In normal fan operation, pulse trains are present at the SENSE pin. These pulses are used to calculate the fan RPM. The fan RPM data is used to detect a worn out, stalled, open or unconnected fan. An RPM level below the user-programmable threshold causes the TC664 to assert a logic low alert signal (FAULT). Thedefault value is 500RPM. The TC664 consumes only 0.3mA during operation and can also enter a low-power shutdown mode by setting the appropriate bit in the configuration register.