HI-2579, HI-2581
HOLT INTEGRATED CIRCUITS
4
FUNCTIONAL DESCRIPTION
The HI-2579 family of data bus transceivers contains
differential voltage source drivers, differential receivers
and integrated transformers. They are intended for
applications using a MIL-STD-1553 A/B data bus.
Transmitter
Data is input to the device’s transmitter section from
the complementary CMOS inputs TXA/B and TXA/B.
The transmitter accepts Manchester II bi-phase data
and converts it to differential voltages which drive the
internal transformers on BUSA/B and BUSA/B. The
transformer outputs are either direct or transformer
coupled to the MIL-STD-1553 data bus. Both coupling
methods produce a nominal voltage on the main 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 either at a logic “1” or logic “0” simultaneously. A logic
“1” applied to the TXINHA/B input forces the transmitter
to the high impedance 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
transformer coupled interface as the transmitter. The
receiver’s differential input stage includes a lter and
threshold comparator that produces 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-2579 and logic “1” on HI-2581.
Each set of receiver outputs can also be independently
forced to the bus idle state (logic “0” on HI-2579 or logic
“1” on HI-2581) by setting RXENA or RXENB low.
MIL-STD-1553 Bus Interface
There are two ways of connecting to the MIL-STD-1553
bus, using a direct coupled interface or a transformer
coupled interface (see Figure 3).
A direct coupled interface uses the internal 1:2.5 ratio
isolation transformer and two 55Ω isolation resistors
between the transformer and the bus.
In a transformer coupled interface, the transceiver is
connected to the internal 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. The coupling transformer and coupling resistors
are commonly integrated in a single device known as a
stub coupler.
Figure 4 and Figure 5 show test circuits for measuring
electrical characteristics of both direct and transformer
coupled interfaces respectively (see “electrical
characteristics” on the following pages) .
ABSOLUTE MAXIMUM RATINGS
Supply voltage (VDD)-0.3 V to +5 V
Logic input voltage range -0.3 V DC to +3.6 V
Receiver differential voltage 50 Vp-p
Driver peak output current +1.0 A
Power dissipation at 25°C 1.0 W
Solder Temperature 245oC max.
Junction Temperature 175oC
Storage Temperature -65oC to +150oC
RECOMMENDED OPERATING
CONDITIONS
Supply Voltage VDD 3.3V ± 5%
Temperature Range
Industrial Screening
Hi-Temp Screening
-40oC to +85oC
-55oC to +125oC
NOTE: Stresses above absolute maximum ratings or outside
recommended operating conditions may cause permanent
damage to the device. These are stress ratings only. Operation
at the limits is not recommended.