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Cheetah X15 Product Manual, Rev. C
The output characteristics shall additionally conform to EIA RS-485.
LVD Differential
Driver
Signal +
Signal —
LVD Differential
Driver
Signal +
Signal —
|V
| = .6V
0
Figure 24.
LVD output signals
Input characteristics
Each signal (Vs) received by LVD interface receiver circuits shall have the following input characteristics when
measured at the disk drive connector:
Steady state Low level output voltage* = 0.030 V = < V
Steady state High level output voltage* = –3.6 V = < V
Differential voltage = +0.30 V minimum with common-mode voltage ranges 0.700 V = < V
(X3T10/1142D revision 13, p. 152)
*These voltages shall be measured between the output terminal and the SCSI device's logic ground reference.
Input characteristics shall additionally conform to EIA RS-485-983.
Figure 25.
Typical SE-LVD alternative transmitter receiver circuits
9.7.1.1
Single-ended drivers/receivers
The maximum total cable length allowed with drives using single-ended I/O driver and receiver circuits
depends on several factors. Table 19 lists the maximum lengths allowed for different configurations of drive
usage. These values are from the SPI-3 document. All device I/O lines must have equal to or less than 25 pf
capacitance to ground, measured at the beginning of the stub.
1.55V
.95V
.95V
1.55V
VCCA
LVD Signal Drivers
Single
Ended
Circuitry
Receiver
Single
Ended
Ground
Driver
LVD Signal Drivers
Ground
Single Ended:
GND
LVD:
+Signal
—15ma
V
= True / Logic 1 / Assertion
0
+15ma
+15ma
V
= False / Logic 0 / Negation
0
—15ma
= < 3.6 V (signal negation/logic 0)
s
= < –0.030 V (signal assertion/logic 1)
s
VCCB
Single
Ended
Receiver
LVD
—Signal
—Signal
= < 1.800 V.
cm
Single
Ended
Negation
Driver
Single
Ended
Assertion
Driver
67
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