isl88731c Intersil Corporation, isl88731c Datasheet - Page 14

• Manufacturer Part Number: isl88731c
• Description: Smbus Level 2 Battery Charger
• Manufacturer: Intersil Corporation

The data (SDA) and clock (SCL) pins have Schmitt-
trigger inputs that can accommodate slow edges. Choose
pull-up resistors for SDA and SCL to achieve rise times
according to the SMBus specifications. The ISL88731C is
controlled by the data written to the registers described
in Table 1.
Battery Charger Registers
The ISL88731C supports five battery-charger registers
that use either Write-Word or Read-Word protocols, as
summarized in Table 1. ManufacturerID and DeviceID are
“read only” registers and can be used to identify the
ISL88731C. On the ISL88731C, ManufacturerID always
returns 0x0049 (ASCII code for “I” for Intersil) and
DeviceID always returns 0x0001.
Enabling and Disabling
Charging
After applying power to ISL88731C, the internal registers
contain their POR values (see Table 1). The POR values
for charge current and charge voltage are 0x0000. These
values disable charging. To enable charging, the
ChargeCurrent register must be written with a number
>0x007F and the ChargeVoltage register must be written
with a number >0x000F. Charging can be disabled by
writing 0x0000 to either of these registers.
BIT
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
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
BIT NAME
14
TABLE 2. CHARGEVOLTAGE (REGISTER 0x15)
Not used.
Not used.
Not used.
Not used.
1 = Adds 16mV of charger voltage.
1 = Adds 32mV of charger voltage.
1 = Adds 64mV of charger voltage.
1 = Adds 128mV of charger voltage.
1 = Adds 256mV of charger voltage.
1 = Adds 512mV of charger voltage.
1 = Adds 1024mV of charger voltage.
1 = Adds 2048mV of charger voltage.
1 = Adds 4096mV of charger voltage.
1 = Adds 8192mV of charger voltage.
1 = Adds 16384mV of charger voltage, 19200mV max.
Not used. Normally a 32768mV weight.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mV of charger voltage, 1024mV min.
0 = Adds 0mA of charger voltage.
0 = Adds 0mV of charger voltage.
0 = Adds 0mV of charger voltage.
0 = Adds 0mV of charger voltage.
0 = Adds 0mV of charger voltage.
ISL88731C
Setting Charge Voltage
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
registers. Use the Write-Word protocol (Figure 21) to
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.
DESCRIPTION
September 9, 2010
FN6978.1