UNDERVOLTAGE_DISCONNECT_SWITCH

Published:2009/7/17 2:32:00 Author:Jessie | From:SeekIC

In an effort to conserve energy, simple shutdown schemes are incorporated into many battery-operated circuits. Not all circuits lend themselves to direct control, however. Instead, the supply must be turned off by a switch. The LTC1477 high-side switch is designed for this purpose and includes short-circuit current limiting and thermal shutdown to guard against faulty loads. The figure shows the LTC1477 and LTC699 conjoined in an undervoltage disconnect application. The LTC699 microprocessor supervisor disables the LTC1477; hence, the load is disabled whenever the input voltage falls below 4.65 V. An external logic signal applied to the gate of Q1 can also disable the LTC1477. When enabled, the LTC1477 output ramps over a period of approximately 1 ms, thereby limiting the peak current in the load capacitor to 500 mA. This prevents glitches on the 5-V source line that might otherwise affect adjacent loads.



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