Aeroflex Circuit Technology

SCD4808 REV E 12/9/99

Plainview NY (516) 694-6700

2

inputs are held low or high, the

transmitter output becomes a high

impedance and is “removed” from

the line. In addition, an overriding

“INHIBIT" input provides for the

removal of the transmitter output

from the line. A logic “1” applied to

the “INHIBIT” takes priority over the

condition of the data inputs and

disables

the

transmitter.

(See

Transmitter

Logic

Waveforms,

Figure 1.)

The transmitter utilizes an active

filter to suppress harmonics above

1 MHz to meet Macair specifications

A-3818,

A-4905,

A-5232

and

A-5690. The transmitter may be

safely operated for an indefinite

period at 100% duty cycle into a

data bus short circuit (Pt. A-A’).

Receiver

The

Receiver

section

accepts

bi-phase differential data at the input

and produces two TTL signals at the

output. The outputs are DATA and

DATA, and represent positive and

negative excursions of the input

beyond a pre-determined threshold.

(See Receiver Logic Waveforms,

Figure 2.)

The internal threshold is nominally

set

to

detect

data

bus

signals

exceeding 1.10 Volts P-P and reject

signals less than 0.6 Volts P-P

when used with a 1:1 turns ratio

transformer. (See Figure 4 for

transformer

data

and

typical

connection.)

A low level at the Strobe input

inhibits

the

DATA

and

DATA

outputs.

DATA IN

DATA IN

INHIBIT

LINE TO LINE

OUTPUT

NOTES:

2. DATA and DATA inputs must be complementary waveforms or 50% duty cycle average, with no delays between them.

3. DATA and DATA must be in the same state during off time (both high or low).

Figure 1 – Transmitter Logic Waveforms

Figure 2 – Receiver Logic Waveforms

Note overlap

devices, the receiver outputs are swapped as shown by the dashed lines

level

LINE TO LINE

INPUT

DATA OUT

DATA OUT

1. Line to line waveforms illustrate Macair signals, MIL-STD-1553 signals are trapezoidal