ISL88731
Write to a Register
SLAVE
ADDR + W
REGISTER
ADDR
LO BYTE
DATA
HI BYTE
DATA
S
S
A
A
A
A
A
P
Read from a Register
SLAVE
ADDR + W
REGISTER
ADDR
SLAVE
LO BYTE
DATA
HI BYTE
DATA
A
P
S
A
A
N
P
ADDR + R
S
A
N
Start
Stop
Acknowledge
No Acknowledge
Driven by the master
Driven by ISL88731
P
FIGURE 18. SMBus/ISL88731 READ AND WRITE PROTOCOL
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 ISL88731 is controlled by the
data written to the registers described in Table 1.
Byte Format
Every byte put on the SDA line must be eight bits long and
must be followed by an acknowledge bit. Data is transferred
with the most significant bit first (MSB) and the least
significant bit last (LSB).
Battery Charger Registers
ISL88731 and SMBus
The ISL88731 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
ISL88731. On the ISL88731, ManufacturerID always returns
0x0049 (ASCII code for “I” for Intersil) and DeviceID always
returns 0x0001.
The ISL88731 receives control inputs from the SMBus
interface. The serial interface complies with the SMBus
protocols as documented in the System Management Bus
Specification V1.1, which can be downloaded from
www.smbus.org. The ISL88731 uses the SMBus Read-Word
and Write-Word protocols (Figure 18) to communicate with
the smart battery. The ISL88731 is an SMBus slave device
and does not initiate communication on the bus. It responds
to the 7-bit address 0b0001001_ (0x12).
Enabling and Disabling Charging
After applying power to ISL88731, 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.
Read address = 0b00010011 and
Write address = 0b00010010.
In addition, the ISL88731 has two identification (ID)
registers: a 16-bit device ID register and a 16-bit
manufacturer ID register.
TABLE 1. BATTERY CHARGER REGISTOR SUMMARY
REGISTER
ADDRESS
REGISTER NAME
ChargeCurrent
ChargeVoltage
InputCurrent
READ/WRITE
Read or Write
DESCRIPTION
6-Bit Charge Current Setting
POR STATE
0x0000
0x14
0x15
0x3F
0xFE
0xFF
Read or Write
Read or Write
Read Only
11-Bit Charge Voltage Setting
6-Bit Charge Current Setting
Manufacturer ID
0x0000
0x0080
ManufacturerID
DeviceID
0x0049
Read Only
Device ID
0x0001
FN9258.0
November 20, 2006
11
INTERSIL [ Intersil ]
