PIN DESCRIPTIONS

FUNCTIONAL DESCRIPTION

The HI-1570 data bus transceiver contains differential volt-

age source drivers and differential receivers. They are in-

tended for applications using a MIL-STD-1553 A/B data

bus. The device produces a trapezoidal output waveform

during transmission.

Data input to the device’s transmitter section is from the

complementary CMOS / TTL inputs TXA/B and

/ .

The transmitter accepts Manchester II bi-phase data and

converts it to differential voltages on

.

The transceiver outputs are either direct or transformer cou-

pled to the MIL-STD-1553 data bus. Both coupling meth-

ods produce a nominal voltage on the bus of 7.5 volts peak

to peak at V

A&B = 5.0 Vdc. Refer to Figure 4 for

transmitter output amplitudes at other values of

A&B between 0 - 5 Vdc. (Contact your Holt Sales Repre-

sentative about the 0 - 10 Vdc Control Voltage option).

TRANSMITTER

TXA B

BUSA/B and

/

V

The transmitter is automatically inhibited and placed in the

high impedance state when both TXA/B and

/

are ei-

ther at a logic “1” or logic “0” simultaneously. A logic “1” ap-

plied to the TXINHA/B input will force the transmitter to the

high impedance state, regardless of the state of TXA/B and

/

BUSA B

TXA B

TXA B.

CONT

CONT

RECEIVER

The receiver accepts bi-phase differential data from the

MIL-STD-1553 bus through the same direct or transformer

coupled interface as the transmitter. The receiver’s differ-

ential input stage drives a filter and threshold comparator

that produces CMOS/TTL data at the RXA/B and

/

output pins.

RXA B

Each set of receiver outputs can be independently forced

to a logic "0" by setting RXENA or RXENB low.

A direct coupled interface (see Figure 2) uses a 1:2.5 ratio

isolation transformer and two 55 ohm isolation resistors

between the transformer and the bus.

In a transformer coupled interface (see Figure 3), the

transceiver is connected to a 1:1.79 isolation transformer

which in turn is connected to a 1:1.4 coupling transformer.

The transformer coupled method also requires two

coupling resistors equal to 75% of the bus characteristic

impedance (Zo) between the coupling transformer and the

bus.

MIL-STD-1553 BUS INTERFACE

PIN

SYMBOL

FUNCTION

DESCRIPTION

1

V

A/B

analog Input

Transmit output amplitude control (0 - 5 Vdc, see Figure 4)

2

BUSA

analog output

MIL-STD-1533 bus driver A, positive signal

3

analog output

MIL-STD-1553 bus driver A, negative signal

4

RXENA

digital input

Receiver A enable. If low, forces RXA and

low

5

GNDA

power supply

Ground for bus A

6

VDDA/B

7

BUSB

9

RXENB

10

GNDB

11

12

RXB

digital output

Receiver B output, non-inverted

13

TXINHB

digital input

Transmit inhibit, bus B. If high BUSB,

disabled

14

TXB

digital input

Transmitter B digital data input, non-inverted

15

digital input

Transmitter B digital data input, inverted

16

digital output

CONT

BUSA

RXA

BUSB

TXB

RXA

power supply

+5 volt power for both bus A and bus B

analog output

MIL-STD-1533 bus driver B, positive signal

8

analog output

MIL-STD-1553 bus driver B, negative signal

digital input

Receiver B enable. If low, forces RXB and

low

power supply

Ground for bus B

digital output

Receiver B output, inverted

Receiver A output, inverted

17

RXA

digital output

Receiver A output, non-inverted

18

TXINHA

digital input

Transmit inhibit, bus A. If high BUSA,

disabled

19

TXA

digital input

Transmitter A digital data input, non-inverted

20

digital input

Transmitter A digital data input, inverted

BUSB

RXB

RXB

BUSA

TXA

HI-1570

HOLT INTEGRATED CIRCUITS

2