HS-248RH Intersil Corporation, HS-248RH Datasheet - Page 3

• Manufacturer Part Number: HS-248RH
• Description: Rad-hard Triple Line Transmitter, Triple Line Receiver, Triple Party-line Receiver
• Manufacturer: Intersil Corporation

Test Circuits and Applications
Voltage Mode Transmission
Data rates of up to 10 million bits per second can be
obtained with standard TTL logic; however, the transmission
distance must be very short. For example, a typical 50 foot
low capacitance cable will have a capacitance of
approximately 750pF which requires a current of greater
than 50mA to drive 5V into this cable at 10MHz; therefore,
voltage mode transmitters are undesirable for long
transmission lines at high data rates due to the large current
required to charge the transmission line capacitance.
Current Mode Transmission
An alternate method of driving high data rates down long
transmission lines is to use a current mode transmitter.
Current mode logic changes the current in a low impedance
transmission line and requires very little change in voltage.
For example, a 2mA change in transmitter current will
produce a 100mV change in receiver voltage independent of
the series transmission line resistance. The rise time at the
receiver for a typical 50 foot cable (750pF) is approximately
30ns for a 2mA pulse.
NOTE: HS-245RH should be driven by open-collector
gates. (Totem-pole output may cause slight reduction in
“on” data current). For more detailed information, refer to
Design Information section of this data sheet.
IN
3
ENABLE
HS-245RH, HS-246RH, HS-248RH
(NOTE)
Design Information
(Continued)
FIGURE 3. TYPICAL APPLICATION
1/3
HS-245RH
+5V
An emitter coupled logic gate is frequently used for a current
mode transmitter. However, ECL gates are not compatible
with TTL and DTL logic and they require considerable
power. The Intersil HS-245RH is a TTL/DTL compatible
current mode transmitter designed for high data rates on
long transmission lines. Data rates of 15 megabits per
second can be obtained with 50 feet of transmission line
when using the companion HS-246RH receiver. Data rates
of 2 megabits per second are easily obtained on
transmission lines as long as 1,000 feet. The Intersil
transmitter and receivers feature very low power, typically
25mW for the transmitter and 15mW for the receiver.
Intersil Transmitter/Receivers
The Intersil transmitter/receiver family consists of a triple line
transmitter, two triple line receivers with internal terminations
and a triple party-line receiver. The general characteristics of
the transmitter and receivers are outlined in Table A.
(-)
(+)
1/3
HS-248RH
(+)
(-)
+5V
50Ω
50
Ω
“PARTY-LINE”
RECEIVER
+5V
-5V
1/3 HS-246RH
-5V
RECEIVER
OUT
OUTPUT