| 摘要 |
A temperature limit circuit has a pair of comparators for producing an output signal when a sensed temperature either exceeds of falls below a permissible range. A common impedance circuit uses a single output pin to establish both the upper and lower temperature limits and a hysteresis level at each end of the range. A hysteresis circuit includes two branches, one of which directs a hysteresis current in one direction to a hysteresis resistor at a common input to the comparators to set the hysteresis at one end of the temperature range, and the other of which directs the hysteresis current through the hysteresis resistor in the opposite direction to set the hysteresis at the other end of the temperature range; the oppositely directed current flows establish hysteresis differentials of opposite polarities. A voltage reference circuit that includes a feedback circuit is preferably used for both temperature sensing and to establish a reference current upon which the hysteresis current is based. An isolation circuit emulates the feedback circuit and isolates the hysteresis current from the feedback current.
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