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LTC4100

4100fb

OPERATION

Input: The CHARGING_VOLTAGE is an unsigned 16-bit

integer specifying the requested charging voltage in mV.

The LTC4100 considers any value from 0x0001 through

0x049F the same as writing 0x0000. The following

table deﬁnes the maximum permissible value of CHARG-

ING_VOLTAGE that will not set the VOLTAGE_OR in the

ChargerStatus() function for a given value of RVLIM:

RVLIM

Maximum ChargingVoltage()

Short to GND

0x225F (8796mV)

10kΩ ±1%

0x332F (13100mV)

33kΩ ±1%

0x43FF (17404mV)

100kΩ ±1%

0x54CF (21708mV)

Open (or Short to VDD)

0x6D5F (27996mV)

AlarmWarning() (‘h16)

Description: The Smart Battery, acting as a bus master

device, sends the AlarmWarning() message to the LTC4100

to notify it that one or more alarm conditions exist. Alarm

indications are encoded as bit ﬁelds in the Battery’s Sta-

tus register, which is then sent to the LTC4100 by this

function.

Purpose: The LTC4100 will use the information sent by

this function to properly charge the battery. The LTC4100

will only respond to certain alarm bits. Writing to this

function does not necessarily cause an alarm condition

that inhibits battery charging.

• SMBus Protocol: Write Word.

Input: Only the OVER_CHARGED_ALARM, TERMINATE

_CHARGE_ALARM, reserved (0x2000), and OVER

_TEMP_ALARM bits are supported by the LTC4100.

Writing a one to any of these speciﬁed bits will inhibit

the charging by the LTC4100 and will set the ALARM_

INHIBITED bit in the ChargerStatus() function. The

TERMINATE_DISCHARGE_ALARM, REMAINING_

CAPACITY_ALARM, REMAINING_TIME_ALARM, and the

ERROR bits are ignored by the LTC4100.

LTC0() (‘h3C)

Description: The SMBus Host uses this command to

determine the version number of the LTC4100 and set

extended operation modes not deﬁned by the Smart Bat-

tery Charger Speciﬁcation.

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 address

0x18 if the SMBALERT signal is actively pulling down the

SMBALERT# bus. The LTC4100 will follow the prioritiza-

tion reporting as deﬁned in the System Management Bus

Speciﬁcation, Version 1.1, from the SBS Implementers

Forum.

• SMBus Protocol: A 7-bit Addressable Device Responds

to an ARA.

Output: The Device Address will be sent to the SMBus

system host. The LTC4100 Device address is 0x12.

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.

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