Datasheet LTC1980 (Analog Devices) - 9

LTC1980
U OPERATIO
The LTC1980 is an IC designed to provide a regulated (Figure 1). The unique bidirectional power converter to- voltage to a system load from an unregulated or regulated pology (Figure 2) accounts for much of the area savings. wall adapter, or from a battery and also charge a battery, A transformer based design allows the wall adapter volt- thereby providing an uninterruptable power source for the age to be less than or greater than the battery voltage. system. When the wall adapter is present it provides The LTC1980 includes a 300kHz DC/DC PWM converter power to the system load and, if needed, a portion of the that operates in two modes. The first mode is when the wall power can be used to simultaneously charge the battery. adapter is present and the LTC1980 is used to charge the If the wall adapter is removed, the LTC1980 uses the battery using a constant-current/constant-voltage charge battery as a power source to continue providing a regu- scheme. The second mode is when the wall adapter is lated output voltage to power the system. removed and the battery powers the LTC1980 and the Combining these two functions into a single IC reduces DC/DC converter generates a regulated output voltage. circuit area compared to presently available solutions
Existing Methods
CHARGE TERMINATION
Using the LTC1980
BATTERY FROM CHARGER WALL ADAPTER FROM WALL ADAPTER LTC1980-BASED POWER ROUTING POWER DESIGN TO SYSTEM LOAD LOW DROPOUT TO SYSTEM LOAD DC/DC CONVERTERS 1980 F01 REGULATOR DC/DC CONVERTERS PWM REGULATOR
Figure 1. Portable Power Systems
T1 WALL T1 Li-Ion • ADAPTER Li-Ion • BATTERY BATTERY BAT-FET • REG-FET BAT-FET • REG-FET SYSTEM LOAD SYSTEM LOAD DC/DC DC/DC CONVERTERS R CONVERTERS S RS ISENSE ISENSE LTC1980 LTC1980 1980 F02a 1980 F02a
(a) Battery Charger Mode (b) DC/DC Converter Mode (Wall Adapter Removed) Figure 2. LTC1980 Bidirectional Power Conversion
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