Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
Copyright © 2000
Rev. 1.0c, 2005-02-08
WWW.Microsemi .COM
LX5261
27-Line LVD SCSI Source/Sink Re
ulator
TM
®
BLOCK DIAGRAM
+
-
6
7
3
VTERM
1.3V
Reference
+
-
1.75V
Reference
+
-
0.75V
Reference
1.3V +/- 0.1V
1.75V +/- 0.05V
200mA source/sink
0.75V +/- 0.05V
200mA source/sink
2
4GND
DIFSENS
VOUT1
VOUT2
Figure 1 – LX5261 Block Diagram
APPLICATION INFORMATION
LVD SCSI with Resistor Stack
The LX5261 is used with a LVD resistor network (475Ω, 121Ω, 475Ω) to meet LVD SCSI performance. Connecting the top side of the
LVD resistor network to the 1.75V regulated output (V
REG1,
pin 6), and the bottom side of the LVD resistor network to the 0.75 regulated
output (V
REG2
, pin 3) provides the correct bias voltage, differential impedance, common mode differential impedance, and common mode
voltage required by the SPI-2 through SPI-4 SCSI specification (see Figure 2. below). The LX5261 is designed to drive up to 27 LVD
pairs.
6
3
+
-
+
-
1.75V +/- 0.05V
200mA source/sink
0.75V +/- 0.05V
200mA source/sink
VOUT1
VOUT2
475
1%
475
1%
121
1%
Ln-
Ln+
1 of 27
LVD Pairs
4.7uF
4.7uF
27
27
Common Mode Impedance
Differential Bias Voltage
Common Mode Voltage
Differential Impedance
112.9
107.3
237
1.25
100 to 110
100 to 125
100 to 300
1.2 to 1.3
Parameter
LX5261 SCSI Standard Units
ohm
mV
V
ohm
Figure 2 – LX5261 with LVD Resistor Stack
B
B
L
L
O
O
C
C
K
K
D
D
I
I
A
A
G
G
R
R
A
A
M
M
