MAX17435 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX17435 Datasheet PDF : 27 Pages
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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 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
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 MAX17435/MAX17535
can do to maintain the input current at the input current
limit. If the system current continues to increase so that
the input current exceeds the ACOCP threshold (130%
of InputCurrent() setting) for more than 16ms (typ), the
MAX17435/MAX17535 drive PDSL low, which turns off the
adapter selector FETs and disconnects the adapter from
the system. After waiting 0.6s, the MAX17435/MAX17535
re-enable PDSL. If the ACOCP fault occurs again, the
MAX17435/MAX17535 drive PDSL low again after the
16ms (typ) delay. This cycle is repeated a maximum
of three times, after which the MAX17435/MAX17535
are latched off, and need to be reset by removing and
reinserting the adapter.
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, use the SMBus to write a
16-bit InputCurrent() using the data format listed in Table
6. The InputCurrent() command uses the write-word
and read-word protocols (see Figure 3). The command
code for InputCurrent() is 0x3F (0b00111111). When RS1
= 10mI, the 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 256mA result in a
current limit of 256mA. Upon reset, the input current limit
is 256mA.
Setting Relearn Voltage
To set the relearn voltage, use the SMBus to write a 16-bit
RelearnVoltage() command using the 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 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 MAX17435/MAX17535 drive PDSL low,
turning off the adapter selector FETs and turning on the
battery selector FET. This allows the battery to discharge
by powering the system while the adapter is still present.
The battery voltage is monitored until the battery voltage
reaches the relearn voltage corresponding to a known low
state of charge. The relearn bit 0 is set to zero, and PDSL
is re-enabled.
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