Texas Instruments TMS3637P, Data Manual

Page: 36 / 53

6–4
Table 6–2. Four-Wire Direct Connection
DEVICE FUNCTION
U1 TMS3637 configured as a normal continuous logic transmitter
U2 TMS3637 configured as an analog normal (1-code) Q-state noninverting receiver
U3 Inverter (NOT gate) used as external clock
R1 Feedback resistor for U3
R2 Resistor on TIME that, in conjunction with C2, determines OUT pulse duration on U2.
R3 Resistor on OSCR that, in conjunction with C3, determines internal oscillator frequency of U2.
R4 Pullup resistor for transmitter OUT, which is an open-drain output
R5 Current-limiting resistor for D1
C1 Part of feedback circuit used to cause U3 to oscillate
C2 Capacitor on TIME that, in conjunction with R2, determines OUT pulse duration on U2.
C3 Capacitor on OSCC that, in conjunction with R3, determines internal oscillator frequency of U2.
D1 LED for indication of received code
OSCR OSCC TIME GND
C1
22 nF
VCC IN CEX OUT
U1 (transmitter)
R3
22 k
Ω
OSCR OSCC TIME GND
C3
220 pF
VCC IN CEX OUT
U2 (receiver)
R1
1.8 k
Ω
R2
1 M
Ω
C2
470 nF
GND
VCC
R5
220
Ω
D1
VCC
OUT
R4
100 k
Ω
Code
U3
74HC14
Clock
8 7 6 5
1 2 3 4
8 7 6 5
1 2 3 4
Figure 6–2. Four-Wire Direct Connection