DS92LV1023 and DS92LV1224
40-66 MHz 10 Bit Bus LVDS Serializer and Deserializer
General Description
The
DS92LV1023
transforms
a
10-bit
wide
parallel
LVCMOS/LVTTL data bus into a single high speed Bus
LVDS serial data stream with embedded clock. The
DS92LV1224 receives the Bus LVDS serial data stream and
transforms it back into a 10-bit wide parallel data bus and
recovers parallel clock. The DS92LV1023 transmits data
over backplanes or cable. The single differential pair data
path makes PCB design easier. In addition, the reduced
cable, PCB trace count, and connector size tremendously
reduce cost. Since one output transmits clock and data bits
serially, it eliminates clock-to-data and data-to-data skew.
The powerdown pin saves power by reducing supply current
when not using either device. Upon power up of the Serial-
izer, you can choose to activate synchronization mode or
allow
the
Deserializer
to
use
the
synchronization-to-random-data feature. By using the syn-
chronization mode, the Deserializer will establish lock to a
signal within specified lock times. In addition, the embedded
clock guarantees a transition on the bus every 12-bit cycle.
This eliminates transmission errors due to charged cable
conditions. Furthermore, you may put the DS92LV1023 out-
put pins into TRI-STATE
to achieve a high impedance
state. The PLL can lock to frequencies between 40 MHz and
66 MHz.
Features
n
Clock recovery from PLL lock to random data patterns.
n
Guaranteed transition every data transfer cycle
n
Chipset (Tx + Rx) power consumption
<
500 mW (typ)
@
66 MHz
n
Single differential pair eliminates multi-channel skew
n
Flow-through pinout for easy PCB layout
n
660 Mbps serial Bus LVDS data rate (at 66 MHz clock)
n
10-bit parallel interface for 1 byte data plus 2 control bits
n
Synchronization mode and LOCK indicator
n
Programmable edge trigger on clock
n
High impedance on receiver inputs when power is off
n
Bus LVDS serial output rated for 27
load
n
Small 28-lead SSOP package
Block Diagrams
10093301
TRI-STATE
is a registered trademark of National Semiconductor Corporation.
June 2002
DS92L
V1023
and
DS92L
V1224
40-66
MHz
10
Bit
Bus
L
VDS
Serializer
and
Deserializer
2002 National Semiconductor Corporation
DS100933
www.national.com
Block Diagrams
(Continued)
Application
10093302
Functional Description
The DS92LV1023 and DS92LV1224 are a 10-bit Serializer
and Deserializer chipset designed to transmit data over dif-
ferential backplanes at clock speeds from 40 to 66 MHz. The
chipset is also capable of driving data over Unshielded
Twisted Pair (UTP) cable.
The chipset has three active states of operation: Initializa-
tion, Data Transfer, and Resynchronization; and two passive
states: Powerdown and TRI-STATE
.
The following sections describe each operation and passive
state.
Initialization
Initialization of both devices must occur before data trans-
mission begins. Initialization refers to synchronization of the
Serializer and Deserializer PLL's to local clocks, which may
be the same or separate. Afterwards, synchronization of the
Deserializer to Serializer occurs.
Step 1: When you apply V
CC
to both Serializer and/or Dese-
rializer, the respective outputs enter TRI-STATE
, and
on-chip power-on circuitry disables internal circuitry. When
V
CC
reaches V
CC
OK (2.5V) the PLL in each device begins
locking to a local clock. For the Serializer, the local clock is
the transmit clock (TCLK) provided by the source ASIC or
other device. For the Deserializer, you must apply a local
clock to the REFCLK pin.
The Serializer outputs remain in TRI-STATE while the PLL
locks to the TCLK. After locking to TCLK, the Serializer is
now ready to send data or SYNC patterns, depending on the
levels of the SYNC1 and SYNC2 inputs or a data stream.
The SYNC pattern sent by the Serializer consists of six ones
and six zeros switching at the input clock rate.
Note that the Deserializer LOCK output will remain high
while its PLL locks to the incoming data or to SYNC patterns
on the input.
Step 2: The Deserializer PLL must synchronize to the Seri-
alizer to complete initialization. The Deserializer will lock to
non-repetitive data patterns. However, the transmission of
SYNC patterns enables the Deserializer to lock to the Seri-
alizer signal within a specified time. See Figure 9.
The user's application determines control of the SYNC1 and
SYNC 2 pins. One recommendation is a direct feedback loop
from the LOCK pin. Under all circumstances, the Serializer
stops sending SYNC patterns after both SYNC inputs return
low.
When the Deserializer detects edge transitions at the Bus
LVDS input, it will attempt to lock to the embedded clock
information. When the Deserializer locks to the Bus LVDS
clock, the LOCK output will go low. When LOCK is low, the
Deserializer outputs represent incoming Bus LVDS data.
Data Transfer
After initialization, the Serializer will accept data from inputs
DIN0DIN9. The Serializer uses the TCLK input to latch
incoming Data. The TCLK_R/F pin selects which edge the
Serializer uses to strobe incoming data. TCLK_R/F high
selects the rising edge for clocking data and low selects the
falling edge. If either of the SYNC inputs is high for 5*TCLK
cycles, the data at DIN0-DIN9 is ignored regardless of clock
edge.
After determining which clock edge to use, a start and stop
bit, appended internally, frame the data bits in the register.
The start bit is always high and the stop bit is always low.
The start and stop bits function as the embedded clock bits
in the serial stream.
The Serializer transmits serialized data and clock bits (10+2
bits) from the serial data output (DO
) at 12 times the TCLK
frequency. For example, if TCLK is 66 MHz, the serial rate is
66 x 12 = 792 Mega-bits-per-second. Since only 10 bits are
from input data, the serial "payload" rate is 10 times the
TCLK frequency. For instance, if TCLK = 66 MHz, the pay-
load data rate is 66 x 10 = 660 Mbps. The data source
provides TCLK and must be in the range of 40 MHz to 66
MHz nominal.
The Serializer outputs (DO
) can drive a point-to-point con-
nection or in limited multi-point or multi-drop backplanes.
The outputs transmit data when the enable pin (DEN) is
high, PWRDN = high, and SYNC1 and SYNC2 are low.
When DEN is driven low, the Serializer output pins will enter
TRI-STATE.
When the Deserializer synchronizes to the Serializer, the
LOCK pin is low. The Deserializer locks to the embedded
DS92L
V1023/DS92L
V1224
www.national.com
2
Data Transfer
(Continued)
clock and uses it to recover the serialized data. ROUT data
is valid when LOCK is low. Otherwise ROUT0ROUT9 is
invalid.
The ROUT0-ROUT9 pins use the RCLK pin as the reference
to data. The polarity of the RCLK edge is controlled by the
RCLK_R/F input. See Figure 13.
ROUT(0-9), LOCK and RCLK outputs will drive a maximum
of three CMOS input gates (15 pF load) with a 66 MHz clock.
Resynchronization
When the Deserializer PLL locks to the embedded clock
edge, the Deserializer LOCK pin asserts a low. If the Dese-
rializer loses lock, the LOCK pin output will go high and the
outputs (including RCLK) will enter TRI-STATE.
The user's system monitors the LOCK pin to detect a loss of
synchronization. Upon detection, the system can arrange to
pulse the Serializer SYNC1 or SYNC2 pin to resynchronize.
Multiple resynchronization approaches are possible. One
recommendation is to provide a feedback loop using the
LOCK pin itself to control the sync request of the Serializer
(SYNC1 or SYNC2). Dual SYNC pins are provided for mul-
tiple control in a multi-drop application. Sending sync pat-
terns for resynchronization is desirable when lock times
within a specific time are critical. However, the Deserializer
can lock to random data, which is discussed in the next
section.
Random Lock Initialization and
Resynchronization
The initialization and resynchronization methods described
in their respective sections are the fastest ways to establish
the link between the Serializer and Deserializer. However,
the DS92LV1224 can attain lock to a data stream without
requiring the Serializer to send special SYNC patterns. This
allows the DS92LV1224 to operate in "open-loop" applica-
tions. Equally important is the Deserializer's ability to support
hot insertion into a running backplane. In the open loop or
hot insertion case, we assume the data stream is essentially
random. Therefore, because lock time varies due to data
stream characteristics, we cannot possibly predict exact lock
time. However, please see Table 1 for some general random
lock times under specific conditions. The primary constraint
on the "random" lock time is the initial phase relation be-
tween the incoming data and the REFCLK when the Dese-
rializer powers up. As described in the next paragraph, the
data contained in the data stream can also affect lock time.
If a specific pattern is repetitive, the Deserializer could enter
"false lock" - falsely recognizing the data pattern as the
clocking bits. We refer to such a pattern as a repetitive
multi-transition, RMT. This occurs when more than one
Low-High transition takes place in a clock cycle over multiple
cycles. This occurs when any bit, except DIN 9, is held at a
low state and the adjacent bit is held high, creating a 0-1
transition. In the worst case, the Deserializer could become
locked to the data pattern rather than the clock. Circuitry
within the DS92LV1224 can detect that the possibility of
"false lock" exists. The circuitry accomplishes this by detect-
ing more than one potential position for clocking bits. Upon
detection, the circuitry will prevent the LOCK output from
becoming active until the potential "false lock" pattern
changes. The false lock detect circuitry expects the data will
eventually change, causing the Deserializer to lose lock to
the data pattern and then continue searching for clock bits in
the serial data stream. Graphical representations of RMT are
shown in Figure 1. Please note that RMT only applies to bits
DIN0-DIN8.
Powerdown
When no data transfer occurs, you can use the Powerdown
state. The Serializer and Deserializer use the Powerdown
state, a low power sleep mode, to reduce power consump-
tion. The Deserializer enters Powerdown when you drive
PWRDN and REN low. The Serializer enters Powerdown
when you drive PWRDN low. In Powerdown, the PLL stops
and the outputs enterTRI-STATE, which disables load cur-
rent and reduces supply current to the milliampere range. To
exit Powerdown, you must drive the PWRDN pin high.
Before valid data exchanges between the Serializer and
Deserializer, you must reinitialize and resynchronize the de-
vices to each other. Initialization of the Serializer takes 510
TCLK cycles. The Deserializer will initialize and assert LOCK
high until lock to the Bus LVDS clock occurs.
TRI-STATE
The Serializer enters TRI-STATE when the DEN pin is driven
low. This puts both driver output pins (DO+ and DO-) into
TRI-STATE. When you drive DEN high, the Serializer returns
to the previous state, as long as all other control pins remain
static (SYNC1, SYNC2, PWRDN, TCLK_R/F).
When you drive the REN pin low, the Deserializer enters
TRI-STATE.
Consequently,
the
receiver
output
pins
(ROUT0ROUT9) and RCLK will enter TRI-STATE. The
LOCK output remains active, reflecting the state of the PLL.
TABLE 1.
Random Lock Times for the DS92LV1224
40 MHz
66 MHz
Units
Maximum
26
18
S
Mean
4.5
3.0
S
Minimum
0.77
0.43
S
Conditions:
PRBS 2
15
, V
CC
= 3.3V
1) Difference in lock times are due to different starting points in the data
pattern with multiple parts.
DS92L
V1023/DS92L
V1224
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3
Ordering Information
NSID
Function
Package
DS92LV1023TMSA
Serializer
MSA28
DS92LV1224TMSA
Deserializer
MSA28
10093324
DIN0 Held Low-DIN1 Held High Creates an RMT Pattern
10093325
DIN4 Held Low-DIN5 Held High Creates an RMT Pattern
10093326
DIN8 Held Low-DIN9 Held High Creates an RMT Pattern
FIGURE 1. RMT Patterns Seen on the Bus LVDS Serial Output
DS92L
V1023/DS92L
V1224
www.national.com
4
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
)
-0.3V to +4V
LVCMOS/LVTTL Input
Voltage
-0.3V to (V
CC
+0.3V)
LVCMOS/LVTTL Output
Voltage
-0.3V to (V
CC
+0.3V)
Bus LVDS Receiver Input
Voltage
-0.3V to +3.9V
Bus LVDS Driver Output
Voltage
-0.3V to +3.9V
Bus LVDS Output Short
Circuit
Duration
10mS
Junction Temperature
+150C
Storage Temperature
-65C to +150C
Lead Temperature
(Soldering, 4 seconds)
+260C
Maximum Package Power Dissipation Capacity
@
25C Package:
28L SSOP
1.27 W
Package Derating:
28L SSOP
10.3 mW/C above
+25C
ja
97C/W
jc
27C/W
ESD Rating for
DS92LV1023
HBM (1.5kOhm, 100pF)
>
1kV
MM
>
250V
ESD Rating for
DS92LV1224
HBM (1.5kOhm, 100pF)
>
2kV
MM
>
250V
Recommended Operating
Conditions
Min
Nom
Max
Units
Supply Voltage (V
CC
)
3.0
3.3
3.6
V
Operating Free Air
Temperature (T
A
)
-40
+25
+85
C
Receiver Input Range
0
2.4
V
Supply Noise Voltage
(V
CC
)
100 mV
P-P
Electrical Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
SERIALIZER LVCMOS/LVTTL DC SPECIFICATIONS (apply to DIN0-9, TCLK, PWRDN, TCLK_R/F, SYNC1, SYNC2, DEN)
V
IH
High Level Input Voltage
2.0
V
CC
V
V
IL
Low Level Input Voltage
GND
0.8
V
V
CL
Input Clamp Voltage
I
CL
= -18 mA
-0.86
-1.5
V
I
IN
Input Current
V
IN
= 0V or 3.6V
-10
1
+10
A
DESERIALIZER LVCMOS/LVTTL DC SPECIFICATIONS (apply to pins PWRDN, RCLK_R/ F, REN, REFCLK = inputs; apply
to pins ROUT, RCLK, LOCK = outputs)
V
IH
High Level Input Voltage
2.0
V
CC
V
V
IL
Low Level Input Voltage
GND
0.8
V
V
CL
Input Clamp Voltage
I
CL
= -18 mA
-0.62
-1.5
V
I
IN
Input Current
V
IN
= 0V or 3.6V
-10
1
+15
A
V
OH
High Level Output Voltage
I
OH
= -9 mA
2.2
3.0
V
CC
V
V
OL
Low Level Output Voltage
I
OL
= 9 mA
GND
0.25
0.5
V
I
OS
Output Short Circuit Current
VOUT = 0V
-15
-47
-85
mA
I
OZ
TRI-STATE Output Current
PWRDN or REN = 0.8V, V
OUT
= 0V or VCC
-10
0.1
+10
A
SERIALIZER Bus LVDS DC SPECIFICATIONS (apply to pins DO+ and DO-)
V
OD
Output Differential Voltage
(DO+)(DO-)
RL = 27
, Figure 18
200
290
mV
V
OD
Output Differential Voltage
Unbalance
35
mV
V
OS
Offset Voltage
1.05
1.1
1.3
V
V
OS
Offset Voltage Unbalance
4.8
35
mV
DS92L
V1023/DS92L
V1224
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5
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