isl88731a Intersil Corporation, isl88731a Datasheet - Page 12

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

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).
ISL88731A and SMBus
The ISL88731A 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 ISL88731A uses the SMBus
Read-Word and Write-Word protocols (Figure 19) to
communicate with the smart battery. The ISL88731A is an
SMBus slave device and does not initiate communication on
the bus. It responds to the 7-bit address 0b0001001_ (0x12).
Read address = 0b00010011 and
Write address = 0b00010010.
In addition, the ISL88731A has two identification (ID)
registers: a 16-bit device ID register and a 16-bit
manufacturer ID register.
REGISTER
ADDRESS
0xFE
0xFF
0x14
0x15
0x3F
S
S
Write To A Register
SLAVE
ADDR + W
Read From A Register
SLAVE
ADDR + W
S
P
ChargeCurrent
ChargeVoltage
InputCurrent
ManufacturerID
DeviceID
START
STOP
REGISTER NAME
12
A
A
FIGURE 19. SMBus/ISL88731A READ AND WRITE PROTOCOL
REGISTER
REGISTER
ADDR
ADDR
TABLE 1. BATTERY CHARGER REGISTER SUMMARY
Read or Write
Read or Write
Read or Write
Read Only
Read Only
A
N
READ/WRITE
A
A
ACKNOWLEDGE
NO ACKNOWLEDGE
P
LO BYTE
DATA
ISL88731A
S
SLAVE
ADDR + R
6-bit Charge Current Setting
11-bit Charge Voltage Setting
6-bit Charge Current Setting
Manufacturer ID
Device ID
A
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 ISL88731A is controlled by
the data written to the registers described in Table 1.
Battery Charger Registers
The ISL88731A 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
ISL88731A. On the ISL88731A, ManufacturerID always
returns 0x0049 (ASCII code for “I” for Intersil) and DeviceID
always returns 0x0001.
Enabling and Disabling Charging
After applying power to ISL88731A, 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.
HI BYTE
DATA
A
LO BYTE
DESCRIPTION
DATA
A
DRIVEN BY THE MASTER
DRIVEN BY ISL88731
P
A
HI BYTE
DATA
N
POR STATE
P
0x0000
0x0000
0x0080
0x0049
0x0001
January 7, 2009
FN6738.1