LTC4101 datasheet(14/28 Pages) LINER

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LTC4101

4101f

OPERATIO

The RES_UR bit is set only when the SafetySignal resis-

tance value is less than 575

Ω.

ALARM_INHIBITED bit is set if a valid AlarmWarning()

message has been received and charging is inhibited as a

result. This bit is cleared if both ChargingVoltage() and

ChargingCurrent() are rewritten to the LTC4101, power is

removed (DCDIV < VACP), or if a battery is removed. The

setting of the ALARM_INHIBITED will activate the LTC4101

SMBALERT pull-down.

POWER_FAIL bit is set if the LTC4101 does not have

sufficient DCIN voltage to charge the battery or if an

external device is pulling the CHGEN input signal low.

Charging is disabled whenever this bit is set. The setting

of this bit does not clear the values in the ChargingVoltage()

and ChargingCurrent() function values, nor does it neces-

sarily affect the charging modes of the LTC4101.

BATTERY_PRESENT is set if a battery is present otherwise

it is cleared. The LTC4101 uses the SafetySignal

in order to determine battery presence. If the LTC4101

detects a RES_OR condition, the BATTERY_PRESENT bit

is cleared immediately. The LTC4101 will not set the

BATTERY_PRESENT bit until it successfully samples the

SafetySignal twice and does not detect a RES_OR condi-

tion on either sampling. If AC is not present (e.g. DCDIV <

VACP), this bit may not be set for up to one-half second

after the battery is connected to the SafetySignal. The

ChargingCurrent() and ChargingVoltage() function values

are immediately cleared whenever this bit is cleared.

Charging will never be allowed if this bit is cleared. A

change in BATTERY_PRESENT will activate the LTC4101

SMBALERT pull-down.

AC_PRESENT is set if the voltage on DCDIV is greater than

VACP. This does not necessarily indicate that the voltage on

DCIN is sufficient to charge the battery. A change in

AC_PRESENT will activate the LTC4101 SMBALERT pull-

down.

ChargingCurrent() ('h14)

Description: The Battery, System Host or other master de-

vicesendsthedesiredchargingcurrent(mA)totheLTC4101.

Purpose: The LTC4101 uses RILIM, the granularity of the

IDAC, and the value of the ChargingCurrent() function to

determine its charging current supplied to the battery. The

charging current will never exceed the maximum current

permitted by RILIM. The ChargingCurrent() value will be

truncated to the granularity of the IDAC. The charging

current will also be reduced if the battery voltage exceeds

the programmed charging voltage.

• SMBus Protocol: Write Word.

Input: The CHARGING_CURRENT is an unsigned 16 bit

integer specifying the requested charging current in mA.

The following table defines the maximum permissible

value of CHARGING_CURRENT that will not set the

CURRENT_OR in the ChargerStatus() function for a given

value of the RILIM:

RILIM

ChargingCurrent()

Current

Short to GND

0x0000 through 0x03FF

0mA through 1023mA

10k

Ω ±1%

0x0000 through 0x07FF

0mA through 2047mA

33k

Ω ±1%

0x0000 through 0x0BFF

0mA through 3071mA

Open (or short to VDD) 0x0000 through 0x0FFF

0mA through 4095mA

ChargingVoltage() ('h15)

Description: The Battery, SMBus Host or other master

device sends the desired charging voltage (mV) to the

LTC4101.

Purpose: The LTC4101 uses RVLIM, the granularity of the

VDAC, and the value of the ChargingVoltage() function to

determine its charging voltage supplied to the battery. The

charging voltage will never be forced beyond the voltage

permitted by RVLIM. The ChargingVoltage() value will be

truncated to the granularity of the VDAC. The charging

voltage will also be reduced if the battery current exceeds

the programmed charging current.

• SMBus Protocol: Write Word.

Input: The CHARGING_VOLTAGE is an unsigned 16-bit

integer specifying the requested charging voltage in mV.

The LTC4101 considers any value from 0x0001 through

0x044F the same as writing 0x0000. The following

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