Suitable Data Format
The circuit of the TSOP18..QJ1 is designed in that way
that unexpected output pulses due to noise or
disturbance signals are avoided. A bandpassfilter, an
integrator stage and an automatic gain control are
used to suppress such disturbances.
The distinguishing mark between data signal ( not
suppressed) and disturbance signal (supressed) are
carrier frequency, burst length and Signal Gap Time
(see diagram below).
The data signal should fullfill the following condition:
• Carrier frequency should be close to center fre-
quency of the bandpass (e.g. 38kHz).
• Burst length should be 6 cycles/burst or longer.
• After each burst a gap time of at least 9 cycles is
• The data format should not make a continuous
signal transmission. There must be a Signal Gap Time
(longer than 15ms) at least each 90ms (see Figure A)
Some examples for suitable data format are:
NEC Code (repetitive pulse), NEC Code (repetitive
data), Toshiba Micom Format, Sharp Code, RC5
Code, RECS–80 Code, R–2000 Code.
When a disturbance signal is applied to the
TSOP18..QJ1 it can still receive the data signal.
However the sensitivity is reduced to that level that no
unexpected pulses will occure.
Some examples for such disturbance signals which
are suppressed by the TSOP18..QJ1 are:
• DC light (e.g. from tungsten bulb or sunlight),
• Continuous signal at 38kHz or at any other
• Signals from fluorescent lamps (see Figure B)
• Continuous IR signal (e.g. 1ms burst, 2ms pause)
Signal Gap Time
0 10 20 30 40 50 60 70 80 90 100
Figure A: Data Signal (Output of IR Receiver) with a Signal Gap Time of 20ms
Signal Gap Time
0 2 4 6 8 10 12 14 16 18 20
Figure B: Disturbance Signal from Fluorescent Lamp with Signal Gap Time of 7ms (suppressed by TSOP18..)
Document Number 82049
Rev. 4, 05-Jun-00
www.vishay.de • FaxBack +1-408-970-5600