Datasheet

MAX1667
Chemistry-Independent,
Level 2 Smart Battery Charger
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Level 2 Smart Battery Charger
The Level 2 or “smart-battery-controlled” smart battery
charger interprets the smart battery’s critical warning
messages, and operates as an SMBus slave device
that responds to ChargingVoltage() and Charging-
Current() messages sent to it by a smart battery. The
charger is obliged to adjust its output characteristics in
direct response to the messages it receives from the
battery. In Level 2 charging, the smart battery is com-
pletely responsible for initiating communication and for
providing the charging algorithm to the charger. The
smart battery is in the best position to tell the smart bat-
tery charger how it needs to be charged. The charging
algorithm in the battery may request a static charge
condition or may choose to periodically adjust the
smart battery charger’s output to meet its present
needs. A Level 2 smart battery charger is truly chem-
istry independent, and since it is defined as an SMBus
slave device only, it is relatively inexpensive and easy
to implement.
Table 1. Charger Type by SMBus Mode
and Charge Algorithm Source
Level 3Level 3Slave/Master
Level 3Level 2
Modified from BatteryBattery
Slave Only
SMBus MODE
CHARGE ALGORITHM SOURCE
Note: Level 1 smart battery chargers are defined in the ver-
sion 0.95a specification. While they can correctly interpret
smart battery end-of-charge messages minimizing over-
charge, they do not provide truly chemistry-independent
charging. They are no longer defined by the Smart Battery
Charger specification and are explicitly not compliant with this
and subsequent Smart Battery Charger specifications.
AC-DC
CONVERTER
(UNREGULATED)
AC
DC (UNREGULATED) / V
BATTERY
NOTE: SB 1 POWERING SYSTEM
SB 2 CHARGING
V
CC
+12V, -12V
SYSTEM HOST
(SMBus HOST)
SMART BATTERY
SELECTOR
SMBus
SMBus
SMBus
SAFETY SIGNAL
V
CHARGE
V
BATT
SAFETY
SIGNAL
V
BATT
SAFETY
SIGNAL
SMART BATTERY 1
SMART BATTERY 2
CRITICAL EVENTS
BATTERY DATA/STATUS REQUESTS
SMART BATTERY
CHARGER
SMBus
MAX1667
SYSTEM
POWER
SUPPLY
Figure 4. Typical Multiple Smart Battery System