TSOP48..QJ1
Vishay Telefunken
3 (7)Rev. 4, 29-Mar 01 www.vishay.com
Document Number 82120
Suitable Data Format
The circuit of the TSOP48..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 and
disturbance signal are carrier frequency, burst length
and duty cycle.
The data signal should fullfill the following condition:
•Carrier frequency should be close to center
frequency of the bandpass (e.g. 38kHz).
•Burst length should be 10 cycles/burst or longer.
•After each burst which is between 10 cycles and 70
cycles a gap time of at least 14 cycles is necessary.
•For each burst which is longer than 1.8ms a
corresponding gap time is necessary at some time in
the data stream. This gap time should be at least 4
times longer than the burst.
•Up to 800 short bursts per second can be received
continuously.
Some examples for suitable data format are:
NEC Code, Toshiba Micom Format, Sharp Code, RC5
Code, RC6 Code, R–2000 Code.
When a disturbance signal is applied to the
TSOP48..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 TSOP48..QJ1 are:
•DC light (e.g. from tungsten bulb or sunlight)
•Continuous signal at 38kHz or at any other
frequency
•Signals from fluorescent lamps with electronic
ballast with high or low modulation (see Figure A or
Figure B).
0 5 10 15 20
time [ms]
Figure A: IR Signal from Fluorescent Lamp with low Modulation
0 5 10 15 20
time [s]
Figure B: IR Signal from Fluorescent Lamp with high Modulation