LSI/CSI UL ® APPLICATION NOTE 706 LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631) 271-0400 FAX (631) 271-0405 A3800 DC TOUCH CONTROL SWITCH WITH DELAYED OFF November 1998 Touching the Touch Plate initiates negative-going pulses at LS7539 - Pin 8 (OUT). This triggers the One-Shot causing 556 - Pin 9 (ONE-SHOT Output) to go high. The One-Shot Output (556-9) turns on Q1, resetting OUT (LS7539-8) to a high. At the end of the OneShot, the Touch Plate is ready to be activated again. +V + 1µF - 10M 1 2 DISCH THR R2C2 = +V CMOS 556 V DD DISCH t 1.1 R2 14 13 OUT 3 8 7 OUT V SS 6 CV 5 MODE CONT 4 +V THR 12 C2 RESET CV 11 LS7539 5 60Hz CLOCK SYNC 1 2 V DD TOUCH 4 3 OUT R1 C1 270K +V +V R1C1 = 1 1.4 X 60 6 TRIG RESET OUT 7 Vss 10 +V 9 8 TRIG 60Hz (556-5) 1K OUT (7539-8) Q1 1000pF, 1KV ONE-SHOT 51K 1000pF, 1KV TOUCH PLATE ONE-SHOT (556-9) 709-111198-1 t