LTC1760
17
1760fc
For more information
www.linear.com/LTC1760
OPERATION
2.3 Description of Supported SMBus Functions
The functions are described as follows:
Function Name() (command code)
Description:
A brief description of the function.
Purpose:
The purpose of the function, and an example where ap-
propriate.
SMBus Protocol:
Refer to Section 2.5 and to the SMBus
specification for more details.
Input, Output or Input/Output:
A description of the data
supplied to, or returned by, the function.
Whenever the LTC1760 encounters a valid command with
invalid data, it ACKs the command, and ignores the invalid
data. For example, if an attempt is made to select Battery
1 and 2 to simultaneously communicate with the system
host, the LTC1760 will just ignore the request.
2.3.1 BatterySystemState() (0
×
01)
Description:
This function returns the present state of the LTC1760 and
allows access to individual batteries. The information is
broken into four nibbles that report:
Which battery is communicating with the SMBus Host
Which batteries, if any, or AC is powering the system
Which batteries are connected to the Smart Charger
Which batteries are present.
The LTC1760 provides a mechanism to notify the system
whenever there is a change in its state. Specifically, the
LTC1760 provides the system with a notification whenever:
• A battery is added or removed (Polling or
SMBALERT
).
• AC power is connected or disconnected (Polling or
SMBALERT
).
• The LTC1760 autonomously changes the configura-tion
of the batteries supplying power (Polling only).
• The LTC1760 autonomously changes the configuration
of the batteries being charged (Polling only).
Purpose:
Used by the SMBus Host to determine the present state
of the LTC1760 and the attached batteries. It also may be
used to determine the state of the battery system after
the LTC1760 notifies the SMBus Host of a change via
SMBALERT
.
SMBus Protocol:
Read or Write Word.
Input/Output:
word – Refer to “Section 2.2” for bit
mapping.
SMB_BAT[4:1] Nibble
The read/write SMB_BAT[4:1] nibble is used by the SMBus
Host to select with which individual battery to commu-
nicate or to determine with which individual battery it is
communicating.
For example, an application that displays the remaining
capacity of all batteries would write to this nibble to in-
dividually select each battery in turn and get its capacity.
Allowed values are:
0010b: SMBus Host is communicating with Battery 2.
0001b: SMBus Host is communicating with Battery 1.
(Power On Reset Value)
To change this nibble, set only one of the lower two bits
of this nibble high. All other values will simply be ignored.
POWER_BY_BAT[4:1] Nibble
The read only POWER_BY_BAT[4:1] nibble is used by the
SMBus Host to determine which batteries are powering
the system. All writes to this nibble will be ignored.
Allowed values are:
0011b: System powered by both Battery 2 and Battery 1
simultaneously.
0010b: System powered by Battery 2 only.
0001b: System powered by Battery 1 only.
0000b: System powered by AC adapter only.
