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MAX1838：Dual USB Switch with Fault Blanking and Autoreset

The MAX1838 is a dual, current-limited USB switch with auxiliary input supply. Each switch meets all IEC specifications for USB ports and is guaranteed to supply 500mA from either of two input supplies. A control pin selects the power source from either the main or auxiliary supply. The MAX1838 has multiple protection features, including independent thermal-shutdown on each channel to limit junction temperature in case of a prolonged short or overload condition. The device has accurate internal current-limit and reverse-current protection to safeguard the input supply against overload. When powered from the auxiliary supply, the current limit on each channel is set independently with an external resistor. An autoreset feature latches the switch off if the output is shorted, thereby saving system power. When the short is removed, the switch automatically turns back on. Independent fault signals (active-low FAULTA and active-low FAULTB) notify the microprocessor (µP) that the internal current limit has been reached. A 20ms fault-blanking feature prevents the MAX1838 from issuing false alarms to the host during power-up or when hot-swapping into a capacitive load. The MAX1838 is available in a space-saving 16-pin QSOP. For other USB current-limited switches, refer to the MAX1693, MAX1694, MAX1812, and MAX1823.

Key Features Dual USB Switch with Auxiliary Input Autoreset from Fault Condition Guaranteed 500mA Load per Channel Programmable Current Limits on Auxiliary Inputs Reverse Current Protection Thermal Overload Protection Built-In 20ms Fault-Blanking 4V to 5.5V Range Independent FAULT Indicator Outputs

MAX1838: Typical Operating Circuit

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