HI-2579, HI-2581
threshold comparator that produces CMOS data at the
FUNCTIONAL DESCRIPTION
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.
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.
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.
Transmitter
MIL-STD-1553 Bus Interface
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.
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.
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. Alogic
“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
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) .
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 filter and
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING
CONDITIONS
Supply voltage (VDD)
-0.3 V to +5 V
-0.3 V DC to +3.6 V
50 Vp-p
VDD 3.3V ± 5%
Supply Voltage
Logic input voltage range
Receiver differential voltage
Driver peak output current
Power dissipation at 25°C
Solder Temperature
Temperature Range
Industrial Screening
Hi-Temp Screening
-40oC to +85oC
-55oC to +125oC
+1.0 A
1.0 W
245oC max.
175oC
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.
Junction Temperature
Storage Temperature
-65oC to +150oC
HOLT INTEGRATED CIRCUITS
4
HOLTIC [ HOLT INTEGRATED CIRCUITS ]
