TSOP38S..

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Vishay Semiconductors

Rev. 1.3, 13-Apr-2022

6

Document Number: 82723

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SUITABLE DATA FORMAT

This series is designed to suppress spurious output pulses

due to noise or disturbance signals. The devices can

distinguish data signals from noise due to differences in

frequency, burst length, and envelope duty cycle. The data

signal should be close to the device’s band-pass center

frequency (e.g. 40 kHz) and fulfill the conditions in the table

below.

When a data signal is applied to the product in the

presence of a disturbance, the sensitivity of the receiver is

automatically reduced by the AGC to insure that no spurious

pulses are present at the receiver’s output.

Some examples which are suppressed are:

• DC light (e.g. from tungsten bulbs sunlight)

• Continuous signals at any frequency

• Strongly or weakly modulated patterns from fluorescent

lamps with electronic ballasts (see Fig. 14 or Fig. 15).

Fig. 14 - IR Disturbance from Fluorescent Lamp

With Low Modulation

Fig. 15 - IR Disturbance from Fluorescent Lamp

With High Modulation

Note

• Best choice of AGC for some popular IR-codes:

- TSOP38S40: Sony 12 bit, 15 bit, and 20 bit IR-codes

- TSOP38S56: Cisco SA code

16920

10

100

1000

10000

0

1

2

3

4

5

6

7

0

5

10

15

20

Axis Title

Time (ms)

16921

10

100

1000

10000

-60

-40

-20

0

20

40

0

5

10

15

20

Axis Title

Time (ms)

TSOP38S..

Minimum burst length

10 cycles/burst

After each burst of length

a minimum gap time is required of

10 to 70 cycles

≥ 10 cycles

For bursts greater than

a minimum gap time in the data stream is needed of

70 cycles

> 10 x burst length

Maximum number of continuous short bursts/second

1800

Sony code

preferred

Cisco SA code

preferred

Suppression of interference from fluorescent lamps

Most common disturbance patterns are suppressed