ISL88731
0 and the charger is disabled. To start the charger, write valid
Setting Charge Current
numbers to the ChargeVoltage and ChargeCurrent registers.
The ChargeCurrent register uses the Write-Word protocol
(Figure 18). The register code for ChargeCurrent is 0x14
(0b00010100). Table 3 shows the mapping between the
charge current set point and the ChargeCurrent number. The
ChargeCurrent register can be read back to verify its
contents.
ISL88731 has a 16-bit ChargeCurrent register that sets the
battery charging current. ISL88731 controls the charge
current by controlling the CSOP-CSON voltage. The
register’s LSB translates to 10µV at CSON-CSOP. With a
10mΩ charge current R
resistor (RS2 in “TYPICAL
sense
APPLICATION CIRCUIT” on page 2), the LSB translates to
1mA charge current. The ISL88731 ignores the first 7 LSBs
and uses the next 6 bits to control the current DAC. The
charge-current range of the ISL88731 is 0 to 8.064A (using a
10mΩ current-sense resistor). All numbers requesting
charge current above 8.064A result in a current setting of
8.064A. All numbers requesting charge current between
0mA to 128mA result in a current setting of 0mA. The default
charge current setting at Power-On Reset (POR) is 0mA. To
stop charging, set ChargeCurrent to 0. Upon initial power up,
the ChargeVoltage and ChargeCurrent registers are reset to
The ISL88731 includes a fault limiter for low battery
conditions. If the battery voltage is less than 2.5V, the charge
current is temporarily set to 128mA. The ChargeCurrent
register is preserved and becomes active again when the
battery voltage is higher than 2.7V. This function effectively
provides a foldback current limit, which protects the charger
during short circuit and overload.
TABLE 3. CHARGE CURRENT (REGISTER 0x14) (10mΩ SENSE RESISTOR, RS2)
BIT
0
BIT NAME
DESCRIPTION
Not used.
Not used.
Not used.
Not used.
Not used.
Not used.
Not used.
1
2
3
4
5
6
7
Charge Current, DACI 0
Charge Current, DACI 1
Charge Current, DACI 2
Charge Current, DACI 3
Charge Current, DACI 4
Charge Current, DACI 5
0 = Adds 0mA of charger current.
1 = Adds 128mA of charger current.
8
0 = Adds 0mA of charger current.
1 = Adds 256mA of charger current.
9
0 = Adds 0mA of charger current.
1 = Adds 512mA of charger current.
10
11
12
0 = Adds 0mA of charger current.
1 = Adds 1024mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 2048mA of charger current.
0 = Adds 0mA of charger current.
1 = Adds 4096mA of charger current, 8064mA max.
13
14
15
Not used.
Not used.
Not used.
FN9258.0
November 20, 2006
13
INTERSIL [ Intersil ]
