Figure 18. Typical Differential I/O Line Transmitter/Receiver And Terminators - Seagate Elite 9 Product Manual

Elite 9 Product Manual, Rev. C
11.7.3.2 Differential drivers and receivers
Typical differential driver and receiver circuits used by ST410800ND/WD
drives are shown in Figure 18.
Differential signals
All differential interface signals consist of two lines denoted +SIGNAL
and –SIGNAL. A signal is true when +SIGNAL is more positive than
–SIGNAL, and a signal is false when –SIGNAL is more positive than
+SIGNAL.
Output characteristics
Each signal driven by differential interface drives should have the following
output characteristics when measured at the disc drive's SCSI connector:
Low-level output voltage*
= 2.0V maximum at low-level output current
= 55 milliamps
High-level output voltage*
= 3.0V minimum at high-level output current
= −55 milliamps
Differential voltage
= 1.0V minimum with common-mode voltage ranges
from −7V DC to +12V DC
* Measure these voltages between the output terminal and the SCSI
device's logic ground reference.
The output characteristics must additionally conform to EIA RS-485-1983.
Input characteristics
Each signal received by differential interface drives should have the following
input characteristics when measured at the disc drive's SCSI connector:
Input current on either input
= +2.0 milliamps maximum
(includes receivers and passive drivers)
This requirement is met with the input voltage varying between −7V DC and
+12V DC, with power on or off, and with the hysteresis equaling 35 mV
minimum.
The input characteristics must additionally conform to EIA RS-485-1983.
+5V
5.6K
Transmit/Receive
Enable
Transmit or
Receive
Signal [2]

Figure 18. Typical differential I/O line transmitter/receiver and terminators

+5V
DE
LSI
[1]
XCVR
RE
1
1
R 2
[3]
[4]
57