LTC1760 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1760' PDF : 44 Pages View PDF
LTC1760
OPERATION
2.6 LTC1760 SMBALERT Operation
The SMBALERT pin allows the LTC1760 to signal to the
SMBus Host that there has been a change of status.
This pin is asserted low whenever there is a change in
battery presence, AC presence or after a power on reset
event. This pin is cleared during an Alert Response or
any of the following reads:
BatterySystemState(),BatterySystemStateCont(), Bat-
terySystemInfo(), or LTC().
3 Charging Algorithm Overview
3.1 Wake-Up Charging Initiation
The following conditions must be met in order to allow
wake-up charging:
1. The battery thermistor must be COLD-RANGE, IDEAL-
RANGE, or UNDER-RANGE.
2. AC must be present.
3. BatterySystemStateCont(CHARGING_INHIBIT) must
be de-asserted (or low).
4. Hardware controlled charging inhibit must be
de-asserted (MODE not low with VDDS high). Refer to
“Section 6.2”.
Wake-up charging initiates when a newly inserted battery
does not respond to any LTC1760 Master read commands.
Only one battery will wake-up charge at a time. When two
batteries are inserted and both require wake-up charging,
Battery 1 will wake-up charge first. Battery 2 will only wake-
up charge when Battery 1 terminates wake-up charging.
Wake-up charging takes priority over controlled charg-
ing; this prevents one battery from tying up the charger
when it would be advantageous to dual charge two deeply
discharged batteries.
The LTC1760 will attempt to reinitiate wake-up
charging on both batteries after the SMBus Host asserts
BatterySystemStateCont(CHARGER_POR) or a power on
reset event. This will reset any wake-up charging safety
timers and is equivalent to removing and reinserting both
batteries.
The LTC1760 will attempt to reinitiate wake-up charging
on a battery if the battery is not being charged, the therm-
26
istor is reporting IDEAL-RANGE, and the battery fails to
respond to an SMBus query. This is an important feature
for handling deeply discharged NiMH batteries. These
batteries may begin to talk while being charged and go
silent once charging has stopped.
Wake-up charging is disabled if the battery thermistor is
COLD-RANGE or UNDER-RANGE and the battery has been
charged for longer than tTIMEOUT.
3.2 Wake-Up Charging Termination
The LTC1760 will terminate wake-up charging when any
of the following conditions are met:
1. Battery removal (thermistor indicating OVER-RANGE)
2. AC is removed.
3. The SMBus Host issues a calibration request by setting
BatterySystemStateCont(CALIBRATE) high.
4. Any response to an LTC1760 Master read of Charg-
ingCurrent(), Current(), ChargingVoltage(), or Voltage().
Note that the LTC1760 ignores all writes from the battery.
5. Any of the following AlarmWarning() bits asserted high:
OVER_CHARGED_ALARM
TERMINATE_CHARGE_ALARM
TERMINATE_CHARGE_RESERVED
OVER_TEMP_ALARM
Note that the LTC1760 ignores all writes from the battery.
Each battery’s charge alarm is cached inside the LTC1760.
This internally cached bit will be set when any of the up-
per four bits of the battery’s AlarmWarning() response
are set. The cached bit will remain set if a subsequent
AlarmWarning() fails to respond. The cached alarm will
be cleared by any of the following conditions.
a) Associated battery is removed.
b) A subsequent AlarmWarning() clears all
charge alarm bits for the associated battery.
c) A power on reset event.
d) The SMBus Host asserts
BatterySystemStateCont(CHARGER_POR) high.
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