MAX1645-MAX1645A Maxim, MAX1645-MAX1645A Datasheet - Page 27

• Manufacturer Part Number: MAX1645-MAX1645A
• Description: Advanced Chemistry-Independent / Level 2 Battery Chargers with Input Current Limiting
• Manufacturer: Maxim

case, it is the responsibility of the battery pack to manip-
ulate the resistance to obtain correct charger behavior.
The MAX1645/MAX1645A can drive two P-channel
MOSFETs to eliminate voltage drops across the
Schottky diodes, which are normally used to switch the
load current from the battery to the main DC source:
• The source switch P1 is controlled by PDS. This P-
• The load switch P2 is controlled by PDL. This P-
The MAX1645/MAX1645A have a 99.99% duty-cycle
capability with a 10ms maximum on-time and 1µs off-
Figure 10. Typical Single Smart Battery System
channel MOSFET is turned on when CVS rises to
300mV above BATT and turns off when CVS falls to
100mV above BATT. The same signal that controls
the PDS also sets the POWER_FAIL bit in the
Charger Status() register. See Operating Conditions.
channel MOSFET is turned off when the CVS rises to
100mV below BATT and turns on when CVS falls to
300mV below BATT.
Battery Chargers with Input Current Limiting
Advanced Chemistry-Independent, Level 2
Load and Source Switch Drivers
______________________________________________________________________________________
(SMBus HOST)
SYSTEM HOST
+12V, -12V
BATTERY DATA/STATUS REQUESTS
V
CC
Dropout Operation
CRITICAL EVENTS
SYSTEM
POWER
SUPPLY
DC (UNREGULATED) / V
BATTERY
SMART
CHARGING VOLTAGE/CURRENT
CRITICAL EVENTS
BATTERY
time. This allows the charger to achieve dropout perfor-
mance limited only by resistive losses in the DC-DC
converter components (P1, R1, N1, R2; see Figure 1).
The actual dropout voltage is limited to 300mV between
CVS and BATT by the power-fail comparator (see
Operating Conditions).
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
REQUESTS
V
SAFETY
SIGNAL
BATTERY
SMART BATTERY
System/Background Information
CONTROL
MAX1645A
SYSTEM
POWER
CHARGER
Applications Information
DC (UNREGULATED)
Smart Battery Charging
SMBus
(UNREGULATED)
CONVERTER
AC-DC
AC
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