DS90UR908Q
5 - 65 MHz 24-bit Color FPD-Link II to FPD-Link Converter
General Description
Features
The DS90UR908Q converts FPD-Link II to FPD Link. It translates a high-speed serialized interface with an embedded
clock over a single pair (FPD-Link II) to four LVDS data/control
streams and one LVDS clock pair (FPD-Link). This serial bus
scheme greatly eases system design by eliminating skew
problems between clock and data, reduces the number of
connector pins, reduces the interconnect size, weight, and
cost, and overall eases PCB layout. In addition, internal DC
balanced decoding is used to support AC-coupled interconnects.
The DS90UR908Q converter recovers the data (RGB) and
control signals and extracts the clock from a serial stream
(FPD-Link II). It is able to lock to the incoming data stream
without the use of a training sequence or special SYNC patterns and does not require a reference clock. A link status
(LOCK) output signal is provided.
Adjustable input equalization of the serial input stream provides compensation for transmission medium losses of the
cable and reduces the medium-induced deterministic jitter.
EMI is minimized by the use of low voltage differential signaling, output voltage level select feature, and additional output
spread spectrum generation.
With fewer wires to the physical interface of the display, FPDLink output with LVDS technology is ideal for high speed, low
power and low EMI data transfer.
The DS90UR908Q is offered in a 48-pin LLP package and is
specified over the automotive AEC-Q100 grade 2 temperature range of -40˚C to +105˚C.
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5 – 65 MHz support (140 Mbps to 1.82 Gbps Serial Link)
5-channel (4 data + 1 clock) FPD-Link driver outputs
AC Coupled STP Interconnect up to 10 meters in length
Integrated input termination
@ Speed link BIST Mode and reporting pin
Optional I2C compatible Serial Control Bus
RGB888 + VS, HS, DE support
Power down mode minimizes power dissipation
FAST random data lock; no reference clock required
Adjustable input receive equalization
LOCK (real time link status) reporting pin
Low EMI FPD-Link output
SSCG option for lower EMI
1.8V or 3.3V compatible I/O interface
Automotive grade product: AEC-Q100 Grade 2 qualified
>8kV HBM ESD tolerance
Backward compatible mode for operation with older
generation devices
Applications
■ Automotive Display for Navigation
■ Automotive Display for Entertainment
Applications Diagram
30105127
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
© 2010 National Semiconductor Corporation
301051
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DS90UR908Q 5 - 65 MHz 24-bit Color FPD-Link II to FPD-Link Converter
October 20, 2010
DS90UR908Q
DS90UR908Q Pin Diagram
30105119
Pin Descriptions
Pin Name
Pin #
I/O, Type
Description
FPD-Link II Input Interface
RIN+
40
I, LVDS
True input
The input must be AC coupled with a 100 nF capacitor. Internal termination.
RIN-
41
I, LVDS
Inverting input
The input must be AC coupled with a 100 nF capacitor. Internal termination.
CMF
42
I, Analog
Common-Mode Filter
VCM center-tap is a virtual ground which maybe ac-coupled to ground to increase receiver
common mode noise immunity. Recommended value is 4.7 μF or higher.
FPD-Link Output Interface
TxOUT[3:0]+
15,19, 21,
23
O, LVDS
True LVDS Data Output
TxOUT[3:0]-
16,20, 22,
24
O, LVDS
Inverting LVDS Data Output
TxCLKOUT+
17
O, LVDS
True LVDS Clock Output
TxCLKOUT-
18
O, LVDS
Inverting LVDS Clock Output
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2
Pin #
I/O, Type
Description
O, LVMOS
LOCK Status Output
LOCK = 1, PLL is locked, output states determined by OEN.
LOCK = 0, PLL is unlocked, output states determined by OSS_SEL and OEN. Table 3
May be used as a Link Status or to flag when the Video Data is active (ON/OFF).
LVCMOS Outputs
LOCK
27
Control and Configuration
PDB
1
I, LVCMOS
w/ pull-down
Power Down Mode Input
PDB = 1, Device is enabled (normal operation)
PDB = 0, Device is in power-down, the outputs are TRI-STATE. Control registers are
RESET.
VODSEL
33
I, LVCMOS
w/ pull-down
FPD-Link Output Voltage Select. Table 4
VODSEL = 1, LVDS VOD is ±400 mV, 800 mVp-p (typ)
VODSEL = 0, LVDS VOD is ±250 mV, 500 mVp-p (typ)
OEN
30
I, LVCMOS
w/ pull-down
Output Enable Input
Table 3
OSS_SEL
35
I, LVCMOS
w/ pull-down
Output Sleep State Select Input
See Table 3.
LFMODE
36
I, LVCMOS
w/ pull-down
Low Frequency Mode — Pin or Register Control
LF_MODE = 1, low frequency mode (TxCLKOUT = 5-20 MHz)
LF_MODE = 0, high frequency mode (TxCLKOUT = 20-65 MHz)
MAPSEL
34
I, LVCMOS
w/ pull-down
FPD-Link Map Select — Pin or Register Control
MAPSEL = 1, MSB on TxOUT3+/-, Figure 15
MAPSEL = 0, LSB on TxOUT3+/-, Figure 14
CONFIG[1:0]
11,10
I, LVCMOS
w/ pull-down
Operating Modes — Pin or Register Control
Determine the device operating mode and interfacing device. Table 1
CONFIG[1:0] = 00: Interfacing to DS90UR905Q or DS90UR907Q, Control Signal Filter
DISABLED
CONFIG[1:0] = 01: Interfacing to DS90UR905Q or DS90UR907Q, Control Signal Filter
ENABLED
CONFIG[1:0] = 01: Interfacing to DS90UR241 or DS99R421
CONFIG[1:0] = 11: Interfacing to DS90C241
SSC[2:0]
7, 2, 3
I, LVCMOS
w/ pull-down
Spread Spectrum Clock Generation (SSCG) Range Select
See Tables 5, 6
RES
37
I, LVCMOS
w/ pull-down
Reserved
Tie Low
Control and Configuration — STRAP PIN
For a High State, use a 10 kΩ pull up to VDDIO; for a Low State, the IO includes an internal pull down. The STRAP pin is read upon
power-up and set device configuration. Pin number listed along with shared LVCMOS Output name in square bracket.
EQ
28 [PASS]
STRAP
I, LVCMOS
w/ pull-down
EQ Gain Control of FPD-Link II Input
EQ = 1, EQ gain is enabled (~13 dB)
EQ = 0, EQ gain is disabled (~1.625 dB)
Optional BIST Mode
BISTEN
29
I, LVCMOS
w/ pull-down
BIST Enable Input – Optional
BISTEN = 1, BIST Mode is enabled.
BISTEN = 0, normal mode.
PASS
28
O, LVCMOS
PASS Output (BIST Mode) – Optional
PASS = 1, no errors detected
PASS = 0, errors detected
Leave open if unused. Route to a test point (pad) recommended.
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DS90UR908Q
Pin Name
DS90UR908Q
Pin Name
Pin #
I/O, Type
Description
Optional Serial Bus Control Interface
SCL
5
I, LVCMOS
Serial Control Bus Clock Input - Optional
SCL requires an external pull-up resistor to VDDIO.
SDA
4
I/O,
LVCMOS
Open Drain
Serial Control Bus Data Input / Output - Optional
SDA requires an external pull-up resistor to VDDIO.
ID[x]
12
I, Analog
Serial Control Bus Device ID Address Select — Optional
Resistor to Ground and 10 kΩ pull-up to 1.8V rail. See Table 7.
Power and Ground
VDDL
6, 31
Power
Logic Power, 1.8 V ±5%
VDDA
38, 43
Power
Analog Power, 1.8 V ±5%
VDDP
8
Power
PLL Power, 1.8 V ±5%
VDDSC
46, 47
Power
SSC Generator Power, 1.8 V ±5%
VDDTX
13
Power
FPD-Link Power, 3.3 V ±10%
VDDIO
25
Power
LVCMOS I/O Power, 1.8 V ±5% OR 3.3 V ±10%
GND
9, 14, 26,
32, 39, 44,
45, 48
Ground
Ground
DAP
DAP
Ground
DAP is the large metal contact at the bottom side, located at the center of the LLP package.
Connect to the ground plane (GND) with at least 9 vias.
NOTE: 1 = HIGH, 0 = LOW
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4
DS90UR908Q
Block Diagram
30105129
FPD-Link II to FPD-Link Convertor
Ordering Information
NSID
Package Description
Quantity
SPEC
Package ID
DS90UR908QSQE
48–pin LLP, 7.0 X 7.0 X 0.8 mm, 0.5 mm pitch
250
NOPB
SQA48A
DS90UR908QSQ
48–pin LLP, 7.0 X 7.0 X 0.8 mm, 0.5 mm pitch
1000
NOPB
SQA48A
DS90UR908QSQX
48–pin LLP, 7.0 X 7.0 X 0.8 mm, 0.5 mm pitch
2500
NOPB
SQA48A
Note: Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market,
including defect detection methodologies. Reliability qualification is compliant with the requirements and temperature grades
defined in the AEC Q100 standard. Automotive Grade products are identified with the letter Q. For more information go to
http://www.national.com/automotive.
5
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DS90UR908Q
ESD Rating (ISO10605), RD = 330Ω, CS = 150/330pF
ESD Rating (ISO10605), RD = 2kΩ, CS = 150/330pF
Air Discharge (RIN+, RIN−)
≥±15 kV
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 – VDDn (1.8V)
Supply Voltage – VDDTX (3.3V)
Supply Voltage – VDDIO
LVCMOS I/O Voltage
Receiver Input Voltage
LVDS Output Voltage
Junction Temperature
Storage Temperature
48L LLP Package
Maximum Power Dissipation
Capacity at 25°C
Derate above 25°C
θJA
1/ θJA°C/W
27.7 °C/W
θJC
3.0 °C/W
ESD Rating (CDM)
≥±1.25 kV
ESD Rating (HBM)
For soldering specifications:
see product folder at www.national.com and
www.national.com/ms/MS/MS-SOLDERING.pdf
Recommended Operating
Conditions
Supply Voltage (VDDn)
LVCMOS Supply
Voltage (VDDIO)
OR
LVCMOS Supply
Voltage (VDDIO)
Operating Free Air
Temperature (TA)
TxCLKOUT Frequency
Supply Noise (Note 8)
ESD Rating (IEC, powered-up only), RD = 330Ω, CS = 150pF
Air Discharge (RIN+, RIN−)
≥±15 kV
≥±8 kV
Contact Discharge (RIN+, RIN−)
ESD Rating (HBM)
≥±8 kV
≥±8 kV
≥±8 kV
Contact Discharge (RIN+, RIN−)
−0.3V to +2.5V
−0.3V to +4.0V
−0.3V to +4.0V
−0.3V to +(VDDIO + 0.3V)
−0.3V to (VDD + 0.3V)
−0.3V to (VDDTX + 0.3V)
+150°C
−65°C to +150°C
Min
1.71
1.71
Nom
1.8
1.8
Max
1.89
1.89
Units
V
V
3.0
3.3
3.6
V
−40
5
+25
+105
65
100
°C
MHz
mVP-P
DC Electrical Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Pin/Freq.
Min
Typ
Max
Units
VODSEL = L
100
250
400
mV
VODSEL = H
200
400
600
mV
FPD-Link LVDS Output
|VOD|
Differential Output Voltage
VODp-p
Differential Output Voltage
A-B
ΔVOD
Output Voltage Unbalance
RL = 100Ω
Figure 7
VOS
Offset Voltage
ΔVOS
Offset Voltage Unbalance
IOS
Output Short Circuit Current
Vout = GND
Output TRI-STATE® Current
OEN = GND,
Vout =VDDTX, or GND
IOZ
VODSEL = L
500
mVp-p
VODSEL = H
800
mVp-p
VODSEL = H TxCLKOUT+,
TxCLKOUT-,
VODSEL = L
TxOUT[3:0]+,
VODSEL = H TxOUT[3:0]-
1.0
4
50
mV
1.2
1.5
V
1.2
1
V
50
-5
mV
mA
-10
+10
µA
2.2
VDDIO
V
GND
0.8
V
+15
μA
3.3 V I/O LVCMOS DC SPECIFICATIONS – VDDIO = 3.0 to 3.6V
VIH
High Level Input Voltage
VIL
Low Level Input Voltage
IIN
Input Current
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PDB,
VODSEL,
OEN,
OSS_SEL,
MAPSEL,
LFMODE,
SSC[2:0],
BISTEN
VIN = 0V or VDDIO
6
-15
±1
Parameter
Conditions
VOH
High Level Output Voltage
IOH = −2 mA
VOL
Low Level Output Voltage
IOL = +2 mA
IOS
Output Short Circuit Current
VOUT = 0V
TRI-STATE® Output Current
PDB = 0V, OSS_SEL = 0V,
VOUT = 0V or VDDIO
IOZ
Pin/Freq.
Min
Typ
VDDIO0.25
VDDIO
GND
LOCK, PASS
Max
Units
V
0.2
-45
V
mA
-10
+10
µA
0.7*
VDDIO
VDDIO
V
GND
0.3*
VDDIO
V
+10
μA
1.8 V I/O LVCMOS DC SPECIFICATIONS – VDDIO = 1.71 to 1.89V
VIH
High Level Input Voltage
VIL
Low Level Input Voltage
IIN
Input Current
VIN = 0V or VDDIO
VOH
High Level Output Voltage
IOH = −2 mA
VOL
Low Level Output Voltage
IOL = +2 mA
IOS
Output Short Circuit Current
VOUT = 0V
IOZ
TRI-STATE Output Current
VOUT = 0V or VDDIO
PDB,
VODSEL,
OEN,
OSS_SEL,
MAPSEL,
LFMODE,
SSC[2:0],
BISTEN
LOCK, PASS
-10
±1
VDDIO
- 0.2
VDDIO
GND
V
0.2
-13
-15
V
mA
+15
µA
+50
mV
FPD-Link II LVDS RECEIVER DC SPECIFICATIONS
VTH
Differential Input Threshold
High Voltage
VTL
Differential Input Threshold
Low Voltage
VCM
Common Mode Voltage,
Internal VBIAS
RT
Input Termination
VCM = +1.2V (Internal VBIAS)
RIN+, RIN-
-50
mV
1.2
80
V
100
120
Ω
85
95
mA
40
50
mA
0.3
0.8
mA
0.8
1.5
mA
SUPPLY CURRENT
IDD1
IDDTX1
IDDIO1
IDD2
IDDTX2
IDDIO2
Supply Current
(includes load current)
65 MHz Clock
Supply Current
(includes load current)
65 MHz Clock
All VDD(1.8)
VDDn= 1.89V
Checker Board
pins
Pattern, VODSEL = H V
=
3.6V
VDDTX
DDTX
SSC{2:0] = 000
VDDIO=1.89V
Figure 1
VDDIO
VDDIO = 3.6V
All VDD(1.8)
VDDn= 1.89V
Checker Board
pins
Pattern, VODSEL = H V
=
3.6V
VDDTX
DDTX
SSC[2:0] = 111
VDDIO=1.89V
Figure 1
VDDIO
VDDIO = 3.6V
IDDZ
IDDTXZ
IDDIOZ
VDD= 1.89V
Supply Current Power Down
PDB = 0V, All other
LVCMOS Inputs = 0V
All VDD(1.8)
pins
95
mA
40
mA
0.3
mA
0.8
mA
0.15
2.00
mA
VDDTX = 3.6V VDDTX
0.01
0.10
mA
VDDIO=1.89V VDDIO
0.01
0.08
mA
VDDIO = 3.6V
0.01
0.08
mA
7
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DS90UR908Q
Symbol
DS90UR908Q
Switching Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Pin/Freq.
Min
Typ
Max
Units
FPD-Link II
tDDLT
tIJIT
Lock Time
Figure 6
Input Jitter Tolerance
Figure 9
SSC[2:0] = 000
5 MHz
7
ms
SSC[2:0] = 111
5 MHz
14
ms
SSC[2:0] = 000
65 MHz
6
ms
SSC[2:0] = 111
65 MHz
8
ms
EQ = Off
SSC[2:0] = 000
TxCLKOUT± = 65 MHz
Input Jitter Frequency <
2 MHz
>0.9
UI
Input Jitter Frequency >
6 MHz
> 0.5
UI
RL = 100Ω
TxCLKOUT±,
TxOUT[3:0]±
FPD-Link Output
tTLHT
Low to High Transition Time
tTHLT
High to Low Transition Time
5 MHz
0.3
0.6
ns
0.3
0.6
ns
900
2100
ps
75
125
ps
tDCCJ
Cycle-to-Cycle Output Jitter
(Note 7, Note 9, Note 10)
tTTP1
Transmitter Pulse Position for
bit 1
1
UI
tTTP0
Transmitter Pulse Position for
bit 0
2
UI
tTPP6
Transmitter Pulse Position for
bit 6
3
UI
tTTP5
Transmitter Pulse Position for
bit 5
4
UI
tTTP4
Transmitter Pulse Position for
bit 4
5
UI
tTTP3
Transmitter Pulse Position for
bit 3
6
UI
tTTP2
Transmitter Pulse Position for
bit 2
7
UI
ΔtTTP
Offset Transmitter Pulse
Position (bit 6— bit 0)
65 MHzFigure 8
< +0.1
UI
tDD
Delay-Latency
Figure 3
10*T
T
tTPDD
Power Down Delay
active to OFF
65 MHz
Figure 4
7
12
ns
tTXZR
Enable Delay
OFF to active
65 MHz
Figure 5
40
55
ns
5
15
ns
5
15
ns
570
580
ns
50
65
ns
TxCLKOUT±
65 MHz
5 - 65 MHz
Figure 8
TxOUT[3:0]±
LVCMOS Outputs
tCLH
Low to High Transition Time
tCHL
High to Low Transition Time
tPASS
BIST PASS Valid Time,
BISTEN = 1, Figure 10
CL = 8 pF
Figure 2
LOCK, PASS
5 MHz
PASS
65 MHz
SSCG Mode
fDEV
fMOD
Spread Spectrum
Clocking Deviation
Frequency
Spread Spectrum
Clocking Modulation
Frequency
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(Note 10)
(Note 10)
8
TxCLKOUT = 5 to 65
MHz,
SSC[2:0] = ON
±0.5
±2
%
TxCLKOUT = 5 to 65
MHz,
SSC[2:0] = ON
8
100
kHz
Over 3.3V operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
fSCL
SCL Clock Frequency
tLOW
SCL Low Period
Conditions
Standard Mode
Fast Mode
Min
Max
Units
0
Typ
100
kHz
0
400
kHz
Standard Mode
4.7
us
Fast Mode
1.3
us
Standard Mode
4.0
us
tHIGH
SCL High Period
Fast Mode
0.6
us
tHD;STA
Hold time for a start or a
repeated start condition,
Figure 11
Standard Mode
4.0
us
0.6
us
Set Up time for a start or a
repeated start condition,
Figure 11
Standard Mode
4.7
us
0.6
us
Data Hold Time,
Figure 11
Standard Mode
0
3.45
us
Fast Mode
0
0.9
us
Data Set Up Time,
Figure 11
Standard Mode
250
ns
Fast Mode
100
ns
tSU;STO
Set Up Time for STOP
Condition, Figure 11
Standard Mode
4.0
us
Fast Mode
0.6
us
tBUF
Bus Free Time
Between STOP and START,
Figure 11
Standard Mode
4.7
us
1.3
us
SCL & SDA Rise Time,
Figure 11
Standard Mode
1000
ns
Fast Mode
300
ns
SCL & SDA Fall Time,
Figure 11
Standard Mode
300
ns
Fast mode
300
ns
Max
Units
0.7*
VDDIO
VDDIO
V
GND
0.3*
VDDIO
V
tSU:STA
tHD;DAT
tSU;DAT
tr
tf
Fast Mode
Fast Mode
Fast Mode
DC and AC Serial Control Bus Characteristics
Over 3.3V supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
VIH
Input High Level
SDA and SCL
VIL
Input Low Level Voltage
SDA and SCL
VHY
Input Hysteresis
SDA, IOL = 0.5mA
Iin
SDA or SCL, Vin = VDDIO or GND
SDA RiseTime – READ
tF
SDA Fall Time – READ
tSU;DAT
Set Up Time — READ
tHD;DAT
Hold Up Time — READ
tSP
Input Filter
Cin
Input Capacitance
Typ
>50
VOL
tR
Min
SDA, RPU = X, Cb ≤ 400pF
Figure 11
Figure 11
SDA or SCL
9
mV
0
0.36
V
-10
+10
µA
800
ns
50
ns
540
ns
600
ns
50
ns
<5
pF
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DS90UR908Q
Recommended Timing for the Serial Control Bus
DS90UR908Q
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability
and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in
the Recommended Operating Conditions is not implied. The Recommended Operating Conditions indicate conditions at which the device is functional and the
device should not be operated beyond such conditions.
Note 2: The Electrical Characteristics tables list guaranteed specifications under the listed Recommended Operating Conditions except as otherwise modified
or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not guaranteed.
Note 3: Typical values represent most likely parametric norms at VDD = 3.3V, Ta = +25 degC, and at the Recommended Operation Conditions at the time of
product characterization and are not guaranteed.
Note 4: Current into device pins is defined as positive. Current out of a device pin is defined as negative. Voltages are referenced to ground except VOD, ΔVOD,
VTH and VTL which are differential voltages.
Note 5: When the Serializer output is at TRI-STATE the Deserializer will lose PLL lock. Resynchronization / Relock must occur before data transfer require tPLD
Note 6: tPLD and tDDLT is the time required by the serializer and deserializer to obtain lock when exiting power-down state with an active PCLK.
Note 7: tDCCJ is the maximum amount of jitter between adjacent clock cycles.
Note 8: Supply noise testing was done with minimum capacitors on the PCB. A sinusoidal signal is AC coupled to the VDDn (1.8V) supply with amplitude = 100
mVp-p measured at the device VDDn pins. Bit error rate testing of input to the Ser and output of the Des with 10 meter cable shows no error when the noise
frequency on the Ser is less than 750 kHz. The Des on the other hand shows no error when the noise frequency is less than 400 kHz.
Note 9: Specification is guaranteed by characterization and is not tested in production.
Note 10: Specification is guaranteed by design and is not tested in production.
AC Timing Diagrams and Test Circuits
30105132
FIGURE 1. Checkerboard Data Pattern
30105105
FIGURE 2. LVCMOS Transition Times
30105111
FIGURE 3. Delay – Latency
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DS90UR908Q
30105188
FIGURE 4. FPD-Link & LVCMOS Powerdown Delay
30105189
FIGURE 5. FPD-Link Outputs Enable Delay
30105114
FIGURE 6. PLL Lock Times
11
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DS90UR908Q
30105106
FIGURE 7. FPD-Link (LVDS) Single-ended and Differential Waveforms
30105117
FIGURE 8. FPD-Link Transmitter Pulse Positions
30105116
FIGURE 9. Receiver Input Jitter Tolerance
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DS90UR908Q
30105190
FIGURE 10. BIST PASS Waveform
30105136
FIGURE 11. Serial Control Bus Timing Diagram
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DS90UR908Q
system complexity and overall cost. It also synchronizes to
the serializer regardless of the data pattern, delivering true
automatic “plug and lock” performance. It can lock to the incoming serial stream without the need of special training
patterns or sync characters. The DS90UR908Q recovers the
clock and data by extracting the embedded clock information,
validating and then deserializing the incoming data stream.
The DS90UR907Q / DS90UR908Q chipset supports 24-bit
color depth, HS, VS and DE video control signals and up to
three over-sampled low-speed (general purpose) data bits.
Functional Description
The DS90UR908Q receives 27-bits of data (24-high speed
bits and 3 low speed bits) over a single serial FPD-Link II pair
operating at 140Mbps to 1.82Gbps. The serial stream contains an embedded clock, video control signals and the DCbalance information which enhances signal quality and
supports AC coupling. The receiver converts the serial stream
into a 5-channel (4 data and 1 clock) FPD-Link LVDS Interface. The device is intended to be used with the
DS90UR907Q or the DS90UR905Q FPD-Link II serializers,
but is backward compatible with previous generation of FPDLink II as well.
The device converts a single input serial data stream to a
FPD-Link output bus, and also provides a signal check for the
chipset Built In Self Test (BIST) mode. The device can be
configured via external pins or through the optional serial
control bus. It features enhance signal quality on the link by
supporting the FPD-Link II data coding that provides randomization, scrambling, and DC balancing of the data. It also
includes multiple features to reduce EMI associated with display data transmission. This includes the randomization and
scrambling of the data, FPD-Link LVDS Output interface, and
also the output spread spectrum clock generation (SSCG)
support. The power saving features include a power down
mode, and optional LVCMOS (1.8 V) interface compatibility.
The DS90UR908Q can lock to a data stream without the use
of a separate reference clock source, which greatly simplifies
DATA TRANSFER
The DS90UR908Q will receive a pixel of data in the following
format: C1 and C0 represent the embedded clock in the serial
stream. C1 is always HIGH and C0 is always LOW. b[23:0]
contain the scrambled data. DCB is the DC-Balanced control
bit. DCB is used to minimize the short and long-term DC bias
on the signal lines. This bit determines if the data is unmodified or inverted. DCA is used to validate data integrity in the
embedded data stream. Both DCA and DCB coding schemes
are generated by the Ser and decoded by the Des automatically. Figure 12 illustrates the serial stream per PCLK cycle.
Note: The figure only illustrates the bits but does not actually
represent the bit location as the bits are scrambled and balanced continuously.
30105137
FIGURE 12. FPD-Link II Serial Stream
The device supports clocks in the range of 5 MHz to 65 MHz.
With every clock cycle 24 bits of payload are received along
with the four overhead bits. Thus, the line rate is 1.82 Gbps
maximum (140 Mbps minimum) with an effective data rate of
1.56 Gbps maximum. The link is extremely efficient at 86%
(24/28).
TABLE 1. DS90UR908Q Configuration Modes
CON
FIG1
OPERATING MODES AND BACKWARD COMPATIBILITY
(CONFIG[1:0])
The DS90UR908Q is backward compatible with previous
generations of FPD-Link II serializers. Configuration modes
are provided for backwards compatibility with the DS90C241
FPD-Link II Generation 1, and also the DS90UR241 or
DS99R421 FPD-Link II Generation 2 serializer by setting the
respective mode with the CONFIG[1:0] pins as shown in . The
selection also determine whether the Video Control Signal filter feature is enabled or disabled in Normal mode. This feature may be controlled by pin or by Register.
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CON Mode
FIG0
Des Device
L
L
Normal Mode, Control
Signal Filter disabled
DS90UR907Q,
DS90UR905Q
L
H
Normal Mode, Control
Signal Filter enabled
DS90UR907Q,
DS90UR905Q
H
L
Backwards Compatible
GEN2
DS90UR241
DS99R421
H
H
Backwards Compatible
GEN1
DS90C241
VIDEO CONTROL SIGNAL FILTER
When operating the devices in Normal Mode, the Video Control Signals (DE, HS, VS) have the following restrictions:
• Normal Mode with Control Signal Filter Enabled:
DE and HS — Only 2 transitions per 130 clock cycles are
transmitted, the transition pulse must be 3 PCLK or longer.
• Normal Mode with Control Signal Filter Disabled:
DE and HS — Only 2 transitions per 130 clock cycles are
transmitted, no restriction on minimum transition pulse.
• VS — Only 1 transition per 130 clock cycles are
transmitted, minimum pulse width is 130 clock cycles.
14
a visual display error. This feature allows for the chipset to
validate and filter out any high frequency noise on the control
signals. See Figure 13.
30105142
FIGURE 13. Video Control Signal Filter Wavefrom
OUT[3] shown in Figure 14 or MSBs on TxOUT[3] shown in
Figure 15. The user selects which mapping scheme is controlled by MAPSEL pin or by Register.
COLOR BIT MAPPING SELECT
The DS90UR908Q can be configured to accept 24-bit color
(8-bit RGB) with 2 different mapping schemes: LSBs on Tx-
30105165
FIGURE 14. 8–bit FPD-LInk Mapping: LSB's on TxOUT3
15
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DS90UR908Q
Video Control Signals are defined as low frequency signals
with limited transitions. Glitches of a control signal can cause
DS90UR908Q
30105166
FIGURE 15. 8–bit FPD-LInk Mapping: MSB's on TxOUT3
the Data and PCLK output states are determined by the
OSS_SEL status. Note – in POWER DOWN, the optional Serial Bus Control Registers are RESET.
FPD-LINK II INPUT
Common Mode Filter Pin (CMF) — Optional
The DS90UR908Q provides access to the center tap of the
internal termination. A capacitor may be placed on this pin for
additional common-mode filtering of the differential pair. This
can be useful in high noise environments for additional noise
rejection capability. A 4.7 µF capacitor may be connected to
this pin to Ground.
Stop Stream SLEEP Feature
The DS90UR908Q will enter a low power SLEEP state when
the input serial stream is stopped. A STOP condition is detected when the embedded clock bits are not present. When
the serial stream starts again, the Des will then lock to the
incoming signal and recover the data. Note – in STOP
STREAM SLEEP, the optional Serial Bus Control Registers
values are RETAINED.
Input Equalizer Gain (EQ)
The DS90UR908Q can enable receiver input equalization of
the serial stream to compensate the cable loss and increase
the eye opening to the input. The equalization feature may be
controlled by the EQ pin (strap option) Table 4 or by register
Table 8.
OUTPUT INTERFACES (LVCMOS & FPD-LINK)
CLOCK-DATA RECOVERY STATUS FLAG (LOCK),
OUTPUT ENABLE (OEN) and OUTPUT STATE SELECT
(OSS_SEL)
When PDB is driven HIGH, the CDR PLL begins locking to
the serial input, LOCK is Low and the FPD-Link interface state
is determined by the state of the OSS_SEL pin.
After the DS90UR908Q completes its lock sequence to the
input serial data, the LOCK output is driven HIGH, indicating
valid data and clock recovered from the serial input is available on the FPD-Link outputs. The TxCLK output is held at its
current state at the change from OSC_CLK (if this is enabled
via OSC_SEL) to the recovered clock (or vice versa). Note
that the FPD-Link outputs may be held in an inactive state
(TRI-STATE) through the use of the Output Enable pin (OEN).
If there is a loss of clock from the input serial stream, LOCK
is driven Low and the state of the outputs are based on the
OSS_SEL setting (configuration pin or register).
TABLE 2. EQ Pin Configuration Table
EQ (Strap Option)
Effect
L
EQ = Off
H
~12 dB
POWER SAVING FEATURES
PowerDown Feature (PDB)
The DS90UR908Q has a PDB input pin to ENABLE or POWER DOWN the device. This pin can be controlled by the
system to save power, disabling the Des when the display is
not needed. An auto detect mode is also available. In this
mode, the PDB pin is tied High and the Des will enter POWER
DOWN when the serial stream stops. When the serial stream
starts up again, the Des will lock to the input stream and assert
the LOCK pin and output valid data. In POWER DOWN mode,
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16
DS90UR908Q
TABLE 3. Output State Table
INPUTS
OUTPUTS
PDB
OEN
OSS_SEL
LOCK
OTHER OUTPUTS
L
X
X
X
TxCLKOUT is TRI-STATE
TxOUT[3:0] areTRI-STATE
PASS is TRI-STATE
L
X
L
L
TxCLKOUT is TRI-STATE
TxOUT[3:0] areTRI-STATE
PASS is HIGH
H
L
H
L
TxCLKOUT is TRI-STATE
TxOUT[3:0] areTRI-STATE
PASS is TRI-STATE
H
H
H
L
TxCLKOUT is TRI-STATE or OSC Output through Register
bit
TxOUT[3:0] areTRI-STATE
PASS is TRI-STATE
H
L
X
H
TxCLKOUT is TRI-STATE
TxOUT[3:0] areTRI-STATE
PASS is HIGH
H
H
X
H
TxCLKOUT is Active
TxOUT[3:0] are Active
PASS is Active
(Normal operating mode)
LVCMOS 1.8V / 3.3V VDDIO Operation
The LVCMOS outputs can operate with 1.8 V or 3.3 V levels
(VDDIO) for target (Display) compatibility. The 1.8 V levels will
offer a system power savings. This applies to the following
pins: PASS and LOCK.
SSCG GENERATION — OPTIONAl
The Des provides an internally generated spread spectrum
clock (SSCG) to modulate its outputs. Both clock and data
outputs are modulated. This will aid to lower system EMI.
Output SSCG deviations to ±2.0% (4% total) at up to 35kHz
modulations nominally are available. See Table 5 and Table
6. This feature may be controlled by pins or by register. The
LFMODE should be set appropriately if the SSCG is being
used. Set LFMODE High if the clock frequency is between 5
MHz and 20 MHz, set LFMODE Low if the clock frequency is
between 20 MHz and 65 MHz.
FPD-LINK OUTPUT
VODSEL
The differential output voltage of the FPD-Link interface is
controlled by the VODSEL input.
TABLE 4. VODSEL Configuration Table
VODSEL
Result
L
VOD is 250mV TYP (500mVp-p)
H
VOD is 400mV TYP (800mVp-p)
TABLE 5. SSCG Configuration (LFMODE = L) — Des Output
SSC[2:0] Inputs
LFMODE = L (20 - 65 MHz)
Result
SSC2
SSC1
SSC0
fdev (%)
fmod (kHz)
L
L
L
OFF
OFF
L
L
H
±0.9
L
H
L
±1.2
L
H
H
±1.9
H
L
L
±2.3
H
L
H
±0.7
H
H
L
±1.3
H
H
H
±1.7
17
CLK/2168
CLK/1300
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DS90UR908Q
TABLE 6. SSCG Configuration (LFMODE = H) — Des Output
SSC[2:0] Inputs
LFMODE = H (5 - 20 MHz)
SSC2
SSC1
L
L
Result
SSC0
fdev (%)
fmod (kHz)
L
L
OFF
OFF
L
H
±0.7
L
H
L
±1.3
L
H
H
±1.8
H
L
L
±2.2
H
L
H
±0.7
H
H
L
±1.2
H
H
H
±1.7
CLK/625
CLK/385
OSCILLATOR OUTPUT — OPTIONAL
The DS90UR908Q provides an optional TxCLKOUT when
the input clock (serial stream) has been lost. This is based on
an internal oscillator. The frequency of the oscillator may be
selected. This feature may be controlled by the external pin
and the register. See Tables 3, 8.Figure 17
30105133
FIGURE 16. SSCG Waveform
30105154
FIGURE 17. TxCLKOUT Output Oscillator Option Enabled
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18
An optional At-Speed Built In Self Test (BIST) feature supports the testing of the high-speed serial link. This is useful in
the prototype stage, equipment production, in-system test
and also for system diagnostics. In the BIST mode only an
input clock is required along with control to the Ser and Des
BISTEN input pins. The Ser outputs a test pattern (PRBS7)
and drives the link at speed. The Des detects the PRBS7 pattern and monitors it for errors. The PASS output pin toggles
to flag any payloads that are received with 1 to 24 bit errors.
The BISTM pin selects the operational mode of the PASS pin.
If BISTM = L, the PASS pins reports the final result only. If
BISTM = H, the PASS pins counts payload errors and also
results the result. The result of the test is held on the PASS
output until reset (new BIST test or Power Down). A high on
PASS indicates NO ERRORS were detected. A Low on PASS
indicates one or more errors were detected. The duration of
the test is controlled by the pulse width applied to the Des
BISTEN pin.
Sample BIST Sequence
SeeFigure 18 for the BIST mode flow diagram.
Step 1: Place the DS90UR907Q or DS90UR905Q in BIST
Mode by setting BISTEN = H. The BIST Mode is enabled via
the BISTEN pin. An RxCLKIN or PCLK is required for all the
Ser options. When the DS90UR908Q detects the BIST mode
pattern and command (DCA and DCB code) the RGB and
control signal outputs are shut off.
30105143
FIGURE 18. BIST Mode Flow Diagram
19
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DS90UR908Q
Step 2: Place the DS90UR908Q in BIST mode by setting the
BISTEN = H. The Device is now in the BIST mode and checks
the incoming serial payloads for errors. If an error in the payload (1 to 24) is detected, the PASS pin will switch low for one
half of the clock period. During the BIST test, the PASS output
can be monitored and counted to determine the payload error
rate.
Step 3: To Stop the BIST mode, the DS90UR908Q BISTEN
pin is set Low. It stops checking the data and the final test
result is held on the PASS pin. If the test ran error free, the
PASS output will be High. If there was one or more errors
detected, the PASS output will be Low. The PASS output
state is held until a new BIST is run, the device is RESET, or
Powered Down. The BIST duration is user controlled by the
duration of the BISTEN signal.
Step 4: To return the link to normal operation, the serializer
BISTEN input is set Low. The Link returns to normal operation.
Figure 19 shows the waveform diagram of a typical BIST test
for two cases. Case 1 is error free, and Case 2 shows one
with multiple errors. In most cases it is difficult to generate
errors due to the robustness of the link (differential data transmission etc.), thus they may be introduced by greatly extending the cable length, faulting the interconnect, reducing signal
condition enhancements (De-Emphasis, VODSEL, or Rx
Equalization).
Built In Self Test (BIST) — Optional
DS90UR908Q
30105164
FIGURE 19. BIST Waveforms
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20
DS90UR908Q
Serial Bus Control — Optional
The DS90UR908Q may also be configured by the use of a
serial control bus that is I2C protocol compatible. By default,
the I2C reg_0x00'h is set to 00'h and all configuration is set
by control/strap pins. A write of 01'h to reg_0x00'h will enable/
allow configuration by registers; this will override the control/
strap pins. Multiple devices may share the serial control bus
since multiple addresses are supported. See Figure 20.
The serial bus is comprised of three pins. The SCL is a Serial
Bus Clock Input. The SDA is the Serial Bus Data Input / Output signal. Both SCL and SDA signals require an external pull
up resistor to VDDIO. For most applications a 4.7 k pull up resistor to VDDIO may be used. The resistor value may be
adjusted for capacitive loading and data rate requirements.
The signals are either pulled High, or driven Low.
30105141
FIGURE 20. Serial Control Bus Connection
30105151
FIGURE 21. START and STOP Conditions
The third pin is the ID[X] pin. This pin sets one of five possible
device addresses. Two different connections are possible.
The pin may be pulled to VDD (1.8V, NOT VDDIO)) with a 10
kΩ resistor. Or a 10 kΩ pull up resistor (to VDD 1.8V, NOT
VDDIO)) and a pull down resistor of the recommended value
to set other three possible addresses may be used. See Table
7 for the Des. Do not tie ID[x] directly to ground.
The Serial Bus protocol is controlled by START, START-Repeated, and STOP phases. A START occurs when SCL
transitions Low while SDA is High. A STOP occurs when SDA
transition High while SCL is also HIGH. See Figure 21
To communicate with a remote device, the host controller
(master) sends the slave address and listens for a response
from the slave. This response is referred to as an acknowledge bit (ACK). If a slave on the bus is addressed correctly,
it Acknowledges (ACKs) the master by driving the SDA bus
low. If the address doesn't match a device's slave address, it
Not-acknowledges (NACKs) the master by letting SDA be
pulled High. ACKs also occur on the bus when data is being
transmitted. When the master is writing data, the slave ACKs
after every data byte is successfully received. When the master is reading data, the master ACKs after every data byte is
received to let the slave know it wants to receive another data
byte. When the master wants to stop reading, it NACKs after
the last data byte and creates a stop condition on the bus. All
communication on the bus begins with either a Start condition
or a Repeated Start condition. All communication on the bus
ends with a Stop condition. A READ is shown in Figure 22
and a WRITE is shown in Figure 23.
If the Serial Bus is not required, the three pins may be left
open (NC).
TABLE 7. ID[x] Resistor Value
21
Resistor
RID kΩ
(5%tol)
Address
7'b
Address
8'b
0 appended
(WRITE)
0.47
7b' 111 0001 (h'71)
8b' 1110 0010 (h'E2)
2.7
7b' 111 0010 (h'72)
8b' 1110 0100 (h'E4)
8.2
7b' 111 0011 (h'73)
8b' 1110 0110 (h'E6)
Open
7b' 111 0110 (h'76)
8b' 1110 1100 (h'EC)
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DS90UR908Q
30105138
FIGURE 22. Serial Control Bus — READ
30105139
FIGURE 23. Serial Control Bus — WRITE
TABLE 8. Serial Bus Control Registers
ADD ADD Register Name
(dec) (hex)
0
1
0
1
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Des Config 1
Slave ID
Bit(s)
R/W
Defa Function
ult
(bin)
Description
7
R/W
0
LFMODE
0: 20 to 65 MHz Operation
1: 5 to 20 MHz Operation
6
R/W
0
MAPSEL
FPD-Link Map Select
0: LSB on TxOUT3+/1: MSB on TxOUT3+/-
5
R/W
0
Reserved
Reserved
4
R/W
0
Reserved
Reserved
3:2
R/W
00
CONFIG
00: Normal Mode, Control Signal Filter Disabled
01: Normal Mode, Control Signal Filter Enabled
10: Backwards Compatible (DS90UR241)
11: Backwards Compatible (DS90C241)
1
R/W
0
SLEEP
Note – not the same function as PowerDown (PDB)
0: normal mode
1: Sleep Mode – Register settings retained.
0
R/W
0
REG Control
0: Configurations set from control pins / STRAP pin
1: Configurations set from registers (except I2C_ID)
7
R/W
0
6:0
R/W
0: Address from ID[X] Pin
1: Address from Register
1110 ID[X]
000
Serial Bus Device ID, Four IDs are:
7b '1110 001 (h'71); 8b ' 1110 0010 (h'E2)
7b '1110 010 (h'72); 8b ' 1110 0100 (h'E4)
7b '1110 011 (h'73); 8b ' 1110 0110 (h'E6)
7b '1110 110 (h'76); 8b ' 1110 1100 (h'EC)
All other addresses are Reserved.
22
2
3
2
3
Des Features 1
Des Features 2
Defa Function
ult
(bin)
DS90UR908Q
ADD ADD Register Name
(dec) (hex)
Bit(s)
R/W
7
R/W
0
OEN
Output Enable Input
Table 3
6
R/W
0
OSS_SEL
Output Sleep State Select
Table 3
5:4
R/W
00
Reserved
Reserved
3
R/W
0
VODSEL
Differential Driver Output Voltage Select
0: LVDS VOD is ±250 mV, 500 mVp-p (typ)
1: LVDS VOD is ±400 mV, 800 mVp-p (typ)
2:0
R/W
00
OSC_SEL
000: OFF
001: Reserved
010: 25 MHz ±40%
011: 16.7 MHz ±40%
100: 12.5 MHz ±40%
101: 10 MHz ±40%
110: 8.3 MHz ±40%
111: 6.3 MHz ±40%
7:5
R/W
000
EQ Gain
000: ~1.625 dB
001: ~3.25 dB
010: ~4.87 dB
011: ~6.5 dB
100: ~8.125 dB
101: ~9.75 dB
110: ~11.375 dB
111: ~13 dB
4
R/W
0
EQ Enable
0: EQ = disabled
1: EQ = enabled
3
R/W
0
Reserved
Reserved
2:0
R/W
000
SSC
IF LFMODE = 0, then:
000: SSCG OFF
001: fdev = ±0.9%, fmod = CLK/2168
010: fdev = ±1.2%, fmod = CLK/2168
011: fdev = ±1.9%, fmod = CLK/2168
100: fdev = ±2.3%, fmod = CLK/2168
101: fdev = ±0.7%, fmod = CLK/1300
110: fdev = ±1.3%, fmod = CLK/1300
111: fdev = ±1.57%, fmod = CLK/1300
IF LFMODE = 1, then:
000: SSCG OFF
001: fdev = ±0.7%, fmod = CLK/625
010: fdev = ±1.3%, fmod = CLK/625
011: fdev = ±1.8%, fmod = CLK/625
100: fdev = ±2.2%, fmod = CLK/625
101: fdev = ±0.7%, fmod = CLK/385
110: fdev = ±1.2%, fmod = CLK/385
111: fdev = ±1.7%, fmod = CLK/385
23
Description
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DS90UR908Q
Applications Information
tions. In this application three to six general purpose signals
may also be send from host to display.
DISPLAY APPLICATION
The DS90UR908Q, in conjunction with the DS90UR907Q or
DS90UR905Q, is intended for interfacing between a host
(graphics processor) and a Display. It supports an 24-bit color
depth (RGB888) and up to 1024 X 768 display formats. In a
RGB888 application, 24 color bits (R[7:0], G[7:0], B[7:0]), Pixel Clock (PCLK) and three control bits (VS, HS and DE) are
supported across the serial link with PCLK rates from 5 to 65
MHz. The device may also be used in 18-bit color applica-
TYPICAL APPLICATION CONNECTION
Figure 24 shows a typical application of the DS90UR908Q for
a 65 MHz XGA Display. The LVDS inputs utilize 100 nF coupling capacitors to the line and the Receiver provides internal
termination. Bypass capacitors are placed near the power
supply pins. Ferrite beads are placed on the power lines for
effective noise suppression.
30105145
FIGURE 24. DS90UR908Q Typical Connection Diagram
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24
LIVE LINK INSERTION
The serializer and deserializer devices support live pluggable
applications. The automatic receiver lock to random data
“plug & go” hot insertion capability allows the DS90UR908Q
to attain lock to the active data stream during a live insertion
event.
ALTERNATE COLOR / DATA MAPPING
Color Mapped data Pin names are provided to specify a recommended mapping for 24-bit and 18-bit Applications. When
connecting to earlier generations of FPD-Link II serializer devices, a color mapping review is recommended to ensure the
correct connectivity is obtained. Table 9 provides examples
for interfacing between DS90UR908Q and different deserializers.
TRANSMISSION MEDIA
The FPD-Link II chipset is intended to be used in a point-topoint configuration, through a PCB trace, or through twisted
pair cable. The serializer and deserializer provide internal terminations providing a clean signaling environment. The interconnect for LVDS should present a differential impedance of
TABLE 9. Alternate Color / Data Mapping
FPD-Link
Bit Number
RGB (LSB
Example)
DS90UR905Q
TxOUT3
Bit 26
B1
B1
Bit 25
B0
B0
Bit 24
G1
G1
Bit 23
G0
G0
Bit 22
R1
R1
Bit 21
R0
R0
Bit 20
DE
DE
DIN20
Bit 19
VS
VS
DIN19
DIN19
Bit 18
HS
HS
DIN18
DIN18
Bit 17
B7
B7
DIN17
DIN17
Bit 16
B6
B6
DIN16
DIN16
Bit 15
B5
B5
DIN15
DIN15
Bit 14
B4
B4
DIN14
Bit 13
B3
B3
DIN13
Bit 12
B2
B2
DIN12
DIN12
Bit 11
G7
G7
DIN11
DIN11
Bit 10
G6
G6
DIN10
DIN10
Bit 9
G5
G5
DIN9
DIN9
Bit 8
G4
G4
DIN8
DIN8
Bit 7
G3
G3
DIN7
Bit 6
G2
G2
DIN6
Bit 5
R7
R7
DIN5
DIN5
Bit 4
R6
R6
DIN4
DIN4
Bit 3
R5
R5
DIN3
DIN3
Bit 2
R4
R4
DIN2
DIN2
Bit 1
R3
R3
DIN1
DIN1
Bit 0
R2
R2
DIN0
N/ADIN12
DIN23
OS2
DIN23
DIN22
OS1
DIN22
DIN21
OS0
TxOUT2
TxOUT1
TxOUT0
N/A
DS90UR908Q
Settings
MAPSEL = 0
CONFIG [1:0] = 00
25
DS90UR241 DS99R421
DS90C241
N/A
RxIN2
DIN20
DIN14
RxIN1
DIN13
DIN7
RxIN0
DIN6
DIN0
CONFIG [1:0] = 10
DIN21
CONFIG [1:0] = 11
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DS90UR908Q
100 Ohms. Use cables and connectors that have matched
differential impedance to minimize impedance discontinuities.
Shielded or un-shielded cables may be used depending upon
the noise environment and application requirements.
POWER UP REQUIREMENTS AND PDB PIN
The VDD (VDDn), VDDTX and VDDIO supply ramps should be
faster than 1.5 ms with a monotonic rise. Supplies may power
up in any order, however device operation should be initiated
only after all supplies are in their valid operating ranges. The
optional serial bus address selection is done upon power up
also. Thus, if using this optional feature, the PDB signal must
be delayed to allow time for the ID setting to occur. The delay
maybe done by simply holding the PDB pin at a Low, or with
an external RC delay based off the VDDIO rail which would then
need to lag the others in time. If the PDB pin is pulled to
VDDIO, it is recommended to use a 10 kΩ pull-up and a 10 uF
cap to GND to delay the PDB input signal.
DS90UR908Q
Some devices provide separate power and ground pins for
different portions of the circuit. This is done to isolate switching noise effects between different sections of the circuit.
Separate planes on the PCB are typically not required. Pin
Description tables typically provide guidance on which circuit
blocks are connected to which power pin pairs. In some cases, an external filter many be used to provide clean power to
sensitive circuits such as PLLs.
Use at least a four layer board with a power and ground plane.
Locate LVCMOS signals away from the LVDS lines to prevent
coupling from the LVCMOS lines to the LVDS lines. Closelycoupled differential lines of 100 Ohms are typically recommended for LVDS interconnect. The closely coupled lines
help to ensure that coupled noise will appear as commonmode and thus is rejected by the receivers. The tightly coupled lines will also radiate less.
Information on the LLP style package is provided in National
Application Note: AN-1187.
PCB LAYOUT AND POWER SYSTEM CONSIDERATIONS
Circuit board layout and stack-up for the LVDS devices should
be designed to provide low-noise power feed to the device.
Good layout practice will also separate high frequency or
high-level inputs and outputs to minimize unwanted stray
noise pickup, feedback and interference. Power system performance may be greatly improved by using thin dielectrics (2
to 4 mils) for power / ground sandwiches. This arrangement
provides plane capacitance for the PCB power system with
low-inductance parasitics, which has proven especially effective at high frequencies, and makes the value and placement
of external bypass capacitors less critical. External bypass
capacitors should include both RF ceramic and tantalum electrolytic types. RF capacitors may use values in the range of
0.01 uF to 0.1 uF. Tantalum capacitors may be in the 2.2 uF
to 10 uF range. Voltage rating of the tantalum capacitors
should be at least 5X the power supply voltage being used.
Surface mount capacitors are recommended due to their
smaller parasitics. When using multiple capacitors per supply
pin, locate the smaller value closer to the pin. A large bulk
capacitor is recommend at the point of power entry. This is
typically in the 50uF to 100uF range and will smooth low frequency switching noise. It is recommended to connect power
and ground pins directly to the power and ground planes with
bypass capacitors connected to the plane with via on both
ends of the capacitor. Connecting power or ground pins to an
external bypass capacitor will increase the inductance of the
path.
A small body size X7R chip capacitor, such as 0603, is recommended for external bypass. Its small body size reduces
the parasitic inductance of the capacitor. The user must pay
attention to the resonance frequency of these external bypass
capacitors, usually in the range of 20-30 MHz. To provide effective bypassing, multiple capacitors are often used to
achieve low impedance between the supply rails over the frequency of interest. At high frequency, it is also a common
practice to use two vias from power and ground pins to the
planes, reducing the impedance at high frequency.
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LVDS INTERCONNECT GUIDELINES
See AN-1108 and AN-905 for full details.
• Use 100Ω coupled differential pairs
• Use the S/2S/3S rule in spacings
– S = space between the pair
– 2S = space between pairs
– 3S = space to LVCMOS signal
• Minimize the number of Vias
• Use differential connectors when operating above
500Mbps line speed
• Maintain balance of the traces
• Minimize skew within the pair
• Terminate as close to the TX outputs and RX inputs as
possible
Additional general guidance can be found in the LVDS
Owner’s Manual - available in PDF format from the National
web site at: www.national.com/lvds
26
•
•
08/09/2010 — Update Pin Description of VODSEL
03/30/2010 — Initial Release
07/26/2010 — Update all final AC and DC parameter
limits
27
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DS90UR908Q
•
Revision History
DS90UR908Q
Physical Dimensions inches (millimeters) unless otherwise noted
48–pin LLP Package (7.0 mm x 7.0 mm x 0.8 mm, 0.5 mm pitch)
NS Package Number SQA48A
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28
DS90UR908Q
Notes
29
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DS90UR908Q 5 - 65 MHz 24-bit Color FPD-Link II to FPD-Link Converter
Notes
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