鈥?/div>
Single PBC, CDR, Dual
Signal Detect (SD) in a
Single Package
鈥?Bidirectional, Symmetric
Bypass Capability
鈥?CDR in Bypass Path and
Loop Path
鈥?CDR Location Determined
by Wiring Configuration of
Pins on PCB (Patent
Pending)
鈥?Envelope Detect on Cable
Input (SD) for Both
Directions
鈥?Equalizers On All Inputs
鈥?High Speed PECL I/Os
Referenced to V
CC
鈥?Buffered Line Logic (BLL)
Outputs without External
Bias Resistors
鈥?0.4 W Typical Power at
V
CC
= 3.3 V
鈥?5 V Tolerant LVTTL I/O
鈥?24 Pin SSOP Package
HDMP-0421 Single
PBC & CDR
Description
The HDMP-0421 is a Single Port
Bypass Circuit (PBC) with Clock
and Data Recovery (CDR), and
dual Signal Detect (SD) capability.
This configuration will control
jitter accumulation while repeating
incoming signals. Port Bypass
Circuits are used to provide loops
that are continuously on in hard
disk arrays constructed in Fibre
Channel Arbitrated Loop (FC-AL)
configurations. Hard disks may be
pulled out or swapped while other
disks in the array are available to
the system. This device may also
be used in multi-initiator loop
configurations.
A Port Bypass Circuit is a 2:1
Multiplexer array with two modes
of operation: DISK IN LOOP and
DISK BYPASSED. In DISK IN
LOOP mode, the loop goes into
and out of the disk drive. Data go
from the HDMP-0421鈥檚
TO_NODE[n]鹵 differential output
pins to the Disk Drive Transceiver
IC (for example, an HDMP-1536A)
Rx鹵 differential input pins. Data
from the Disk Drive Transceiver
IC Tx鹵 differential output pins go
to the HDMP-0421鈥檚
FM_NODE[n]鹵 differential input
pins. Figures 4 and 5 show
connection diagrams for disk drive
array applications. In DISK
BYPASSED mode, the disk drive is
either absent or non-functional
and the loop bypasses the hard
disk. DISK IN LOOP mode is
enabled with a HIGH on the
BYPASS[n]鈥?pin and DISK
BYPASSED mode is enabled with a
LOW on the same pin.
Multiple HDMP-0421s may be
cascaded or connected to other
members of the HDMP-04xx
family through the FM_LOOP and
TO_LOOP pins to create loops for
arrays of disk drives. See Table 2
to identify which of the two cells
(0:1) will provide FM_LOOP,
TO_LOOP pins (cell connected to
cable). ALL TO_NODE outputs of
the HDMP-0421 are of equal
strength. Combinations of
HDMP-04xx may be utilized to
accommodate any number of hard
disks.
The HDMP-0421 may also be used
as a pair of 1=>1 buffers, one
with a CDR and another without.
For example, HDMP-0421 may be
placed in front of a CMOS ASIC to
clean the jitter of the outgoing
signal (CDR path) and to better
read the incoming signal (CDR-
less path).
Applications
鈥?RAID, JBOD Cabinets
鈥?1=>1 Gigabit Serial Buffer
Pair (with and w/o CDR)
鈥?Multi-Initiator Loops
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5
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9
10
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