LTC1760_11 Datasheet, PDF (28/48 Pages) Linear Technology – Dual Smart Battery System Manager Available in 48-Lead TSSOP Package

LTC1760
OPERATION
This cached bit will remain set if a subsequent AlarmWarn-
ing() 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.
7. The SMBus Host asserts
BatterySystemStateCont(CHARGING_INHIBIT) high.
8. Hardware controlled charging inhibit is asserted (MODE
low with V_DDS high).
9. The SMBus of the battery being charged has stopped
acknowledging SMBus read commands for longer than
t_TIMEOUT.
10. The thermistor of the battery being charged indicates
HOT-RANGE.
11. Any SMBus communication line is grounded for longer
than t_QUERY.
12. BatterySystemStateCont(POWER_NOT_GOOD) is high.
13. The emergency turn-off feature has been asserted
using the DCDIV input pin.
Whenever changing conditions cause either battery to
stop charging, charging is stopped immediately for all
batteries and the voltage and current algorithms are reset
to zero. Charging is not resumed until all the conditions
for controlled charging are met.
3.6 Controlled Charging Current Programming
The LTC1760 uses a single charger stage to simultaneously
charge up to two batteries. The batteries are connected to
the charger using a charge MUX. The charge MUX allows
the total charger current to be shared by the two batteries
while preventing charge transfer between the batteries.
Refer to “Section 7.1” and “Section 7.2”.
When charging a single battery, the charging algorithm
attempts to adjust the current so as to match the reported
current with the requested current. The LTC1760 continu-
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ously adjusts the charging current by the difference between
the actual and requested currents.
When simultaneously charging two batteries, the charging
algorithm attempts to adjust the current so as to match
the reported current with the requested current in both
batteries. The LTC1760 calculates the difference between
the requested and actual current in both batteries and
uses the minimum of these differences to increment or
decrement the total charge current being provided by the
charging stage.
The charging algorithm will not allow the reported actual
current to exceed the requested current in either battery.
For this reason the most efficient charging occurs for
matched batteries at similar charge states.
Whenever changing conditions cause either battery to
stop charging, the current algorithm is reset to zero. The
programmed current is updated every t_QUERY.
There are additional safety restrictions that limit the total
output current of the charger. These are detailed in the
following three sub-sections.
3.6.1 Current Limits When Charging A Single Battery
The following additional limits are applied to the charg-
ing current algorithm described in 3.6 when charging a
single battery:
a) The programmed current cannot exceed the requested
current + I_LIMIT/32.
b) The programmed current cannot exceed I_LIMIT.
3.6.2 Current Limits When Charging Two Batteries
(TURBO Mode Disabled)
The following additional limits are applied to the charging
current algorithm described in 3.6 when charging two
batteries with turbo mode disabled:
a) The programmed current cannot exceed the maximum
of the two requested currents + I_LIMIT/32.
b) The programmed current cannot exceed I_LIMIT.
3.6.3 Current Limits When Charging Two Batteries
(TURBO Mode Enabled)
The following additional limits are applied to the charging
current algorithm described in 3.6 when charging two
batteries with turbo mode enabled:
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