33_5_V_from_two_to_three_cells

Published:2009/7/24 23:16:00 Author:Jessie | From:SeekIC

Figure 8－85 shows a MAX718 dual regulator connected to provide a maln 3.3-V/5-V output and an auxiliary 5-V/12-V output, with a 0.9-V to VOUT input range, and a start-up of 1.4 V Quiescent curren(VIN＝3 V）is 140 μA for the main 5-V output.and 500 μA with both outputs. The maximum load-current capability of the malnsupply is 400 mA and 120 mA for the auxiliary Supply.Figure 8-86 shows theefficiency curves,The circuit can generate 3.3 V and 5 V, 3.3 V, and 12 V, or 5 V and 12 V, depending on the state of the logic inputs at pms 3 and 4.Two regulatedoutput voltages are generated from one of three input-voltage Sources∶an ac/dc wall-cube adapter(7 V or 20 V), a maln two-cell or three-cell battery,or a backuplithium battery. The dotted-line connection at the top of L2, which Powers theauxiliary supply, is normallv hard-wired to the maln battery,but it can also beconnected to the maln output when Power comes from the ac wall adapter. The main switching regulator automatically shuts off to save the batteries when the ac/dc wall cube is plugged in, MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION,1994, P.11.



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