DS92LV1021A 16-40 MHz 10 Bit Bus LVDS Serializer General Description The DS92LV1021A transforms a 10-bit wide parallel LVCMOS/LVTTL data bus into a single high speed Bus LVDS serial data stream with embedded clock. The DS92LV1021A can transmit 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 both clock and data bits serially, it eliminates clockto-data and data-to-data skew. The powerdown pin saves power by reducing supply current when the device is not being used. Upon power up of the Serializer, you can choose to activate synchronization mode or use one of National Semiconductor’s Deserializers in the synchronization-torandom-data feature. By using the synchronization 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 DS92LV1021A output pins into TRI-STATE ® to achieve a high impedance state. The PLL can lock to frequencies between 16 MHz and 40 MHz. Features n n n n n n n n Guaranteed transition every data transfer cycle Single differential pair eliminates multi-channel skew Flow-through pinout for easy PCB layout 400 Mbps serial Bus LVDS bandwidth (at 40 MHz clock) 10-bit parallel interface for 1 byte data plus 2 control bits Programmable edge trigger on clock Bus LVDS serial output rated for 27Ω load Small 28-lead SSOP package-MSA Block Diagrams 20026901 TRI-STATE ® is a registered trademark of National Semiconductor Corporation. © 2003 National Semiconductor Corporation DS200269 www.national.com DS92LV1021A 16-40 MHz 10 Bit Bus LVDS Serializer January 2003 DS92LV1021A Block Diagrams (Continued) Application 20026902 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 the clock edge. A start bit and a 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. Functional Description The DS92LV1021A is an upgrade to the DS92LV1021. The DS92LV1021A no longer has a power-up sequence requirement. Like the DS92LV1021, the DS92LV1021A is a 10-bit Serializer designed to transmit data over a differential backplane at clock speeds from 16 to 40MHz. It may also be used to drive data over Unshielded Twisted Pair (UTP) cable. The DS92LV1021A can be used with any of National’s 10-bit BLVDS Deserializers (DS92LV1212A for example) and has three active states of operation: Initialization, Data Transfer, and Resynchronization; and two passive states: Powerdown and TRI-STATE. The following sections describe each active and passive state. Serialized data and clock bits (10+2 bits) are transmitted from the serial data output (DO ± ) at 12 times the TCLK frequency. For example, if TCLK is 40 MHz, the serial rate is 40 x 12 = 480 Mega bits per second. Since only 10 bits are from input data, the serial “payload” rate is ten times the TCLK frequency. For instance, if TCLK = 40 MHz, the payload data rate is 40 x 10 = 400 Mbps. TCLK is provided by the data source and must be in the range of 16 MHz to 40 MHz nominal. The outputs (DO ± ) can drive a backplane or a point-to-point connection. The outputs transmit data when the enable pin (DEN) is high, PWRDN is high, and SYNC1 and SYNC2 are low. The DEN pin may be used to TRI-STATE the outputs when driven low. Initialization Before data can be transferred, the Serializer must be initialized. Initialization refers to synchronization of the Serializer’s PLL to a local clock. When VCC is applied to the Serializer, the outputs are held in TRI-STATE and internal circuitry is disabled by on-chip power-on circuitry. When VCC reaches VCC OK (2.5V) the Serializer’s PLL begins locking to the local clock. The local clock is the transmit clock, TCLK, provided by the source ASIC or other device. Once the PLL locks to the local clock, the Serializer is ready to send data or SYNC patterns, depending on the levels of the SYNC1 and SYNC2 inputs. The SYNC pattern is composed of six ones and six zeros switching at the input clock rate. Control of the SYNC pins is left to the user. 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. Ideal Crossing Point The ideal crossing point is the best case start and stop point for a normalized bit. Each ideal crossing point is found by dividing the clock period by twelve--two clock bits plus ten data bits. For example, a 40 MHz clock has a period of 25ns. The 25ns divided by 12 bits is approximately 2.08ns. This means that each bit width is approximately 2.08ns, and the ideal crossing points occur every 2.08ns. For a graphical representation, please see Figure 9. Resynchronization The Deserializer LOCK pin driven low indicates that the Deserializer PLL is locked to the embedded clock edge. If the Deserializer loses lock, the LOCK output will go high and the outputs (including RCLK) will be TRI-STATE. The LOCK pin must be monitored by the system to detect a loss of synchronization, and the system must decide if it is necessary to pulse the Serializer SYNC1 or SYNC2 pin to resynchronize. There are multiple approaches possible. One recommendation is to provide a feedback loop using the Data Transfer After initialization, the Serializer inputs DIN0–DIN9 may be used to input data to the Serializer. Data is clocked into the Serializer by the TCLK input. The edge of TCLK used to strobe the data is selectable via the TCLK_R/F pin. TCLK_R/F high selects the rising edge for clocking data and www.national.com 2 Powerdown, the PLL stops and the outputs go into TRISTATE, disabling load current and reducing supply current into the milliamp range. To exit Powerdown, PWRDN must be driven high. (Continued) LOCK pin itself to control the sync request of the Serializer (SYNC1 or SYNC2). At the time of publication, other than the DS92LV1210, all other Deserializers from National Semiconductor have random lock capability. This feature does not require the system user to send SYNC patterns upon loss of lock. However, lock times can only be guaranteed with transmission of SYNC patterns. Dual SYNC pins are provided for multiple control in a multi-drop application. Both the Serializer and Deserializer must reinitialize and resynchronize before data can be transferred. The Deserializer will initialize and assert LOCK high until it is locked to the Bus LVDS clock. TRI-STATE For the Serializer, TRI-STATE is entered when the DEN pin is driven low. This will TRI-STATE both driver output pins (DO+ and DO−). When DEN is driven high, the serializer will return to the previous state as long as all other control pins remain static (SYNC1, SYNC2, PWRDN, TCLK_R/F). Powerdown The Powerdown state is a low power sleep mode that the Serializer and Deserializer may use to reduce power when no data is being transferred. The device enters Powerdown when the PWRDN pin is driven low on the Serializer. In Ordering Information Order Number NSID Function Package DS92LV1021AMSA Serializer MSA28 3 www.national.com DS92LV1021A Resynchronization DS92LV1021A Absolute Maximum Ratings @ 25˚C Package: (Note 1) 28L SSOP If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VCC) CMOS/TTL Input Voltage CMOS/TTL Output Voltage 1.27 W Package Derating: −0.3V to +4V 10.2 mW/˚C above +25˚C 28L SSOP −0.3V to (VCC +0.3V) > 2.0kV ESD Rating (HBM) (Note 1) −0.3V to (VCC +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 Continuous Junction Temperature +150˚C Storage Temperature −65˚C to +150˚C Note 1: With a limited Engineering sample size, ESD (HBM) testing passed 2.5kV Recommended Operating Conditions Lead Temperature (Soldering, 4 seconds) Min Nom Max Units Supply Voltage (VCC) 3.0 3.3 3.6 V Operating Free Air Temperature (TA) −40 +25 +85 ˚C Supply Noise Voltage (VCC) +260˚C 100 mVP-P Maximum Package Power Dissipation Capacity Electrical Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Conditions Min Typ Max Units SERIALIZER CMOS/TTL DC SPECIFICATIONS (apply to DIN0-9, TCLK, PWRDN, TCLK_R/F, SYNC1, SYNC2, DEN) VIH High Level Input Voltage 2.0 VCC V VIL Low Level Input Voltage GND 0.8 V VCL Input Clamp Voltage ICL = −18 mA IIN Input Current VIN = 0V or 3.6V −10 ±2 200 270 −1.5 V +10 µA SERIALIZER Bus LVDS DC SPECIFICATIONS (apply to pins DO+ and DO−) VOD Output Differential Voltage (DO+)–(DO−) ∆VOD Output Differential Voltage Unbalance VOS Offset Voltage ∆VOS Offset Voltage Unbalance mV 35 RL = 27Ω 0.78 1.3 V 35 mV −30 −40 mA ±1 ±1 +10 µA +20 µA f = 40 MHz 40 55 mA f = 16 MHz 28 35 mA 88 300 µA IOS Output Short Circuit Current D0 = 0V, DIN = High,PWRDN and DEN = 2.4V IOZ TRI-STATE Output Current PWRDN or DEN = 0.8V, DO = 0V or VCC −10 IOX Power-Off Output Current VCC = 0V, DO = 0V or VCC −20 1.1 mV SERIALIZER SUPPLY CURRENT (apply to pins DVCC and AVCC) ICCD ICCXD Worst Case Serializer Supply Current Serializer Supply Current Powerdown www.national.com RL = 27Ω, Figure 1 PWRDN = 0.8V 4 Over recommended operating supply and temperature ranges unless otherwise specified. Symbol Parameter Min Typ Max Units 25 T 62.5 ns Transmit Clock High Time 0.4T 0.5T 0.6T ns Transmit Clock Low Time 0.4T 0.5T 0.6T ns 3 6 ns 150 ps (RMS) tTCP Transmit Clock Period tTCIH tTCIL tCLKT TCLK Input Transition Time tJIT TCLK Input Jitter Conditions Serializer Switching Characteristics Over recommended operating supply and temperature ranges unless otherwise specified. Symbol tLLHT tLHLT Parameter Bus LVDS Low-to-High Transition Time Bus LVDS High-to-Low Transition Time Conditions Min RL = 27Ω, Figure 2, CL=10pF to GND tDIS DIN (0-9) Setup to TCLK tDIH DIN (0-9) Hold from TCLK tHZD DO ± HIGH to TRI-STATE Delay tLZD DO ± LOW to TRI-STATE Delay tZHD DO ± TRI-STATE to HIGH Delay tZLD DO ± TRI-STATE to LOW Delay tSPW SYNC Pulse Width Figure 7, RL = 27Ω 5*tTCP tPLD Serializer PLL Lock Time Figure 6, RL = 27Ω 510*tTCP tSD Serializer Delay Figure 8 , RL = 27Ω tTCP+1.0 tBIT Bus LVDS Bit Width tDJIT Deterministic Jitter Figure 4, RL = 27Ω, CL=10pF to GND Max Units 0.31 0.75 ns 0.30 0.75 ns 0 ns 4.0 ns Figure 5 ,(Note 4), RL = 27Ω, CL=10pF to GND RL = 27Ω, CL=10pF to GND RL = 27Ω, CL=10pF to GND, (Note 5) Typ 3.5 10 ns 2.9 10 ns 2.5 10 ns 2.7 10 ns ns tTCP + 2.0 2049*tTCP ns tTCP+4.0 ns tCLK / 12 ns f = 40 MHz −320 −110 150 ps f = 16 MHz −800 −160 380 ps Note 1: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation. Note 2: Typical values are given for VCC = 3.3V and TA = +25˚C. Note 3: Current into device pins is defined as positive. Current out of device pins is defined as negative. Voltages are referenced to ground except VOD, ∆VOD, VTH and VTL which are differential voltages. Note 4: Due to TRI-STATE of the Serializer, the Deserializer will lose PLL lock and have to resynchronize before data transfer. Note 5: tDJIT specifications are Guranteed By Design (GBD) using statistical analysis. 5 www.national.com DS92LV1021A Serializer Timing Requirements for TCLK DS92LV1021A AC Timing Diagrams and Test Circuits 20026903 FIGURE 1. “Worst Case” Serializer ICC Test Pattern 20026905 FIGURE 2. Serializer Bus LVDS Output Load and Transition Times 20026907 FIGURE 3. Serializer Input Clock Transition Time 20026908 Timing shown for TCLK_R/F = LOW FIGURE 4. Serializer Setup/Hold Times www.national.com 6 DS92LV1021A AC Timing Diagrams and Test Circuits (Continued) 20026909 FIGURE 5. Serializer TRI-STATE Test Circuit and Timing 20026925 FIGURE 6. Serializer PLL Lock Time, and PWRDN TRI-STATE Delays 7 www.national.com DS92LV1021A AC Timing Diagrams and Test Circuits (Continued) 20026926 FIGURE 7. SYNC Timing Delays 20026911 FIGURE 8. Serializer Delay www.national.com 8 DS92LV1021A AC Timing Diagrams and Test Circuits (Continued) 20026923 For an explanation of the Ideal Crossing Point, please see the Application Information Section. FIGURE 9. Serializer Deterministic Jitter and Ideal Crossing Point HOT INSERTION All Bus LVDS devices are hot pluggable if you follow a few rules. When inserting, ensure the Ground pin(s) makes contact first, then the VCC pin(s), and then the I/O pins. When removing, the I/O pins should be unplugged first, then the VCC, then the Ground. Application Information DIFFERENCES BETWEEN THE DS92LV1021A AND THE DS92LV1021 The DS92LV1021A is an enhanced version of the DS92LV1021. The following enhancements are provided by the DS92LV1021A: • TCLK may be applied before power • TCLK may be halted • Slower typical edge rates help to reduce reflections • PWRDN pin includes an internal weak pull down device TRANSMITTING DATA Once the Serializer and Deserializer are powered up and running they must be phase locked to each other in order to transmit data. Phase locking can be accomplished by the Serializer sending SYNC patterns to the Deserializer, or by using the Deserializer’s random lock capability. SYNC patterns are sent by the Serializer whenever SYNC1 or SYNC2 inputs are held high. The LOCK output of the Deserializer is high whenever the Deserializer is not locked. Connecting the LOCK output of the Deserializer to one of the SYNC inputs of the Serializer will guarantee that enough SYNC patterns are sent to achieve Deserializer lock. While the Deserializer LOCK output is low, data at the Deserializer outputs (ROUT0-9) is valid except for the specific case of loss of lock during transmission. Like the DS92LV1021, the DS92LV1021A is a 10-bit Serializer designed to transmit data over a differential backplane at clock speeds from 16 to 40MHz. It may also be used to drive data over Unshielded Twisted Pair (UTP) cable. USING THE DS92LV1021A The Serializer is an easy to use transmitter that sends 10 bits of parallel TTL data over a serial Bus LVDS link up to 400 Mbps. Serialization of the input data is accomplished using an onboard PLL which embeds two clock bits with the data. RECOVERING FROM LOCK LOSS In the case where the Serializer loses lock during data transmission up to three cycles of data that was previously received can be invalid. This is due to the delay in the lock detection circuit. The lock detect circuit requires that invalid clock information be received 4 times in a row to indicate loss of lock. Since clock information has been lost it is possible that data was also lost during these cycles. When the Deserializer LOCK pin goes low, data from at least the previous three cycles should be resent upon regaining lock. Lock can be regained at the Deserializer by causing the Serializer to resend SYNC patterns as described above. POWER CONSIDERATIONS An all CMOS design of the Serializer makes it an inherently low power device. Additionally, the constant current source nature of the Bus LVDS outputs minimize the slope of the speed vs. ICC curve of CMOS designs. DIGITAL AND ANALOG POWER PINS Digital and Analog power supply pins should be at the same voltage levels. The user should verify that voltage levels at the digital and analog supply pins are at the same voltage levels after board layout and after bypass capacitors are added. 9 www.national.com DS92LV1021A Application Information alizer can be driving from any point on the bus, the bus must be terminated at both ends. For example, a 100 Ohm differential bus must be terminated at each end with 100 Ohms lowering the DC impedance that the Serializer must drive to 50 Ohms. This load is further lowered by the addition of multiple Deserializers. Adding up to 20 Deserializers to the bus (depending upon spacing) will lower the total load to about 27 Ohms (54 Ohm bus). The Serializer is designed for DC loads between 27 and 100 Ohms. The Serializer and Deserializer can also be used in point-topoint configuration of a backplane, PCB trace or through a twisted pair cable. In point-to-point configurations the transmission media need only be terminated at the receiver end. In the point-to-point configuration the potential of offsetting the ground levels of the Serializer vs. the Deserializer must be considered. Bus LVDS provides a plus / minus one volt common mode range at the receiver inputs. (Continued) PCB CONSIDERATIONS The Bus LVDS devices Serializer and Deserializer should be placed as close to the edge connector as possible. In multiple Deserializer applications, the distance from the Deserializer to the slot connector appears as a stub to the Serializer driving the backplane traces. Longer stubs lower the impedance of the bus increasing the load on the Serializer and lowers threshold margin at the Deserializers. Deserializer devices should be placed no more than 1 inch from the slot connector. TRANSMISSION MEDIA The Serializer and Deserializer are designed for data transmission over a multi-drop bus. Multi-drop buses use a single Serializer and multiple Deserializer devices. Since the Seri- Pin Diagram DS92LV1021AMSA - Serializer 20026918 www.national.com 10 Pin Name I/O No. Description DIN I 3–12 Data Input. TTL levels inputs. Data on these pins are loaded into a 10-bit input register. TCLK_R/F I 13 Transmit Clock Rising/Falling strobe select. TTL level input. Selects TCLK active edge for strobing of DIN data. High selects rising edge. Low selects falling edge. DO+ O 22 + Serial Data Output. Non-inverting Bus LVDS differential output. DO− O 21 − Serial Data Output. Inverting Bus LVDS differential output. DEN I 19 Serial Data Output Enable. TTL level input. A low, puts the Bus LVDS outputs in TRI-STATE. PWRDN I 24 Powerdown. TTL level input. PWRDN driven low shuts down the PLL and TRI-STATEs the outputs putting the device into a low power sleep mode. This pin has an internal weak pull down. TCLK I 14 Transmit Clock. TTL level input. Input for 16 MHz–40 MHz (nominal) system clock. SYNC I 1, 2 Assertion of SYNC (high) for at least 1024 synchronization symbols to be transmitted on the Bus LVDS serial output. Synchronization symbols continue to be sent if SYNC continues asserted. TTL level input. The two SYNC pins are ORed. DVCC I 27, 28 Digital Circuit power supply. DVCC voltage level should be identical to the AVCC voltage level. DGND I 15, 16 Digital Circuit ground. Ground potential should be the same as AGND. AVCC I 17, 26 Analog power supply (PLL and Analog Circuits). AVCC voltage level should be identical to the DVCC voltage level. AGND I 18, 25, 20, 23 Analog ground (PLL and Analog Circuits). Ground potential should be the same as DGND. Truth Table DIN (0–9) TCLK_R/F TCLK SYNC1/SYNC2 DEN PWRDN DO+ DO− X X X X X 0 Z Z X X X X 0 1 Z Z X X SYSTEM CLK 1∼ 1 1 SYNC PTRN SYNC PTRN* DATA 1 L 0 1 1 DATA (0–9) DATA (0–9)* DATA 0 K 0 1 1 DATA (0–9) DATA (0–9)* RI RI− RCLK_R/F REFCLK REN PWRDN RCLK LOCK X X X X X 0 Z Z X X X X 0** 1 Z Z SYNC PTRN SYNC PTRN* X SYSTEM CLK 1 1 CLK 1† DATA (0–9) DATA (0–9)* 1 SYSTEM CLK 1 1 L 0 DATA (0–9) DATA (0–9)* 0 SYSTEM CLK 1 1 K 0 ∼ Pulse 5-bits * Inverted †Must be 1 before SYNC PTRN starts ** Device must be locked first 11 www.national.com DS92LV1021A Serializer Pin Description DS92LV1021A 16-40 MHz 10 Bit Bus LVDS Serializer Physical Dimensions inches (millimeters) unless otherwise noted Order Number DS92LV1021AMSA NS Package Number MSA28 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. 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