elleny

Provides +5V and +3.3V power to portable devices from USB port

Overview

The circuit shown in Figure 1 is powered by a universal serial bus (USB) port and can generate +5V and +3.3V power supplies to power portable devices such as digital cameras, MP3 players, and PDAs. The port is able to maintain normal communication while the power source is charging the Li+ battery. IC2 boosts the battery voltage (V _BATT ) to 5V, and IC3 steps down the 5V output to 3.3V.

Figure 1. This circuit is capable of generating +5V and +3.3V power for portable devices when powered through the USB port.

IC1 (Li+ battery charger) uses USB port power to charge the battery. Pull the SELI terminal low to set the charging current of 100mA, which is suitable for low-power USB ports; and set the SELI terminal high to set the charging current of 500mA, suitable for high-power USB ports. Similarly, setting SELV high or low configures the chip to charge a 4.2V or 4.1V Li+ battery. To protect the battery, IC1's final charging voltage is accurate to 0.5%. The /CHG terminal allows the chip to light the LED during charging.

Documentation

Application Note

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It is your responsibility to test the circuit yourself and determine its suitability for you. EEWorld will not be liable for direct, indirect, special, incidental, consequential or punitive damages arising from any cause or anything connected to any reference design used.

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Update:2025-06-20 14:28:19

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