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Keywords: efficiency, battery charger, battery mode, charge source
APPLICATION NOTE 5967
EFFICIENCY IMPROVEMENT IN BATTERY
MODE - MAX1737, MAX1757, MAX1758
By: Budge Ing
Abstract: This application note presents an efficiency improvement to the MAX1737, MAX1757, and
MAX1758 in battery mode when the charge source is removed.
The MAX1737, MAX1757, and MAX1758 are battery chargers for one to four cells (Figure 1). The devices
use the body diode of the internal MOSFET to provide load current when the charge source is removed.
The internal body diode voltage drop is ~700mV with 1A of load current. The maximum package dissipation
of the MAX1737 is 860mW and that of the MAX1757/MAX1758 is 762mW. Relying on the body diode of the
internal MOSFET when the battery provides the load current in the absence of a charger is not an
acceptable solution.
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