HI-1579, HI-1581
PIN DESCRIPTIONS
PIN
(DIP & SOIC)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
-
PIN
(QFN)
38, 39
40, 41
42, 43
2
3, 4, 5
6, 7
8, 9
10, 11
16
17, 18, 19
20
21
24
25
26
29
30
31
36
37
1, 12, 13, 14, 15
33, 34, 35, 44
SYMBOL
VDDA
BUSA
BUSA
RXENA
GNDA
VDDB
BUSB
BUSB
RXENB
GNDB
RXB
RXB
TXINHB
TXB
TXB
RXA
RXA
TXINHA
TXA
TXA
No
FUNCTION
power supply
analog
analog
digital input
power supply
power supply
analog
analog
digital input
power supply
digital output
digital output
digital input
digital input
digital input
digital output
digital output
digital input
digital input
digital input
-
DESCRIPTION
+3.3 volt power for transceiver A
MIL-STD-1533 bus driver A, positive signal
MIL-STD-1553 bus driver A, negative signal
Receiver A enable. If low, forces RXA and RXA low
Ground for transceiver A
+3.3 volt power for transceiver B
MIL-STD-1533 bus driver B, positive signal
MIL-STD-1553 bus driver B, negative signal
Receiver B enable. If low, forces RXB and RXB low
Ground for transceiver B
Receiver B output, inverted
Receiver B output, non-inverted
Transmit inhibit, bus B. If high BUSB, BUSB disabled
Transmitter B digital data input, non-inverted
Transmitter B digital data input, inverted
Receiver A output, inverted
Receiver A output, non-inverted
Transmit inhibit, bus A. If high BUSA, BUSA disabled
Transmitter A digital data input, non-inverted
Transmitter A digital data input, inverted
-
22, 23, 27, 28, 32 Connect
FUNCTIONAL DESCRIPTION
The HI-1579 family of dual data bus transceivers contains
differential voltage source drivers and differential receiv-
ers. It is intended for applications using a MIL-STD-1553
A/B data bus. The device produces a trapezoidal output
waveform during transmission.
TRANSMITTER
Data input to the device’s transmitter section is from the
complementary CMOS inputs TXA/B and TXA/B. The
transmitter accepts Manchester II bi-phase data and con-
verts it to differential voltages on BUSA/B and BUSA/B.
The transceiver outputs are either direct- or transformer-
coupled to the MIL-STD-1553 data bus. Both coupling
methods produce a nominal voltage on the bus of 7.5 volts
peak to peak.
The transmitter is automatically inhibited and placed in the
high impedance state when both TXA/B and TXA/B are
driven with the same logic state. A logic “1” applied to the
TXINHA/B input forces the transmitter to the high imped-
ance state, regardless of the state of TXA/B and TXA/B.
RECEIVER
The receiver accepts bi-phase differential data from the
MIL-STD-1553 bus through the same direct- or trans-
former- coupled interface as the transmitter. The re-
ceiver’s differential input stage drives a filter and threshold
comparator to produce CMOS data at the RXA/B and RXA/B
output pins. When the MIL-STD-1553 bus is idle and RXENA
or RXENB are high, RXA/B will be logic “0” on HI-1579 and
logic “1” on HI-1581.
The receiver outputs are forced to the bus idle state (logic "0”
for HI-1579 or logic “1” for HI-1581) when the RXENA or
RXENB is low.
MIL-STD-1553 BUS INTERFACE
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. The primary center-tap
of the isolation transformer must be connected to GND.
In a transformer-coupled interface (see Figure 2), the
transceiver is also connected to a 1:2.5 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.
Figure 3 and Figure 4 show test circuits for measuring
electrical characteristics of both direct- and transformer-
coupled interfaces respectively.
(See electrical
characteristics on the following pages).
HOLT INTEGRATED CIRCUITS
2
HOLTIC [ HOLT INTEGRATED CIRCUITS ]
