I have implemented a comparator and LED indication circuit to detect 12V supply with-in range of +/- 300mV.
As in the valid window considered is 11.7V (lower limit) and 12.3V (upper limit). With this understanding I have implemented an separate LED individually on pin# 6 (ABOVE) and another on pin#1 (WITHIN).
The LED on pin#1 will glow when the detected voltage falls in Valid Window (11.7V to 12.3V) and when the voltage is ABOVE12.3V the LED on pin#6 will glow. As a supply to this IC, on pin#8, 12V continuously supply from DC adapter is provided and on pin#3, the input is from power supply board, that generates 12V, is provided.
The problem is the LEDs on both the pin is not glow and indicating the proper margins. I simulated the circuit on LT spice, with the same values of resistors on IC pins and verified the high/ low levels (12V_EX in this case) on pin#1 and pin#6 when Vin was applied such that, 11.7 <= Vin <=12.3
But when I am measuring and testing on actual PCB, this circuit is not giving correct results.
Please review it and let me know if I have missed out any implementation in it.