LTC4101 データシートの表示（PDF） - Linear Technology

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LTC4101

Smart Battery Charger Controller

Linear Technology 

LTC4101

OPERATION

SMBus Accelerator Pull-Ups

Both SCL and SDA have SMBus accelerator circuits

which reduce the rise time on systems with significant

capacitance 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 LTC4101 charger operations are handled by the con-

trol block. This block is capable of charging the selected

battery autonomously or under SMBus Host control.

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 LTC4101.

The control block receives SMBus slave commands from

the SMBus interface block.

The control block allows the LTC4101 to meet the fol-

lowing 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.

3. The host may control charging by disabling the Smart

Battery’s ability to transmit ChargingCurrent() and

ChargingVoltage() request functions and broadcast-

ing the charging commands to the LTC4101 over the

SMBus.

4. The LTC4101 will still respond to Smart Battery critical

warning messages without host intervention.

16

Wake-up Charging Mode

The following conditions must be met in order to allow

wake-up charging of the battery:

1. The SafetySignal must be RES_COLD, RES_IDEAL, or

RES_UR.

2. AC must be present. This is qualified by DCDIV > VACP.

Wake-up charging initiates when a newly inserted battery

does not send ChargingCurrent() and ChargingVoltage()

functions to the LTC4101.

The following conditions will terminate the Wake-up

Charging Mode.

1. A TTIMEOUT period is reached when the SafetySignal is

RES_COLD or RES_UR.

2. The SafetySignal is registering RES_OR.

3. The successful writing of the ChargingCurrent() AND

ChargingVoltage() function. The LTC4101 will proceed

to the controlled charging mode after these two func-

tions are written.

4. The SafetySignal is registering RES_HOT.

5. The AC power is no longer present. (DCDIV < VACP)

6. The ALARM_INHIBITED becomes set in the Charger-

Status() function.

7. The INHIBIT_CHARGE is set in the ChargerMode()

function.

8. The CHGEN pin is pulled low by an external device. The

LTC4101 will resume wake-up charging, if the CHGEN

pin is released by the external device. Toggling the

CHGEN pin will not reset the TTIMEOUT timer.

9. There is insufficient DCIN voltage to charge the battery.

The LTC4101 will resume wake-up charging when there

is sufficient DCIN voltage to charge the battery. This

condition will not reset the TTIMEOUT timer.

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