Texas Instruments TMS3637P Data Manual Download

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6–1

6 Application Information

6.1

General Applications

In this section an example schematic is shown for each of the four transmission media categories for which
the device can be configured. These schematics help to define the capabilities of the TMS3637. When
configured for infrared, one transmitter works for both normal and modulated modes. In addition, a
recommended programming station is shown. The schematics are:

•

Direct-wired connection of transmitter/receiver
–

Two wires

–

Four wires

•

Infrared coupling of transmitter/receiver
–

Normal transmission mode

–

Modulated transmission mode

•

Radio frequency (RF) coupling of transmitter/receiver

•

RF receiver and decoder

•

Programming station used to program the TMS3637
–

6.2

Direct-Wire Connection of Transmitter and Receiver

The transmitter and receiver can be connected together by a direct two-wire or four-wire line. Both
configurations are described in the following paragraphs.

6.2.1

Two-Wire Direct Connection

Table 6–1 list the parts for the schematic of a two-wire direct connection of the transmitter and receiver
shown in Figure 6–1. Only two wires are required, primarily because the transmitted code is superimposed
on the source voltage delivered to the transmitter, and the transmitter uses its own internal oscillator. The
transmitter is configured as a normal continuous transmitter and the content of the configuration EEPROM
cells is:

The device uses its internal oscillator to clock the data out (transmitter) and clock data in (receiver). The
oscillating frequency of the transmitter is approximately 5.7 kHz. With V

= 5 V, the transmitted code on

OUT (point A) is a square waveform between 0 V (internal connection to GND) and 5 V. At point B, the
maximum value is 5 V (when OUT is open) and the minimum value is 4.8

10K/(10K+220) = 4.892 V (when

OUT is at 0 V). The voltage swing is then 5 V – 4.892 V = 108 mV. The voltage swing must not be much
greater than 100 mV because this is superimposed on the source voltage used to power the device. At point
C, the maximum value is V

/2 = 2.5 V and the minimum value is 2.5 V – 0.108 V = 2.4 V due to the coupling

through capacitor C2. At point D, R6 and C4 act as a low-pass filter (with a cutoff frequency of approximately
11 kHz) so that the code passes but higher frequency noise is suppressed. The receiver is configured as
an analog normal 1-code Q-state noninverting receiver and the content of the EEPROM cells is:

The receiver is used in the noninverting mode. Using OUT on the transmitter to transmit the code inverts
it, but the internal analog amplifier in the receiver (CF = 0) reinverts the signal. The signal path between the
transmitter and receiver does not invert the signal. The result is a signal that is noninverted at the internal
logic controller of the receiver, hence use CI = 0 for a noninverting receiver.

As required, the oscillating frequency of the receiver is about ten times greater than that of the 57 kHz
transmitter. This is easily set by keeping R

osc

constant but reducing C

osc

to one-tenth of its original value.

The signal on IN is internally amplified and the gain is calculated using equation 1:

)

32.5E6

103E-18

1.27E9

)

32.5E6

103E-18