DS36C200M National Semiconductor, DS36C200M Datasheet - Page 6

• Manufacturer Part Number: DS36C200M
• Description: Dual High Speed Bi-Directional Differential Transceiver
• Manufacturer: National Semiconductor

www.national.com
Application Information
Receive Mode
IEEE 1394
The DS36C200 drives and receives IEEE 1394 physical
layer signal levels. The current mode driver is capable of
driving a 55
The DS36C200 is not designed to work with a link layer con-
troller IC requiring full 1394 physical layer compliancy to the
standard. No clock generator, no arbitration, and no encode/
decode logic is provided with this device. For a 1394 link
where speed sensing, bus arbitration, and other functions
are not required, a controller and the DS36C200 will provide
a cost effective, high speed dedicated link. This is shown in
Figure 10 . In applications that require fully compliant 1394
protocol, a link layer controller and physical layer controller
will be required as shown in Figure 10 . The physical layer
controller supports up to three DC36C200 devices (not
shown).
The DS36C200 drivers are current mode drivers and in-
tended to work with a two 110
allel with each other. The termination resistors should match
the characteristic impedance of the transmission media. The
drivers are current mode devices therefore the resistors are
required. Both resistors are required for half duplex opera-
tion and should be placed as close to the DO/RI+ and DO/
RI− pins as possible at opposite ends of the bus. However, if
your application only requires simplex operation, only one
termination resistor is required. In addition, note the voltage
levels will vary from those in the datasheet due to different
loading. Also, AC or unterminated configurations are not
used with this device. Multiple node configurations are pos-
6, 8, 9, 14
DE
L
L
L
L
10, 13
11, 12
10, 13
11, 12
Pin #
1, 7
1, 7
Input(s)
3
4
5
2
RE
H
L
L
L
load with V
*
(In mode only)
100 mV
Name
GND
OD
DO+
DO−
RE
V
RI+
RI−
RO
NC
DE
DI
CC
[RI+] − [RI−]
between 172 mV and 285 mV.
>
<
*
>
+100 mV
−100 mV
termination resistors in par-
Input/Output
&
X
>
−100 mV
(Continued)
Transmit and
Transmit
Receive
Receive
Mode
TABLE 1. Device Pin Descriptions
RO
H
L
X
Z
Driver Enable: When asserted low driver is disabled. And when
asserted high driver is enabled.
TTL/CMOS driver input pins
Non-inverting driver output pin
Inverting driver output pin
Receiver Enable: When asserted low receiver is enabled. And when
asserted high receiver is disabled.
Receiver output pin
Positive receiver input pin
Negative receiver input pin
Ground pin
Positive power supply pin, +5V
No Connect
6
Transmit Mode
H = Logic high level
L = Logic low level
X = Indeterminant state
Z = High impedance state
sible as long as transmission line effects are taken into ac-
count. Discontinuities are caused by mid-bus stubs, connec-
tors, and devices that affect signal integrity.
The differential line driver is a balanced current source de-
sign. A current mode driver, generally speaking has a high
output impedance and supplies a constant current for a
range of loads (a voltage mode driver on the other hand sup-
plies a constant voltage for a range of loads). Current is
switched through the load in one direction to produce a logic
state and in the other direction to produce the other logic
state. The typical output current is mere 3.8 mA, a minimum
of 3.1 mA, and a maximum of 5.2 mA. The current mode re-
quires that a resistive termination be employed to terminate
the signal and to complete the loop as shown in Figure 11 .
The 3.8 mA loop current will develop a differential voltage of
210 mV across the 55
ceiver detects with a 110 mV minimum differential noise mar-
gin neglecting resistive line losses (driven signal minus re-
ceiver threshold (210 mV – 100 mV = 110 mV)). The signal
is centered around +1.2V (Driver Offset, V
ground as shown in Figure 7 .
The current mode driver provides substantial benefits over
voltage mode drivers, such as an RS-422 driver. Its quies-
cent current remains relatively flat versus switching fre-
quency. Whereas the RS-422 voltage mode driver increases
exponentially in most case between 20 MHz–50 MHz. This
is due to the overlap current that flows between the rails of
the device when the internal gates switch. Whereas the cur-
rent mode driver switches a fixed current between its output
without any substantial overlap current. This is similar to
DE
H
H
H
L
Input(s)
RE
H
H
H
H
*
Description
±
2
10%
>
termination resistor which the re-
&
DI
H
X
L
>
0.8
Input/Output
OS
DO+
H
X
Z
L
) with respect to
DO−
H
X
Z
L