Suitable Data Format
The circuit of the TSOP21..UH1 is designed in that
way that unexpected output pulses due to noise or dis-
turbance 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 dis-
turbance signal are carrier frequency, burst length and
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 6 cycles/burst or longer.
• After each burst which is between 6 cycles and 70
cycles a gap time of at least 10 cycles is
• 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 have at
least same length as the burst.
• Up to 2200 short bursts per second can be received
Some examples for suitable data format are:
NEC Code, Toshiba Micom Format, Sharp Code, RC5
Code, RC6 Code, RCMM Code, R–2000 Code,
When a disturbance signal is applied to the
TSOP21..UH1 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 TSOP21..UH1 are:
• DC light (e.g. from tungsten bulb or sunlight)
• Continuous signal at 38kHz or at any other
• Signals from fluorescent lamps with electronic
ballast (an example of the signal modulation is
shown in the figure below).
0 5 10 15 20
IR Signal from Fluorescent Lamp with low Modulation
Document Number 82123
Rev. 5, 30-Mar-01