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64
The output characteristics shall additionally conform to EIA RS-485.
LVD Differential
Driver
Signal +
Signal –
LVD Differential
Driver
Signal +
Signal –
|V
| = .6V
0
Figure 20.
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 21.
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 17 lists the maximum lengths allowed for different configurations of drive
usage. These values are from the SPI-2 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
–15ma
.95V
+15ma
.95V
+15ma
1.55V
–15ma
VCCA
LVD Signal Drivers
Single
Ended
Circuitry
Receiver
Single
Ended
Ground
Driver
LVD Signal Drivers
Ground
Single Ended:
GND
LVD:
+Signal
Cheetah 36LP Product Manual, Rev. B
V
= True / Logic 1 / Assertion
0
V
= False / Logic 0 / Negation
0
= < 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
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