Delay ckt

[tewills]

I am designing a fan control circuit using a microchip TC670. This ciruict will reside in a 1U chassis for 8 fans. I have (1) ALM LED on the front panel. If a fan dies, the LED will light. The problem with the 670 is, it faults immediately until RESET. Since it takes a while to power up the motherboard, the chip senses fan failure immediately then faults. I need to delay the funciton of the chip for at few seconds to allow the computer to competely power up.

 

[Sebi]

Apply a capacitor to threshold pin. 0.5....10uF

 

[tewills]

Thanks Sebi, since there are (8) fans, I need to use (8) TC670.s Which means everything will be multiplied by the quantity of (8). Would that include the cap you recommended? Or should your cap suggestion be in parallel with the Threshold (or ground).

 

[Sebi]

Yes, between the threshold input and GND.