LTC4100 datasheet(17/48 Pages) LINER

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LTC1760

1760fa

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 configura-

tion 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.

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