LTC4100
14
4100fc
For more information www.linear.com/LTC4100
operaTion
The RES_COLD bit is set only when the SafetySignal
resistance value is greater than 28.5kΩ. The SafetySignal
indicates a cold battery. The RES_COLD bit will be set
whenever the RES_OR bit is set.
The RES_HOT bit is set only when the SafetySignal
resistance is less than 3150Ω, which indicates a hot battery.
The RES_HOT bit will be set whenever the RES_UR bit is set.
The RES_UR bit is set only when the SafetySignal resis
-
tance value is less than 575Ω.
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 LTC4100, power
is removed (DCDIV < V
ACP
), or if a battery is removed.
The setting of the ALARM_INHIBITED will activate the
LTC4100 SMBALERT pull-down.
POWER_FAIL bit is set if the LTC4100 does not have suf
-
ficient 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 necessarily
affect the charging modes of the LTC4100.
BATTERY_PRESENT is set if a battery is present other
-
wise it is cleared. The LTC4100 uses the SafetySignal
in
order to determine battery presence. If the LTC4100
detects
a RES_OR condition, the BATTERY_PRESENT
bit is cleared immediately. The LTC4100 will not set the
BATTERY_PRESENT bit until it successfully samples
the SafetySignal twice and does not detect a RES_OR
condition on either sampling. If AC is not present (e.g.
DCDIV < V
ACP
), 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 LTC4100
SMBALERT pull-down.
AC_PRESENT is set if the voltage on DCDIV is greater than
V
ACP
. This does not necessarily indicate that the voltage
on DCIN is sufficient to charge the battery. A change
in AC_PRESENT will activate the LTC4100 SMBALERT
pull-down.
ChargingCurrent() (‘h14)
Description: The Battery, System Host
or other master
device
sends the desired charging current (mA) to the
LTC4100 .
Purpose: The LTC4100 uses R
ILIM
, the granularity of the
I
DAC
, 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 R
ILIM
. The ChargingCurrent() value will be
truncated to the granularity of the I
DAC
. The charging cur-
rent 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 R
ILIM
:
R
ILIM
ChargingCurrent() Current
Short to GND 0x0000 through 0x03FF 0mA through 1023mA
10kΩ ±1% 0x0000 through 0x07FF 0mA through 2047mA
33kΩ ±1% 0x0000 through 0x0BFF 0mA through 3071mA
Open (or Short to V
DD
) 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
LTC4100.
Purpose: The LTC4100 uses R
VLIM
, the granularity of the
V
DAC
, 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 R
VLIM
. The ChargingVoltage() value will be
truncated to the granularity of the V
DAC
. 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.
