LTC4100 datasheet(13/24 Pages) LINER

13 / 24 page

LTC4100

sn4100 4100is

OPERATIO

Purpose: This function allows the SMBus Host to deter-

mine if the battery charger is an LTC4100. Identifying the

manufacturer and version of the Smart Battery Charger

permits software to perform tasks specific to a given

charger. The LTC4100 also provides a means of disabling

the LOWI current mode of the IDAC.

• SMBus Protocol: Write Word.

Input: The NO_LOWI is the only bit recognized by this

function. The default value of NO_LOWI is zero. The

LTC4100 LOWI current mode provides a more accurate

average charge current when the charge current is less

than 1/16 of the full-scale IDAC value. When the NO_LOWI

is set, a less accurate IDAC algorithm is used to generate

the charging current, but because the charger is not

pulsed on and off, it may be preferred.

• SMBus Protocol: Read Word.

Output: The NO_LOWI indicates the IDAC mode of opera-

tion. If clear, then the LOWI current mode will be used

when the charging current is less than 1/16 of the full-

scale IDAC value.

The LTC Version Identification will always be 0x202 for the

LTC4100.

Alert Response Address (ARA)

Description: The SMBus system host uses the Alert

Response Address to quickly identify the generator of an

SMBALERT# event.

Purpose: The LTC4100 will respond to an ARA if the

SMBALERT signal is actively pulling down the SMBALERT#

bus. The LTC4100 will follow the prioritization reporting as

defined in the System Management Bus Specification,

Version 1.1, from the SBS Implementers Forum.

• SMBus Protocol: A 7-bit Addressable Device Re-

sponds to an ARA.

Output: The Device Address will be sent to the SMBus

system host. The LTC4100 Device address is 0x12 (or

0x09 if just looking at the 7-bit address field).

The following events will cause the LTC4100 to pull-down

the SMBALERT# bus through the SMBALERT pin:

• Change of AC_PRESENT in the ChargerStatus() func-

tion.

• Change of BATTERY_PRESENT in the ChargerStatus()

function.

• Setting ALARM_INHIBITED in the ChargerStatus()

function.

• Internal power-on reset condition.

SMBus Accelerator Pull-Ups

Both SCL and SDA have SMBus accelerator circuits which

reduce the rise time on systems with significant capaci-

tance on the two SMBus signals. The dynamic pull-up

circuitry detects a rising edge on SDA or SCL and applies

1mA to 10mA pull-up to VDD when VIN > 0.8V until VIN

< VDD – 0.8V (external pull-up resistors are still required

to supply DC current). This action allows the bus to meet

SMBus rise time requirements with as much as 250pF on

each SMBus signal. The improved rise time will benefit all

of the devices which use the SMBus, especially those

devices that use the I2C logic levels. Note that the dynamic

pull-up circuits only pull to VDD, so some SMBus devices

that are not compliant to the SMBus specifications may

still have rise time compliance problems if the SMBus pull-

up resistors are terminated with voltages higher than VDD.

The Control Block

The LTC4100 charger operations are handled by the

control block. This block is capable of charging the se-

lected battery autonomously or under SMBus Host con-

trol. The control block can request communications with

the system management host (SMBus Host) by asserting

SMBALERT = 0; this will cause the SMBus Host, if present,

to poll the LTC4100.

The control block receives SMBus slave commands from

the SMBus interface block.

The control block allows the LTC4100 to meet the follow-

ing Smart Battery-controlled (Level 2) charger

requirements:

1. Implements the Smart Battery’s critical warning mes-

sages over the SMBus.

2. Operates as an SMBus slave device that responds to

ChargingVoltage() and ChargingCurrent() commands

and adjusts the charger output parameters accordingly.

LTC4100 数据表(PDF) 13 Page - Linear Technology

LTC4100 数据表(HTML) 13 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

数据表下载