isl88731a Intersil Corporation, isl88731a Datasheet - Page 14

• Manufacturer Part Number: isl88731a
• Description: Smbus Level 2 Battery Charger
• Manufacturer: Intersil Corporation

Setting Charge Current
ISL88731A has a 16-bit ChargeCurrent register that sets the
battery charging current. ISL88731A 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
LSB translates to 1mA charge current. The ISL88731A
ignores the first 7 LSBs and uses the next 6 bits to control
the current DAC. The charge-current range of the
ISL88731A 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 0
BIT
10
12
13
14
15
11
0
1
2
3
4
5
6
7
8
9
Charge Current, DACI 0
Charge Current, DACI 1
Charge Current, DACI 2
Charge Current, DACI 3
Charge Current, DACI 4
Charge Current, DACI 5
sense
TABLE 3. CHARGE CURRENT (REGISTER 0x14) (10m Ω SENSE RESISTOR, RS2)
BIT NAME
14
resistor (RS2 in Figure 2), the
Not used
Not used
Not used
Not used
Not used
Not used
Not used
0 = Adds 0mA of charger current
1 = Adds 128mA of charger current
0 = Adds 0mA of charger current
1 = Adds 256mA of charger current
0 = Adds 0mA of charger current
1 = Adds 512mA of charger current
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
Not used
Not used
Not used
ISL88731A
and the charger is disabled. To start the charger, write valid
numbers to the ChargeVoltage and ChargeCurrent registers.
The ChargeCurrent register uses the Write-Word protocol
(see Figure 19). 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.
The ISL88731A 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.
DESCRIPTION
January 7, 2009
FN6738.1