LTC4100 Linear Technology, LTC4100 Datasheet - Page 13

• Manufacturer Part Number: LTC4100
• Description: Smart Battery Charger Controller
• Manufacturer: Linear Technology

OPERATIO
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 I
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 I
is set, a less accurate I
the charging current, but because the charger is not
pulsed on and off, it may be preferred.
Output: The NO_LOWI indicates the I
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
The LTC Version Identification will always be 0x202 for the
LTC4100.
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 if the
SMBALERT signal is actively pulling down the SMBALERT#
bus. The LTC4100 will follow the prioritization reporting as
defined in the System Management Bus Specification,
Version 1.1, from the SBS Implementers Forum.
Output: The Device Address will be sent to the SMBus
system host. The LTC4100 Device address is 0x12 (or
0x09 if just looking at the 7-bit address field).
The following events will cause the LTC4100 to pull-down
the SMBALERT# bus through the SMBALERT pin:
Alert Response Address (ARA)
• SMBus Protocol: Write Word.
• SMBus Protocol: Read Word.
• SMBus Protocol: A 7-bit Addressable Device Re-
• Change of AC_PRESENT in the ChargerStatus() func-
sponds to an ARA.
tion.
DAC
value.
U
DAC
DAC
algorithm is used to generate
value. When the NO_LOWI
DAC
.
DAC
mode of opera-
SMBus Accelerator Pull-Ups
Both SCL and SDA have SMBus accelerator circuits which
reduce the rise time on systems with significant capaci-
tance 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 V
< V
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 I
pull-up circuits only pull to V
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 V
The Control Block
The LTC4100 charger operations are handled by the
control block. This block is capable of charging the se-
lected battery autonomously or under SMBus Host con-
trol. 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 LTC4100.
The control block receives SMBus slave commands from
the SMBus interface block.
The control block allows the LTC4100 to meet the follow-
ing Smart Battery-controlled (Level 2) charger
requirements:
1. Implements the Smart Battery’s critical warning mes-
2. Operates as an SMBus slave device that responds to
• Change of BATTERY_PRESENT in the ChargerStatus()
• Setting ALARM_INHIBITED in the ChargerStatus()
• Internal power-on reset condition.
sages over the SMBus.
ChargingVoltage() and ChargingCurrent() commands
and adjusts the charger output parameters accordingly.
DD
function.
function.
– 0.8V (external pull-up resistors are still required
2
C logic levels. Note that the dynamic
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when V
, so some SMBus devices
IN
LTC4100
> 0.8V until V
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13
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IN
.