MAX17035(2009) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX17035
(Rev.:2009)

High-Frequency, Low-Cost SMBus Chargers

Maxim Integrated 

High-Frequency,

Low-Cost SMBus Chargers

Table 5. ChargeCurrent() (0x14) (10mI Sense Resistor, RS2) (continued)

BIT

BIT NAME

DESCRIPTION

9

Charge Current, DACI 2

0 = Adds 0mA of charger current compliance.

1 = Adds 512mA of charger current compliance.

10

Charge Current, DACI 3

0 = Adds 0mA of charger current compliance.

1 = Adds 1024mA of charger current compliance.

11

Charge Current, DACI 4

0 = Adds 0mA of charger current compliance.

1 = Adds 2048mA of charger current compliance.

12

Charge Current, DACI 5

0 = Adds 0mA of charger current compliance.

1 = Adds 4096mA of charger current compliance, 8064mA max

13

—

Not used. Normally a 8192mA weight.

14

—

Not used. Normally a 16386mA weight.

15

—

Not used. Normally a 32772mA weight.

Setting Input-Current Limit

System current normally fluctuates as portions of the

system are powered up or put to sleep. By using the input-

current-limit circuit, the output-current requirement of the

AC wall adapter can be lowered, reducing system cost.

The total input current is the sum of the system supply

current, the charge current flowing into the battery, and

the current required by the charger. When the input

current exceeds the input current limit set with the

InputCurrent() command, the MAX17035/MAX17435/

MAX17535 reduce the charge current to provide priority

to system load current. As the system supply current

increases, the charge current is reduced as needed

to maintain the total input current at the input current

limit. The MAX17035/MAX17435/MAX17535 decrease

the charge current to zero, if necessary, to reduce the

input current to the input current limit. Thereafter, if the

system current continues to increase, there is nothing the

MAX17035/MAX17435/MAX17535 can do to maintain the

input current at the input current limit. If the system current

continues to increase the total input current can increase

until the ACOCP threshold (which is 1.3 x maximum

DAC setting) is reached and the MAX17035/MAX17435/

MAX17535 drive PDSL low to remove the input voltage.

The MAX17035/MAX17435/MAX17535 wait 0.6s and

then try to charge again; after a 16ms blanking period if

the current is again over the ACOCP threshold, it again

opens up the input voltage. It goes through this cycle

three times; after three times, the MAX17035/MAX17435/

MAX17535 wait for the adapter voltage to be removed

and reinserted before it reconnects the input voltage.

The total input current can be estimated as follows:

IINPUT = ISYSTEM + ICHARGER +

[(ICHARGE × VBATTERY) (VIN × η)]

where E is the efficiency of the DC-DC converter (typically

85% to 95%).

To set the input current limit, issue the SMBus command

InputCurrent() using the 16-bit data format listed in

Table 6. The InputCurrent() command uses the write-

word protocol (see Figure 3). The command code for

InputCurrent() is 0x3F (0b00111111). When RS1 = 10mI,

the MAX17035/MAX17435/MAX17535 provide an input

current-limit range of 256mA to 11.004A with 256mA

resolution. If a resistor RS other than 10mI is used, the

input current limit is scaled by a factor of 10mI/RS1.

InputCurrent() settings from 1mA to 128mA result in a

current limit of 128mA. Upon reset, the input current limit

is 128mA.

Setting Relearn Voltage

To set the relearn voltage issue, the SMBus command

RelearnVoltage() uses the 16-bit data format listed in

Table 7. The RelearnVoltage() command uses the

write-word and read-word protocols (see Figure 3).

The command code for RelearnVoltage() is 0x3D

(0b00111101). The MAX17035/MAX17435/MAX17535

provide a charge-voltage range of 4.095V to 19.200V

with 16mV resolution. When the relearn function is

enabled by setting bit 0 to 1, the PDSL pin switches off

the input-voltage FET and switches on the battery FET,

enabling discharging of the battery. The battery voltage

is monitored until the battery voltage reaches the relearn

voltage and thus a known low state of charge. The PDSL

state is then reset to allow charging and bit 0 is set to zero.

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