LTC4101
15
4101fa
OPERATION
table defi nes the maximum permissible value of CHARG-
ING_VOLTAGE that will not set the VOLTAGE_OR in the
ChargerStatus() function for a given value of R
VLIM
:
R
ILIM
Maximum ChargingVoltage()
Short to GND 0x1090 (4240mV)
10k ±1% 0x10D0 (4304mV)
33k ±1% 0x1150 (4432mV)
100k ± 1% 0x11A0 (4512mV)
Open (or short to V
DD
) 0x1580 (5504mV)
AlarmWarning() ('h16)
Description: The Smart Battery, acting as a bus master
device, sends the AlarmWarning() message to the LTC4101
to notify it that one or more alarm conditions exist. Alarm
indications are encoded as bit fi elds in the Battery’s Status
register, which is then sent to the LTC4101 by this func-
tion.
Purpose: The LTC4101 will use the information sent by
this function to properly charge the battery. The LTC4101
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 LTC4101.
Writing a one to any of these specifi ed bits will inhibit
the charging by the LTC4101 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 LTC4101.
LTC0() ('h3C)
Description: The SMBus Host uses this command to
determine the version number of the LTC4101 and set
extended operation modes not defi ned by the Smart Bat-
tery Charger Specifi cation.
Purpose: This function allows the SMBus Host to deter-
mine if the battery charger is an LTC4101. Identifying the
manufacturer and version of the Smart Battery Charger
permits software to perform tasks specifi c to a given
charger. The LTC4101 also provides a means of disabling
the LOWI current mode of the I
DAC
.
• 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
LTC4101 LOWI current mode provides a more accurate
average charge current when the charge current is less
than 1/16 of the full-scale I
DAC
value. When the NO_LOWI
is set, a less accurate I
DAC
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 I
DAC
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 I
DAC
value.
The LTC Version Identifi cation will always be 0x4040 for
the LTC4101.
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 LTC4101 will respond to an ARA address
0x18 if the SMBALERT signal is actively pulling down the
SMBALERT# bus. The LTC4101 will follow the prioritiza-
tion reporting as defi ned in the System Management Bus
Specifi cation, 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 LTC4101 Device address is 0x12.
The following events will cause the LTC4101 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.
