MAX1644 Datasheet, PDF (27/32 Pages) Maxim Integrated Products – Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting

Advanced Chemistry-Independent, Level 2
Battery Charger with Input Current Limiting
VCC
+12V, -12V
SYSTEM
POWER
SUPPLY
DC (UNREGULATED) / VBATTERY
SYSTEM
POWER
CONTROL
AC
SYSTEM HOST
(SMBus HOST)
VBATTERY
DC (UNREGULATED)
AC-DC
CONVERTER
(UNREGULATED)
SMART
BATTERY
SAFETY
SIGNAL
MAX1645
SMART BATTERY
CHARGER
CRITICAL EVENTS
BATTERY DATA/STATUS REQUESTS
CHARGING VOLTAGE/CURRENT
REQUESTS
CRITICAL EVENTS
SMBus
Figure 10. Typical Single Smart Battery System
Applications Information
Smart Battery Charging
System/Background Information
A smart battery charging system, at a minimum, con-
sists of a smart battery and smart battery charger com-
patible with the Smart Battery System Specifications
using the SMBus.
A system may use one or more smart batteries. Figure 10
shows a single-battery system. This configuration is
typically found in notebook computers, video cameras,
cellular phones, or other portable electronic equipment.
Another configuration uses two or more smart batteries
(Figure 11). The smart battery selector is used either to
connect batteries to the smart battery charger or the
system, or to disconnect them, as appropriate. For
each battery, three connections must be made: power
(the battery’s positive and negative terminals), the
SMBus (clock and data), and the safety signal (resis-
tance, typically temperature dependent). Additionally,
the system host must be able to query any battery so it
can display the state of all batteries present in the system.
Figure 11 shows a two-battery system where battery 2
is being charged while battery 1 is powering the sys-
tem. This configuration may be used to “condition” bat-
tery 1, allowing it to be fully discharged prior to
recharge.
Smart Battery Charger Types
Two types of smart battery chargers are defined: Level 2
and Level 3. All smart battery chargers communicate
with the smart battery using the SMBus; the two types
differ in their SMBus communication mode and whether
they modify the charging algorithm of the smart battery
(Table 7). Level 3 smart battery chargers are supersets
of Level 2 chargers and, as such, support all Level 2
charger commands.
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