gif

where η is the efficiency of the charger buck converter (typically 85% to 95%).

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 BQ24725A 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 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.

Figure 17. Input Current Register (0x3FH), Using 10mΩ Sense Resistor

15	14	13	12	11	10	9	8
Not in use	Not in use	Not in use	Input Current, DACIIN 5	Input Current, DACIIN 4	Input Current, DACIIN 3	Input Current, DACIIN 2	Input Current, DACIIN 1
R/W	R/W		R/W R/W		R/W	R/W	R/W

7	6	5	4	3	2	1	0
Input Current, DACIIN 0	Not in use	Not in use	Not in use	Not in use	Not in use	Not in use	Not in use
R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 6. Input Current Register (0x3FH), Using 10mΩ Sense Resistor

Bit	Field	Reset	Description
[15]	Not in use	R/W	Not used.
[14]	Not in use	R/W	Not used.
[13]	Not in use	R/W	Not used.
[12]	Input Current, DACIIN 5	R/W	0 = Adds 0mA of input current. 1 = Adds 4096mA of input current.
[11]	Input Current, DACIIN 4	R/W	0 = Adds 0mA of input current. 1 = Adds 2048mA of input current.
[10]	Input Current, DACIIN 3	R/W	0 = Adds 0mA of input current. 1 = Adds 1024mA of input current.
[9]	Input Current, DACIIN 2	R/W	0 = Adds 0mA of input current. 1 = Adds 512mA of input current.
[8]	Input Current, DACIIN 1	R/W	0 = Adds 0mA of input current. 1 = Adds 256mA of input current.
[7]	Input Current, DACIIN 0	R/W	0 = Adds 0mA of input current. 1 = Adds 128mA of input current.
[6]	Not in use	R/W	Not used.
[5]	Not in use	R/w	Not used.
[4]	Not in use	R/W	Not used.
[3]	Not in use	R/W	Not used.
[2]	Not in use	R/W	Not used.
[1]	Not in use	R/W	Not used.
[0]	Not in use	R/W	Not used.