ISL88731C
registers. Use the Write-Word protocol (Figure 20) to
Setting Charge Voltage
write to the ChargeVoltage register. The register address
for ChargeVoltage is 0x15. The 16-bit binary number
formed by D15–D0 represents the charge voltage set
point in mV. However, the resolution of the ISL88731C is
16mV because the D0–D3 bits are ignored as shown in
Table 2. The D15 bit is also ignored because it is not
needed to span the 1.024V to 19.2V range. Table 2
shows the mapping between the charge-voltage set point
and the 16-bit number written to the ChargeVoltage
register. The ChargeVoltage register can be read back to
verify its contents.
Charge voltage is set by writing a valid 16-bit number to
the ChargeVoltage register. This 16-bit number translates
to a 65.535V full-scale voltage. The ISL88731C ignores
the first 4 LSBs and uses the next 11 bits to set the
voltage DAC. The charge voltage range of the ISL88731C
is 1.024V to 19.200V. Numbers requesting charge
voltage greater than 19.200V result in a ChargeVoltage
of 19.200V. All numbers requesting charge voltage below
1.024V result in a voltage set point of zero, which
terminates charging. Upon initial power-up or reset, the
ChargeVoltage and ChargeCurrent registers are reset to
0 and the charger remains shut down until valid numbers
are sent to the ChargeVoltage and ChargeCurrent
TABLE 2. CHARGEVOLTAGE (REGISTER 0x15)
DESCRIPTION
BIT
0
BIT NAME
Not used.
Not used.
Not used.
Not used.
1
2
3
4
Charge Voltage, DACV 0
Charge Voltage, DACV 1
Charge Voltage, DACV 2
Charge Voltage, DACV 3
Charge Voltage, DACV 4
Charge Voltage, DACV 5
Charge Voltage, DACV 6
Charge Voltage, DACV 7
Charge Voltage, DACV 8
Charge Voltage, DACV 9
Charge Voltage, DACV 10
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 16mV of charger voltage.
5
6
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 32mV of charger voltage.
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 64mV of charger voltage.
7
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 128mV of charger voltage.
8
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 256mV of charger voltage.
9
0 = Adds 0mV of charger voltage, 1024mV min.
1 = Adds 512mV of charger voltage.
10
11
12
13
14
15
0 = Adds 0mA of charger voltage.
1 = Adds 1024mV of charger voltage.
0 = Adds 0mV of charger voltage.
1 = Adds 2048mV of charger voltage.
0 = Adds 0mV of charger voltage.
1 = Adds 4096mV of charger voltage.
0 = Adds 0mV of charger voltage.
1 = Adds 8192mV of charger voltage.
0 = Adds 0mV of charger voltage.
1 = Adds 16384mV of charger voltage, 19200mV max.
Not used. Normally a 32768mV weight.
FN6978.0
March 8, 2010
14
INTERSIL [ Intersil ]
