T6B70AF

2002-02-28

3

Function Description

(1)

Pseudo sine wave generator and 4-bit DA converters (sending block)

Pseudo sine wave signal with Fosc/16 frequency is driven out from pseudo sine wave output pin

(SOUT+ and SOUT−).

The outputs of pins SOUT+ and SOUT− have the opposite polarities.

The block of pseudo sine wave generator and 4-bit DA converter (the side of SOUT+ pin) are shown

below.

The data of pseudo sine wave generator is driven out in the following sequence.

0 → 1 → 3 → 6 → 9 → C → E → F → F → E → C → 9 → 6 → 3 → 1 → 0 (in hexadecimal)

Thus, the pseudo sine waveform of positive-going and negative-going outputs is like a staircase at

no load.

An analog switch is incorporated so that the driver output buffer is connected to the transmission

line only when transmission is performed.

However, an emitter follower circuit is externally connected to the driver output buffer.

The phase difference between positive-going and negative-going outputs is within 180° ± 5°. (pseudo

sine wave output phase fluctuation)

FOSC

RST

MSB

R

R

R

R

R

R

R

R

LSB

SOUT+ pin

SOUT+

SOUT−

F

250 kHz

F

E

C

9

6

3

1

0

E

C

9

6

3

1 0

FSIN

@FOSC = 4 MHz