DS99R421 5-43 MHz FPD-Link LVDS (3 Data + 1 Clock) to Single Embedded Clock DC-Balanced LVDS Converter General Description Features The DS99R421 converts a FPD-Link input with 4 non-DC Balanced LVDS (3 LVDS Data + LVDS Clock) plus 3 oversampled low speed control bits into a single LVDS DC-balanced serial stream with embedded clock information. This single serial stream simplifies transferring the 24-bit bus over a single differential pair of PCB traces and cable by eliminating the skew problems between the 3 parallel LVDS data inputs and LVDS clock paths. It saves system cost by narrowing 4 LVDS pairs to 1 LVDS pair that in turn reduce PCB layers, cable width, connector size, and pins. The DS99R421 incorporates a single serialized LVDS signal on the high-speed I/O. Embedded clock LVDS provides a low power and low noise environment for reliably transferring data over a serial transmission path. By optimizing the converter output edge rate for the operating frequency range EMI is further reduced. In addition the device features pre-emphasis to boost signals over longer distances using lossy cables. Internal DC balanced encoding is used to support AC-Coupled interconnects. ■ 5 MHz–43 MHz embedded clock & DC-Balanced data transmission (21 total LVDS data bits plus 3 low speed LVCMOS data bits) ■ User adjustable pre-emphasis driving ability through external resistor on LVDS outputs and capable to drive up to 10 meters shielded twisted-pair cable ■ Supports AC-coupling data transmission ■ 100Ω Integrated termination resistor at LVDS input ■ Power-down control ■ Available @SPEED BIST to DS90UR124 to validate link integrity ■ All LVCMOS inputs & control pins have internal pulldown ■ Schmitt trigger inputs on OS[2:0] to minimize metastable ■ ■ ■ ■ ■ ■ conditions. Outputs Tri-Stated through DEN On-chip filters for PLLs Power supply range 3.3V ± 10% Automotive temperature range −40°C to +105°C Greater than 8kV ESD Tolerance Meets ISO 10605 ESD and AEC-Q100 compliance Block Diagram 30011301 FIGURE 1. Block Diagram TRI-STATE® is a registered trademark of National Semiconductor Corporation. © 2007 National Semiconductor Corporation 300113 www.national.com DS99R421 5-43 MHz FPD-Link LVDS (3 Data + 1 Clock) to Single Embedded Clock DC-Balanced LVDS Converter December 3, 2007 DS99R421 Application Overview 30011302 FIGURE 2. Typical Application Diagram www.national.com 2 RD = 2 kΩ, CS = 150/330 pF Contact Discharge DOUT± Air Discharge DOUT± Supply Voltage (VDD) −0.3V to +4V LVCMOS Input Voltage −0.3V to (VDD +0.3V) LVCMOS Output Voltage −0.3V to (VDD +0.3V) LVDS Receiver Input Voltage −0.3V to +3.9V LVDS Driver Output Voltage −0.3V to +3.9V LVDS Output Short Circuit Duration 10 ms Junction Temperature +150°C Storage Temperature −65°C to +150°C Lead Temperature (Soldering, 4 seconds) +260°C Maximum Package Power Dissipation Capacity Package De-rating: 1/θJA °C/W above +25°C DS99R421 − 36L LLP 37.6 (4L*); 83.7 (2L*)°C/W θJC 3.1 (2/4L*) °C/W *JEDEC ±10 kV ±25 kV Recommended Operating Conditions Supply Voltage (VDD) Operating Free Air Temperature (TA) Input Clock Rate RxCLKIN± Supply Noise (VDDp-p) Min 3.0 Nom 3.3 Max 3.6 Units V −40 +25 +105 °C 5 Receiver Input Range 43 MHz ±100 mVP-P VDD V 0 Electrical Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions Pin/Freq. Min PWDNB, DEN, VODSEL, BISTEN Typ Max Units 2.0 VDD V GND 0.8 V LVCMOS & SCHMITT-TRIGGER INPUT DC SPECIFICATIONS VIH High Level Input Voltage VIL Low Level Input Voltage VCL Input Clamp Voltage ICL = −18 mA IIN Input Current VIN = 0V or 3.6V VTH+ High Level Input Voltage VTH− High Level Input Voltage VH Hysteresis Voltage −0.9 −10 OS[2:0] (Schmitt-triggered Inputs) VTH+ – VTH− −1.5 V +10 µA 2.0 200 V 400 0.8 V 600 mV +100 mV LVDS DC SPECIFICATIONS VTH Differential Threshold High VCM = 1.2V Voltage VTL Differential Threshold Low Voltage |VID| Differential Input Voltage Swing VCM Common Mode Voltage IIN Input Current LVDS differential Inputs: RxIN0±, RxIN1±, RxIN2±, RxCLKIN± −100 mV 100 0.525 1.2 600 mV VDD− (VID/2) mV VIN = +2.4V, VDD = 3.6V −10 +10 µA VIN = 0V, VDD = 3.6V -10 +10 µA 3 www.national.com DS99R421 ESD Rating (ISO10605) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. θJA ≥±8 kV DS99R421 meets ISO10605 ESD Rating (HBM) Absolute Maximum Ratings (Note 1) DS99R421 Symbol VOD Parameter Conditions Output Differential Voltage RT = 100Ω (Figure 10) VODSEL = L Pin/Freq. Min Typ Max Units LVDS differential Outputs: DOUT± 380 500 630 mV 650 900 1150 mV 10 50 mV 1.2 1.5 V 5 50 mV RT = 100Ω VODSEL = H ΔVOD Output Differential Voltage RT = 100Ω Unbalance VOS Output Voltage Offset RT = 100Ω PRE = H (off) ΔVOS Output Voltage Offset Difference RT = 100Ω PRE = H (off) IOS Output Short Circuit Current DOUT± = 0V VODSEL = L PRE = H (off) −2 −8 mA DOUT± = 0V VODSEL = H PRE = H (off) −7 −13 mA IOZ 1.0 TRI-STATE Output Current PWDNB = 0V, DOUT± = 0V OR VDD (inputs not toggling) RT Internal Input Termination Resistance RxIN: across RxIN(2:0)+ & RxIN (2:0)−, and across RxCLKIN+ & RxCLKIN− −10 ±1 +10 µA 90 105 130 Ω CONVERTER SUPPLY CURRENT IDD IDDTZ Total Supply Current (includes load current) f = 43 MHz RT = 100Ω CHECKERBOARD pattern PRE = 6 KΩ (Figure 3) 95 130 mA Supply Current Powerdown PWDNB = 0V (inputs not toggling) 2 50 µA Receiver Input Timing Requirements Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions tRCIH Receiver Clock Input High Time Referenced to rising edge of RxCLKIN tRCIL Receiver Clock Input Low Time Referenced to rising edge of RxCLKIN Min Typ 0.35T 0.57T 0.43T Max Units ns 0.65T ns Receiver Input Switching Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions Pin/Freq. RITOL-L Receiver Input Tolerance Left (Figures 7, 8) (Notes 8, 10) 5 MHz–43 MHz RITOL-R Receiver Input Tolerance Right (Figures 7, 8) (Notes 8, 10) 5 MHz–43 MHz Unit Interval (Note 8) 5 MHz–43 MHz UI www.national.com 4 Min Typ 1/7th of RxCLKIN Max Units 0.3 UI 0.3 UI ns Over recommended operating supply and temperature ranges unless otherwise specified. Symbol FOS[2:0] Parameter Conditions Maximum Frequency Limitation of OS[2:0] Pin/Freq. Min Typ OS[2:0] Max Units FRxCLKIN / 5 MHz Input to Output Switching Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions Pin/Freq. RCTCD RxCLK IN to DOUT Delay (Figure 5), (Note 9) 5 MHz–43 MHz PDD Power Down Delay 5 MHz–43 MHz Min Typ Max Units 4T + 1.0 4T + 5.0 4T + 10.0 ns 1 µs Serializer Output Switching Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions tLLHT LVDS Low-to-High Transition Time tLHLT LVDS High-to-Low Transition Time RT = 100Ω, CL = 10 pF to GND (Figure 4) tPLT PLL Lock Time 5 MHz–43 MHz TxOUT_E_O TxOUT_Eye_Opening (Notes 8, 11) (Figure 9) 5 MHz–43 MHz (respect to ideal) UI 5 MHz–43 MHz Unit Interval (Note 8) Min Typ Max Units 0.3 0.5 ns 0.3 0.5 ns 10 ms 0.78 UI 1/28th of DOUT ns 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 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: Specification is guaranteed by characterization and is not tested in production. Note 6: Specification is guaranteed by design and is not tested in production. Note 7: Total Interconnect Jitter Budget (tJIT) specifies the allowable jitter added by the interconnect assuming both transmitter and receiver are SerDes circuits. Note 8: UI – Unit Interval, equivalent to one ideal serialized data bit width. The UI scales with frequency. For the input, it is 1/7th the input clock period. Example 43 MHz = 23.26 ns. 1/7th of this is 3.32 ns. This is 1 UI of the input at 43 MHz. For the output, it is 1/28th of the input clock period. Example 43 MHz = 23.26 ns. 1/28th of this is 831 ps. This is 1 UI of the output at 43 MHz. Note 9: A Clock Unit Symbol (T) is defined as 1/ (Line rate of RxCLKIN). Note 10: Receiver Input Tolerance is defined as the valid data sampling region at the receiver inputs. This margin takes into account the transmitter pulse positions (min and max) and the receiver input setup and hold time (internal data sampling window – RSPos). This margin allows for LVDS interconnect skew, inter-symbol interference (both dependent on type/length of cable), and clock jitter. Note 11: TxOUT_E_O is affected by pre-emphasis value. 5 www.national.com DS99R421 Input Timing Requirements for OS[2:0] DS99R421 AC Timing Diagrams and Test Circuits 30011306 FIGURE 3. LVDS Input Checkerboard Pattern 30011307 FIGURE 4. Serializer LVDS Output Load and Transition Times 30011308 FIGURE 5. RxIN to DOUT Delay – RCTCD www.national.com 6 DS99R421 30011309 FIGURE 6. Receiver LVDS Input Mapping 30011310 FIGURE 7. Receiver RITOL Min and Max 7 www.national.com DS99R421 30011311 FIGURE 8. Receiver RITOL Left and Right 30011312 FIGURE 9. Serializer Output Eye Opening 30011313 FIGURE 10. Serializer VOD Diagram www.national.com 8 DS99R421 Pin Descriptions Pin # Pin Name I/O/PWR Description FPD-LINK LVDS RECEIVER INPUT PINS 28, 30, 32 RxIN[2:0]− LVDS_I LVDS Receiver inverted Data Inputs (−) 29, 31, 33 RxIN[2:0]+ LVDS_I LVDS Receiver true Data Inputs (+) 34 RxCLKIN− LVDS_I LVDS Receiver inverted reference Clock Inputs. Used to strobe data at the RxIN inputs and to drive the receiver PLL 35 RxCLKIN+ LVDS_I LVDS Receiver true reference Clock Inputs. Used to strobe data at the RxIN inputs and to drive the receiver PLL LVCMOS_I Over Sampled Receiver Data Inputs with Schmitt trigger OVER SAMPLED INPUT PINS 3-1 OS[2:0] CONTROL AND CONFIGURATION PINS 4 PWDNB LVCMOS_I Power Down Bar PWDNB = H; Device is Enabled and ON PWDNB = L; Device is in power down mode (Sleep), LVDS Driver DOUT (+/-) Outputs are in TRI-STATE stand-by mode, PLL is shutdown to minimize power consumption. 15 DEN LVCMOS_I Data Enable DEN = H; LVDS Driver Outputs are Enabled (ON). DEN = L; LVDS Driver Outputs are Disabled (OFF), Serializer LVDS Driver DOUT (+/-) Outputs are in TRI-STATE, PLL still operational and locked to TCLK. 10 PRE LVCMOS_I Pre-emphasis Level Select PRE = NC (No Connect); Pre-emphasis is Disabled (OFF). Pre-emphasis is active when input is tied to VSS through external resistor RPRE. Resistor value determines pre-emphasis level. Recommended value RPRE ≥ 6 kΩ; Imax = [48 / RPRE], RPREmin = 6 kΩ See Applications Information section for more details. 18 VODSEL LVCMOS_I VOD Level Select VODSEL = L; LVDS Driver Output is ±500 mV (RT = 100Ω) VODSEL = H; LVDS Driver Output is ±900 mV (RT = 100Ω) For normal applications, set this pin LOW. For long cable applications where a larger VOD is required, set this pin HIGH. See Applications Information section for more details. 36, 24, 21, 9 RESRVD LVCMOS_I/O Reserved. This pin MUST be tied LOW. BIST MODE PINS 27 BISTEN LVCMOS_I Control Pin for BIST Mode Enable (ACTIVE H) BISTEN = L; Default at Low, Normal Mode BISTEN = H; BIST mode active Note: Sequence order for proper function of BIST mode: 1) DS99R421 BISTEN = H. 2) DS99R421 PLL must be locked (10 ms). 3) DS90UR124 PLL must be locked. 4) Select BISTM error reporting mode on DS90UR124. 5) DS90UR124 switch BISTEN from L to H. LVDS SERIALIZER OUTPUT PINS 14 DOUT+ LVDS_O Serializer LVDS True (+) Output. This output is intended to be loaded with a 100Ω load to the DOUT+ pin. The interconnect should be AC Coupled to this pin with a 100 nF capacitor. 13 DOUT− LVDS_O Serializer LVDS Inverted (-) Output This output is intended to be loaded with a 100Ω load to the DOUT- pin. The interconnect should be AC Coupled to this pin with a 100 nF capacitor. POWER / GROUND PINS 5 VDDP1 VDD Analog Power supply, PLL POWER 6 VSSP1 GND Analog Ground, PLL GROUND 9 www.national.com DS99R421 Pin # Pin Name I/O/PWR Description 7 VDDP0 VDD Analog Power supply, VCO POWER 8 VSSP0 GND Analog Ground, VCO GROUND 11 VDDDR VDD Analog Power supply, LVDS OUTPUT POWER 12 VSSDR GND Analog Ground, LVDS OUTPUT GROUND 17 VDDSER VDD Digital Power supply, SERIALIZER POWER 16 VSSSER GND Digital Ground, SERIALIZER GROUND 19 VDDD VDD Digital Power supply, LOGIC POWER 20 VSSD GND Digital Ground, LOGIC GROUND 22 VDDDES VDD Digital Power supply, RECEIVER POWER 23 VSSDES GND Digital Ground, RECEIVER GROUND 25 VDDIN VDD Analog Power supply, LVDS INPUT POWER 26 VSSIN GND Analog Ground, LVDS INPUT GROUND Pin Diagram — DS99R421 30011315 TOP VIEW www.national.com 10 The DS99R421 is a Video Interface converter. It converts an FPD-Link interface (3 LVDS data channels + 1 LVDS Clock, e.g. DS90C365A or equivalent) plus up to three (3) LVCMOS additional signals into a single high-speed LVDS serial Interface (see Figure 11). The 21 bits of data from the FPD-Link Interface are serialized along with the 3 additional over-sampled bits (OS[2:0]) into a randomized, scrambled and DC Balanced data stream to support AC coupling and to enhance the signal eye opening. Four (4) additional overhead bits are sent per clock which provides the embedded clock and serial link control information. The embedded clock LVDS serial stream has an effective data throughput of 120 Mbps (5MHz X 24) to 1.03 Gbps (43MHz X 24). The DS99R421 Line Driver is designed to transmit data up to 10 meters over shielded twisted pair (STP) at signaling rates up to 1.2Gbps (43MHz X 28). The DS90UR124 receiver converts the embedded clock LVDS stream back into a 24-bit wide LVCMOS parallel bus and the recovered low-speed clock. Note: The DS90C124 is not compatible with the DS99R421. DS99R421 LINE DRIVER The DS99R421 output (DOUT±) is used to drive a point-topoint connection as shown in Figure 12. The Line driver transmits data when the data enable pin (DEN) is HIGH, the power down bar (PWDNB) is HIGH, and the device is locked to the incoming FPD-Link stream. If the DEN is set LOW, the device remains locked, but the driver outputs are placed in TRI-STATE. This maybe used to provide a fast start up since a lock time is not required. PRE-EMPHASIS The DS99R421 features a Pre-Emphasis function used to compensate for extra long or lossy transmission media. Cable drive is enhanced with a user selectable Pre-Emphasis feature that provides additional output current during transitions to counteract cable loading effects. The transmission distance will be limited by the loss characteristics and quality of the media. To enable the Pre-Emphasis function, the “PRE” pin requires one external resistor (Rpre) to Vss in order to set the additional current level. Options include: LINK START UP The start up of the DS99R421 involves only one PLL Lock time. The FPD-Link Receiver side must lock to its incoming LVDS RxCLKIN. The Serializer side then extracts its reference clock from the incoming LVDS clock. At the far end of the link, the Deserializer (DS90UR124) also needs to detect the LVDS signals and lock to the incoming serial stream, drives the LOCK pin HIGH, before outputting valid data. Note that when using a Bus Converter (FPD-Link to Serial) additional time is required in the start up to account for the additional PLLs in the path. Normal Output (no pre-emphasis) – Leave the PRE pin open Enhanced Output (pre-emphasis enabled) – connect a resistor on the PRE pin to Vss. Values of the PRE Resistor should be between 6K Ohm and 100M Ohm. Values less than 6K Ohm should not be used. The amount of Pre-Emphasis for a given media will depend on the transmission distance and Fmax of the application. In general, too much Pre-Emphasis can cause over or undershoot at the receiver input pins. This can result in excessive noise, crosstalk, reduced Fmax, and increased power dissipation. For shorter cables or distances, Pre-Emphasis is typically not be required. Signal quality measurements should be made at the end of the application cable to confirm the proper amount of Pre-Emphasis for the specific application. The Pre-Emphasis circuit increases the drive current to I = 48 / (Rpre). For example if Rpre = 15K Ohm, then the PreEmphasis current is increased by an additional 3.2 mA. The duration of the current is controlled to precisely one bit by another circuit. If more than one bit value is repeated in the next cycle(s), the next bit(s) is “de-emphasized”; Pre-Emphasis is turned off (back to the normal output current level, hence output level is also reduced). This is done to reduce power, and to reduce ISI (Inter-Symbol Interference). TYPICAL START UP SEQUENCE 1. FPD-Link Stream is applied to the DS99R421 inputs. 2. With power applied and the DS99R421 enabled, it will lock to the incoming FPD-Link clock. Until the DS99R421 is ready, it will hold its outputs in TRI-STATE. Once the locking is complete, valid serial payloads are sent across the link to the DES (DS90UR124). 3. With power applied and the device enabled, the DS90UR124 will lock to the incoming serial stream. Until the DS90UR124 is locked, outputs are in TRI-STATE and its LOCK output pin is held Low. After Lock, the DS90UR124 outputs are active and LOCK is HIGH. DATA TRANSFER After the link start up, the DS99R421 provides a streaming video interface. For each Pixel Clock (PCLK) received from the FPD-Link Interface 21 bits of information are recovered along with the PCLK. The 21 bits of information include the 18-bits of RGB information and the three video control signals (HS, VS and DE). The over-sample control bits are also sampled in this PCLK domain and appended to the 21 bits of information for a 24-bit total payload. The Serializer side now takes this data and performs four operations to it. First the data is randomized, second the data is scrambled, third the data is balanced, and finally the serial link control and clock embedding is done. The Serializer transmits 28 bits of information per payload to the Deserializer per PCLK. See DS90UR241 datasheet for additional information on the Serializer’s description and operation. The chipset supports PCLK frequency ranges of 5 MHz to 43 MHz. At the 43MHz PCLK rate, 28 bits are sent across the VOD SELECT The Serializer Line Driver Differential Output Voltage (VOD) magnitude is selectable. Two levels are provided and are determined by the state of the VODSEL pin. When this pin is LOW, normal output levels are obtained. For most application set the VODSEL pin LOW. When this pin is HIGH, the output current is increased to increase the VOD level. Use this setting only for extra long cable or high-loss interconnects. OVER-SAMPLED BITS – OS[2:0] Up to three additional signals maybe sent across the serial link per PCLK. The over-sampled bits are restricted to be low speed signals and should be less than 1/5 of the frequency of the PCLK. The DS99R421 OS[2:0] LVCMOS Inputs have wide hysteresis to help prevent glitches. Signals should convey level information only, as pulse width distortion will occur by the over sampling technique and location of the sampling 11 www.national.com DS99R421 serial link at 1.2Gbps. The link is very efficient, sending 25 bits of information (18 RGB, 3 control, 3 over-sample control, and PCLK) with 28 serial bits. This yields 89% efficiency. Functional Description DS99R421 clock. The three over sampled bits are mapped to DS90UR124 bits as: OS0 = bit 21, OS1 = bit 22, and OS2 = bit 23. If the OS bits are not required, internal pull-down will bias the input to a LOW. Receiver Termination Option 3 For high noise environments an additional voltage divider network may be connected to the center point. This has the advantage of a providing a DC low-impedance path for noise suppression. Use resistor values in the range of 100Ω-1KΩ for the pullup and pulldown. Ratio the resistor values to bias the center point at 1.8V. For example (see Figure 15): VDD=3.3V, Rpullup=1KΩ, Rpulldown=1.2KΩ; or Rpullup=100Ω, Rpulldown=120Ω (strongest). The smaller values will consume more bias current, but will provide enhanced noise suppression. COLOR MAPPING Color mapping is application specific. It is very important to properly match the Pixel bit to the correct data channel on the DS90UR124 to properly recover the color and control information. See Figure 11. In this example, the G0 color bit is placed in the RxIN0 channel and is the first bit. The Serializer in the DS99R421 will place this bit as bit number 6. Thus G0 will be recovered by the DS90UR124 on bit 6. The three over sampled bits are mapped to DS90UR124 bits as: OS0 = bit 21, OS1 = bit 22, and OS2 = bit 23. FPD LINK INTERFACE The FPD-Link Interface supports a 3 Data + Clock (21 bit) interface. The interconnect should employ a 100 Ohm differential pair, as termination is provided internal to the DS99R421. Note that color mapping is extremely important to review. Color placement of the bits on the FPD-Link Interface will determine which outputs they will be recovered on. The DS99R421 is expected to reside on the same board as the FPD-Link Serializer (e.g. DS90C365A or GUI with Integrated FPD-Link Serializer). The DS99R421 supports a limited common mode range of 525mV to (VDD – VID/2). Typically this is wide enough to support short interconnects. POWERDOWN (SLEEP) MODE The Powerdown state is a low power sleep mode that the DS99R421 and DS90UR124 may use to reduce power when no data is being transferred. The PWDNB on the DS99R421 and RPWDNB on the DS90UR124 are used to set each device into power down mode, which reduces supply current to the µA range. The DS99R421 enters powerdown when the PWDNB pin is driven LOW. In powerdown, the PLL stops and the outputs go into TRI-STATE, disabling load current and reducing current supply. To powerup, the DS99R421, PWDNB must be driven HIGH. When the DS99R421 exits powerdown, its PLL must lock to RxCLKIN before it is ready for the initialization state. The system must then allow time for initialization before data transfer can begin. @SPEED-BIST (BUILT IN SELF TEST) The DS99R421/ DS90UR124 serial link is equipped with a built-in self-test (BIST) capability to support both system manufacturing and field diagnostics. BIST mode is intended to check the entire high-speed serial link at full link-speed, without the use of specialized and expensive test equipment. This feature provides a simple method for a system host to perform diagnostic testing of both DS99R421 and DS90UR124. The BIST function is easily configured through the 2 control pins (BISTEN and BISTM) on the DS90UR124 and one control pin (BISTEN) of the DS99R421. When the BIST mode is activated, the DS99R421 has the ability to transfer an internally generated PRBS data pattern. This pattern traverses across interconnecting links to the DS90UR124. The DS90UR124 includes an on-chip PRBS pattern verification circuit that checks the data pattern for bit errors and reports any errors on the data output pins on the DS90UR124. The @SPEED-BIST feature uses 2 control pins (BISTEN and BISTM) on the DS90UR124 Deserializer. The BISTEN and BISTM pins together determine the functions of the BIST mode. The BISTEN signal (HIGH) activates the test feature on the DS90UR124. After the BIST mode is enabled on the DS90UR124, toggle the BISTEN pin HIGH on the DS99R421 for the DS90UR124 Deserializer to start accepting data. An input clock signal (RxCLKIN) for the DS99R421 must also be applied during the entire BIST operation. Data on RxIN[2:0] and OS[2:0] are ignored during operation of the BIST. The BISTM pin on the DS90UR124 selects the error reporting status mode of the BIST function. When BIST is configured in the error status mode (BISTM = LOW), each of the ROUT [23:0] outputs of the DS90UR124 will correspond to bit errors on a cycle-by-cycle basis. The result of bit mismatches are indicated on the respective parallel inputs on the ROUT[23:0] data output pins. In the BIST error count accumulator mode (BISTM = HIGH), an 8-bit counter on ROUT[7:0] is used to represent the number of errors detected (0 to 255 max). The successful completion of the BIST test is reported on the PASS pin on the DS90UR124 Deserializer. The DS90UR124 Deserializer's PLL must first be locked to ensure the PASS status is valid. The PASS status pin will stay LOW and then SERIAL INTERFACE The serial link between the DS99R421 and the DS90UR124 is intended for a balanced 100 Ohm interconnect. The link is expected to be terminated at both ends with 100 Ohms and AC coupled. To establish a source termination and the correct levels, a Driver side termination is required. This is typically located close to the device pins and is 100 Ohm resistor connected across the driver outputs. The AC coupling capacitors should be place close to the 100 Ohm termination resistor at both ends of the interface. For the high-speed LVDS transmission, small footprint packages should be used for the AC coupling capacitor. This will help minimize degradation of signal quality due to package parasitics. NPO class 1 or X7R class 2 type capacitors are recommended. 50 WVDC should be the minimum used for best system-level ESD performance. The most common used capacitor value for the interface is 100 nF (0.1 uF) capacitor. The DS90UR124 input stage is designed for AC-coupling by providing a built-in AC bias network which sets the internal VCM to +1.8V. Therefore multiple termination options are possible. Receiver Termination Option 1 A single 100 Ohm termination resistor is placed across the RIN± pins (see Figure 12). This provides the signal termination at the Receiver inputs. Other options may be used to increase noise tolerance. Receiver Termination Option 2 For additional EMI tolerance, two 50 Ohm resistors may be used in place of the single 100 Ohm resistor. A small capacitor is tied from the center point of the 50 Ohm resistors to ground (see Figure 14). This provides a high-frequency lowimpedance path for noise suppression. Value is not critical, 4.7nF maybe used with general applications. www.national.com 12 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 vias 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 range. 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. 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. Termination of the LVDS interconnect is required. For pointto-point applications, termination should be located at both ends of the devices. Nominal value is 100 Ohms to match the line’s differential impedance. Place the resistor as close to the transmitter DOUT± outputs and receiver RIN± inputs as possible to minimize the resulting stub between the termination resistor and device. Applications Information USING THE DS99R421 AND DS90UR124 The DS99R421 allows a FPD-Link based bus to connect to a single-channel serial LVDS interface in a Display using the latest generation LVDS Deserializer (DS90UR124). This allows for existing hosts with FPD-Link interfaces to be further serialized into a single pair and connect with the current generation Display Deserializer. Systems benefit by the smaller interconnect (reduced pins, less size, lower cost). DISPLAY APPLICATION 18-bit color depth (RGB666) and up to 1280 X 480 display formats can be supported. In a RGB666 configuration 18 color bits (R[5:0], G [5:0], B[5:0]), Pixel Clock (PCLK) and three control bits (VS, HS and DE) along with three low speed spare bits OS[2:0] are supported across the serial link with PCLK rates from 5 to 43MHz. TYPICAL APPLICATION CONNECTION Figure 13 shows a typical connection to the DS99R421. The 4 pairs of FPD-Link LVDS interface are the input interface along with the optional over-sampled control signals. Termination of the LVDS signals is provided internally by the DS99R421 device. The single channel LVDS serial output requires an external termination and also AC coupling capacitors. Configuration pins for the typical application are shown: DEN – tie HIGH if unused. PWDNB – Sleep / Enable Control Input – Connect to host or tie HIGH BISTEN – tie LOW if not used, or connect or host VODSEL – tie LOW for normal VOD magnitude (application dependant) PRE – Leave open if not required (have a R pad option on PCB) RESRVD – tie LOW (4 pins) There are 4 power rails for the device. These may be bussed together on a common 3.3V plane. At a minimum, four 0.1uF capacitors should be used for local bypassing. With the above configuration a FPD-Link interface along with three additional low-speed signals are converted to a single serial LVDS channel. LVDS INTERCONNECT GUIDELINES See AN-1108 and AN-905 for full details. • Use 100Ω coupled differential pairs • Use the S/2S/3S rule in separation —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 PCB LAYOUT AND POWER SYSTEM CONSIDERATIONS Circuit board layout and stack-up for the LVDS SERDES 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. 13 www.national.com DS99R421 transition to HIGH once a BER of 1x10-9 is achieved across the transmission link. DS99R421 Functional Overview 30011303 FPD-Link LVDS Input Mapping (3 LVDS Data + 1 LVDS Clock) 30011304 30011305 * Note: bits [0-23] are not physically located in positions shown above since bits [0-23] are scrambled and DC Balanced Single Serialized LVDS Bitstream* FIGURE 11. LVDS Data Mapping Diagram www.national.com 14 DS99R421 30011314 FIGURE 12. AC Coupled Application 30011316 FIGURE 13. DS99R421 Typical Application Connection 15 www.national.com DS99R421 30011317 FIGURE 14. Receiver Termination Option 2 30011318 FIGURE 15. Receiver Termination Option 3 www.national.com 16 DS99R421 Physical Dimensions inches (millimeters) unless otherwise noted Order Number DS99R421QSQ NS Package Number SQA36A 17 www.national.com DS99R421 5-43 MHz FPD-Link LVDS (3 Data + 1 Clock) to Single Embedded Clock DC-Balanced LVDS Converter Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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