Ddr3 length matching tolerance

I am currently routing a memory interface between a XC7K160T-2FFG676I and four DDR3 x16 devices (PN: MT41K256M16TW-107). So the diff. From SOC to 1st DDR3 memory chip: 2165 mils. Inter-pair skew is used to This spacing is referred to as the 5W rule. \$\endgroup\$ – SteveSh Jun 22, 2021 · Length matching. frequency can be reduced to a single metric using an Lp norm. Is it necessary to match length these signals? I realize that Altium designer do not include this signals when using the xsignal wizard, on the other hand, I have taken a look some designs and some of them has RESET and CKE matched with Aug 22, 2023 · Compensating for unbalanced via count in DDR3 routing. This video includes also explanation about setting up rules, T-Points and how to do length matching of individual branches / segments. However my understanding is that each Byte Lane Group (DQ, DQS & DM) must be matched within Length matching takes place via a simple select and match user interface. At -55°C the length increases by 26°; at +125°C it increases by 57°. I believe I have a good understanding of the length matching rules within byte groups and address/command/control signals as well as between the byte groups and A/C/C signals. Depending on the characteristic impedance throughout varying sections of the board, a mistmatched length-matching could create additional timing or signal quality issues. The longer the cable assembly, the more difficult is the matching task. The matching requirements are dependent on the target data rate, FPGA, and memory device and must include both PCB trace delay and package delay. Let's take another case, a differential line. Here is link to the fil Jul 16, 2016 · Hi @tuandt, yes, you should take that into the length matching consideration. Timing Considerations hing, your design will go probably directly to the trash. Dec 22, 2020 · Length matching is performed mainly to avoid the skew generated among the parallel data lines/data bus width. DDR3 x16 Byte Group Length Matching. 4. 0 high speed, but the lessons also apply to USB 3 Gen 1 and Gen 2. This spacing is referred to as the 5W rule. 3. Synchronous. 3 Internet access topology. Mar 17, 2022 · The first rule defines the pair-to-pair length matching requirements, and has the Constraint set to Group Matched Lengths. VTT Termination Use the following guidelines for VTT termination. These memories have clock speeds reaching 1066 MHz and support up to 24 GB of memory. All groups and messages Apr 8, 2020 · PCB trace length matching is exactly as its name suggests: you are matching the lengths of two or more PCB traces as they are routed across a board. 3041 mm of allowed length mismatch. Incidentally, analog signal integrity may be a bigger problem than digital in this design. Does anyone have a clear rule for clock length matching in the case of DDR3 without write leveling ? Thanks! marguedas CK_t - 20 ps CK_t + 20 ps Route all addresses and commands to match the clock signals to within ±20 ps to each DDR4 component Data Bus within the byte lane group (DQS, DQs, DMs) DQS0_t - 10 ps DQS0_t + 10 ps Match in length all DQ, DQS, and DM signals within a given byte-lane group with a maximum deviation of ±10 ps. a maximum trace/ cable length which is specified in the various specifications. STM32MP1 Series memory interface can address different types of memory: DDR3 and DDR3L with a data rate speed at 1066 Mbps, voltage at 1. When this Constraint option is used, the software will detect all Jul 22, 2020 · To set impedance constraints for a net group, open the Electrical Constraint Set option and navigate to Routing → Impedance. <br>Okay, now you do the same thing on an entire byte lane and Altium says that all the signals of the byte lane have the same Jan 4, 2023 · If I make a cable manually to connect the USB3. The maximum allowed trace length for DDR signals is 2 inches. Mar 4, 2014 · The impedance matching resistors differential signal is always at 100 Ohms. May 5, 2019 · Differential Pair Length Matching: Best Practices for Signal Integrity Conceptually, differential pairs are very simple, being just a pair of equal and opposite polarity signals running on two parallel conductors. (I am not including Fan out Stub here) Flight Time = length * propagation delay => 1. The PWR wires can be defined according to the PWR and AWG. Preferably, the length of the clock trace should be somewhere in between. Also as you mentioned, sometimes it might be benefitial if the inside package length matching is quite bad, approaching the limits. 15mm of unmatched length causes ~1ps of skew. Communication signals operate at different frequencies, and you’re able to get the clock period by inverting the frequency value. For example, match the trace length of the DMC_CK and /DMC_CK signals within +/- 10 mils relative to each other. The topology of the serpentine segments is fully Apr 27, 2012 · SO-DIMM DDR3 Length Matching Diagram. Route clock signals. Again, this ideal length for the clock is calculated by subtracting the tolerance (or most of it) from the longest trace once everything is optimized. This parameter is termed as the propagation delay. The caveat is that any editing of the clock or the traces on the edge of the tolerance band is likely to upset All groups and messages Jun 25, 2016 · Hello, I am designing my own board based on the am3358 and one ddr3 chip. In this case, length matching is done for the data lines and DQS lines within a group. The DDR3/DDR3L data group signals Nov 27, 2012 · DDR3 Layout Length Matching. When placing signal vias, it is recommended to place ground, or return, vias close by in order to provide a short path to ground. This includes the ability to have track segments in multiple match groups which is needed for Sep 18, 2019 · This video explains the most common layout topics for USB signals: impedance, trace length and matching, and printed circuit board (PCB) stack-up. According to AR # 46132, these trace matching rules must be followed:-Any DQ and its associated DQS / DQS #-Any Address and Control signal and the corresponding CK / CK #-CK / CK # and DQS/DQS # It seems there is a problem! The three rules imply that all signals must be of the same length! I think there is a problem in the last rule. 6 Altium Tutorials for newbies April 27, 2012. 5-V supply rail (±5% maximum AC/DC tolerance) simplifies the overall design, and reduces the differential between the two devices and minimizes the need for additional layers (power) in the end-use application. 5 to 17. It is hard to keep the wires the same length. Data, Data mask and Data strobe Signals. That is one of the reasons why we normally length match ADDR/CMD/CTL signals more precisely than specified in design guide, so we are sure, that even if the difference between H4 and H5 is applied, the signals in the ADDR/CMD/CTL group are still routed withing the required tolerance. Dec 21, 2020 · For the stripline I’ve simulated above, this would equate to 1. Cost. Apr 8, 2020 · This leaves a lot of room for length tuning margin. Add a comment. pair length equalization to 2-3mm is not an issue. Do we need to length match Data strobe Nov 7, 2019 · A DDR3 SDRAM on a DIMM package has 240 pins while the microprocessor that connects to the memory chips has larger pin counts. Then go through and set the matched length rules for each class (ie address would have a 20ps match length. g. it will delay the sampling point for the signals in each DQ group to match the length of the CA signals for that IC. 50 Ohm characteristic. 5mm more for addr class. As both net groups are part of a DDR3 interface, the impedance of the traces on this interface should be set to 34 Ohms. May 9, 2013. Clock (fly-by): From SOC to 1st DDR3 memory chip: 2287 mils. I don't know which one to follow in my particular case. BGA package (e. In this particular example, DQ2 is the Target and DQ0, DQ1, and DQ3 must be length matched based on the routed length of DQ2. The caveat is any editing of the clock or traces on the edge of the tolerance band is likely to upset the Sep 27, 2016 · Physical length or the Timing. Aug 16, 2016 · hing, your design will go probably directly to the trash. Apr 1, 2019 · The PCIe design guidelines and standards define up to 16 available lanes, which also define the size of standardized PCIe card slots. 37 mil/mm) = 591 mil. At 30°C, the length decreases by only 0. 3 Differential Signal Length Matching. Route all addresses and commands to match the clock signals to within ±20 ps to each discrete memory component. delaying the outgoing data transfer in each group to match the CA timing), then you should also 10 mils. May 16, 2018 · How to do DDR3 T-Branch Length Matching (Cadence Allegro) Watch on. The length matching requirements (Tables 5-66 and 5-67) have been derived based on a large variety of designs and simulations. Place a 0. BGA package. Jan 9, 2020 · Double data rate three (DDR3) is a type of dynamic random-access memory (DRAM) that succeeds earlier generations of DDR. The full range of the traces is 18. Try not to push your luck to the boundary with inconsistent layout and length matching. 3 High-Speed Signal Trace Length Matching Match the etch lengths of the relevant differential pair traces. Mar 3, 2022 · Can you provide some of the major requirements such as diff Z tolerance, length matching, etc. Routing can be simplified by swapping data bits within a byte lane if needed. The trace length/matching guidelines are available in the Virtex-6 Memory Interface Solutions User Guide (UG406); seethe DDR2 and DDR3 Memory Interface Solution -> Design Guidelines -> Trace Lengths section: http Mar 1, 2009 · The room temperature phase shift is 80,345°. Supose you are escaping a trace from a processor BGA ball (Layer 1), now the trace will go trough a via from Layer 1 to layer 3 and then will pass again trough a via to layer 1 and finally to a DDR3 chip ball. 11-26-2012 10:06 PM. Supply and ground planes, routing and decoupling should be checked insure optimal voltage/current supply for DDR3 devices. Aug 6, 2017 · Let's take DDR4. It's best to play it safe and just timing match as close as possible across the bus. The Q is just some ancient notation. Interface type. Consult the AC timing section of the SDRAM datasheet to find out the maximum allowable skew across signal lines. Mar 11, 2023 · In this article, we will provide a comprehensive guide to DDR3 PCB design and routing, including timing, impedance matching, signal names, grouping, and flyby techniques. For DDR3 routing, better to follow these steps. May 11, 2017 · 103 7. Nov 15, 2022 · This diagram is probably helpful when understanding DDR3 matching, the lengths and tolerances will be different for the STM32 but the overall idea is the same The maximum length of the first SDRAM to the last SDRAM must not exceed 0. Jun 18, 2015 · I saw in other documents various rules for clock routing (up to 1000mil tolerance). Also, maintain a minimum keep-out area of 30 mils to any other signal throughout the length of the trace. Figure 2-3. MIG 7 Series includes specific trace matching requirements between CK/Addr, DQ/DQS and CK/DQS. 1. If you’re a PCB designer, you don’t need to perform this calculation manually, and you just need to use the right set Also, looks like Altium does not account for vias length, so length tolerances might be +-1. In this paper, we look at the length matching between clock and command/address/control (CAC) on daisychained signal routing for memory-down DDR3 and DDR4 DRAM. Aug 13, 2019 · PCB trace length matching is crucial for high frequency synchronous signals. However, I do not see anything like that. These guidelines can differ from vendor to vendor. It looks like length tuning tools only exist for differential pairs. 4. The second rule is to ensure the nets within each differential pair are within tolerance, and has the Constraint set to Within Differential Pair Length. The requirements have been distilled down to a set of layout and routing rules that allow designers to successfully implement a robust design for the topologies TI supports. In summary, we’ve shown that PCB trace length matching vs. An example comes from DDR, where the differential strobe (DQS) and differential clock lines need to have length matching enforced. 5Gbps signals. Clamshell Topology. Data signals are called DQ and data strobe is DQS. It would be appreciate it if you could tell how to calculate the required length matching between Mar 10, 2017 · veral questions. Intra Pair Length Mismatch Tolerance For 12. com/ This video explains one of possible techniques used for DDR2 / DDR3 length matching in Altium Designer. You can find same recommendation in Micron reference design (I don't recall what exact UG it was, sorry) answered. In this way, routes can quickly be matched against each other or set to a specified distance. I looked at the bbb project to have a example of layout and i have a question about length matching for the ddr3 interface. PCIe devices use embedded clocking with different line codes (8b/10b in Gen The MIG Virtex-6 DDR2/DDR3 design requires that specific trace matching guidelines be followed to ensure proper behavior in hardware. To view the matching requirements (including derating values), please refer to the DDR3 In this tutorial, I have discussed #LPDDR4 SDRAM and its #Length #Matching supported by Altium designers 21 and 22 in very detail. Jun 14, 2016 · The tolerance should be specified by the manufacturer of the FPGA you are using. 0 includes a phase tuning tool for differential pairs, I thought it might also include a tool for length matching single-ended traces (e. Dec 7, 2018 · When working with DDR3 and DDR4 routing, the fly-by topology begins with the controller, starts with Chip 0, and routes through Chip N—or the upper data bit. DDR3 data/address/strobes). , TFBGA) or TSOP. 7. 4 in trace in inner layer (L3) with two vias of length 12 mils each from Top layer to L3. Yes (very generous, ~400-500 mils tolerance in some products) Yes. It is bidirectional signal. e. Length Matching Rules. But it is said we can have length matching tolerance of "\+/-"300 mils in ug388. In terms of signal integrity, differential pair routing becomes progressively more difficult when frequencies get higher. Best picture I have ever seen to Length matching of tracks is an essential step in ensuring correct timing at the signal receiver for high speed transmissions. Nov 17, 2019 · However, you might need to apply delay tuning/length matching between two differential pairs. Proteus PCB Design includes support for automatic length matching of tracks via a simple select and match user interface. Match the etch lengths of the relevant differential pair traces. Set the delay tolerance for each class. These traces could be one of the following: Multiple single-ended traces routed in parallel. It is transmitted by the same component as the data signals. 2. Since Diptrace 3. For example, in a DDR3/4 memory interface: each of the eight bits of data has an associated data strobe, as well as a differential clock. 25 mm) for the signals withing a group and 0. In short, you don't need length matching for termination resistor traces but you should keep this length minimum, maximum of 300mils is recommended. Each data byte has their own strobe. 50ps of skew is acceptable in most STM32 SDRAM PCB layouts, but lower the skew – the better it is. Not too tricky. The basic idea of this length matching is that the shorter trace follows a detour or meander in order to lengthen it to match the length of the longer trace. Figure 1: four-and six-way PCB stack. Oct 23, 2023 · My suggestion would be to create a DDR3 class, a clock class, an address class, and a data class. 5e11 mm/s)* (100 ps)* (39. Sep 2, 2022 · This length matching is constrained by the length of the clocking signal and the rise time of the signals traveling on the bus. Jul 31, 2016 · Length Matching. Again, this ideal length for the clock is found by subtracting the tolerance (or most of it) from the longest trace once everything is optimized. It is recommended that the KeyStone DSP DDR3 interface and SDRAM share a common 1. Intra-pair skew is the term used to define the Mar 23, 2022 · The full range of the traces is 18. Here is a summary of the DDR3 PCB layout length matching Jul 2, 2019 · High-speed DDR3 and DDR4 memory requires tight length matching between clock and data traces so that signal timing parameters can be met. Terminations from last DDR3 chip are all less than 500 mils. Lets say i have a 1. Feb 26, 2009 · Other signals- Address and control signals should match in length according to DDR Clock signal. With that, the amount of data and speed of its transfer mean the world. We are doing the Address,cmd and ctrl lines length matching tightly with clock pair and data byte with data mask and strobe tight length matching. The following sections discuss considerations for length matching. As an example, for DDR3, the allowed skew between these differential pairs is 5 ps according to Intel's guidelines. As with all high-speed signals, keep total trace length for signal pairs to a minimum. Length of the Cable Assembly. Aug 21, 2017 · Therefore the edge rate can be about 400 ps, so 100 ps difference wouldn't make much of a shift in eye crossover position. Depending on the module of the DDR3 SDRAM, the data rate ranges from 400 MHz to 1066 Mhz. Each end of a differential pair. I think I should also take care of the wire length of the differential pairs. And the 100ps would be equal to 15-20 mm in trace length difference, which is huge. 1uF cap and 0. fedevel. Different host controllers will have different numbers of lanes available, which can then define how many peripherals they can support. Data and DQS lines with similar length will undergo similar propagation delay on the PCB trace. The other module type is DIMM or dual in-line memory modules (288-pins) that are in use in devices like desktops and servers. I am able to compensate the length tolerance by Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Jul 26, 2019 · To sum up, high speed PCB design is applied to devices with PCBs working at high frequencies with the use of high speed interfaces. Standard values that I am using are something like withing 0. In addition, the tool can run a memory stress test to verify the DDR3 functionality as well as the reliability. This high clock speed and large storage capacity ensured DDR3 remained a mainstay in modern computing, but it was eventually improved to DDR4. DDR2 CLK vs DSQ vs ADR length matching. Best picture I have ever seen to explain memory length matching requirements between Memory controller and SO-DIMM socket. For DDR3/3L, VTT termination is recommended by JEDEC, as this Apr 12, 2019 · Hi, I am using iMX6 Dual lite processor, In which DDR3 we are doing the layout 4 DDR3 chips with Fly-by topology. By the memory controller on write and the by the memory on read commands. MX6 chips often run the DDR3 at speeds less than 500 MHz, the chips allow some more relaxation in length matching because of their high slew rate IOs meant for 1+ GHz bus operation. For example, let us suppose that we have a timing window of 100 ps; if we have loosely spaced traces in a differential pair routed as striplines on the Dk = 4 substrate, then the allowed length match will be: ΔL = (1. This picture illustrates a part of high speed PCB design developed by our engineers for a home automation system. x86 Motherboard Development Process – Step by Step July 12, 2012. 1 mm between the positive and negative signal in the pair). 35 V for DDR3L. The following are general guidelines for PDN development in DDR3 board designs. Apr 4, 2015 · Signals on an FR4 PCB travel at approx half the speed of light, so you'd want to make your longest trace no more than 44 mm longer than the shortest trace. I am laying out a DDR3 memory based on 4x 16bit chips and have seen in EMI Handbook Vol 2, Chap 4, Table 4-23 that "data, address and command signals must have matched length traces to within +/-250mil". All the high speed PCB design guideline suggest performing length matching with the clock trace length as the target length and trace length tolerance of the data, address, command lines has to be maintained with respect to clock signal. Clocks should maintain a length-matching between positive ( p) and negative ( n) signals of ±2 ps, routed in parallel. 0 signals and PWR. 1 Signal Length Matching Signal length matching is a two-fold item for the board designer. 5 tCK for DDR4. Have a look and think about that. Routing occurs in order by byte lane numbers, and data byte lanes are routed on the same layer. Solid Power and Ground planes should be used in DDR3 routing areas. pcb. 8mm pitch) FPGA Chip is XC6SLX45T in 484ball BGA (1mm pitch) UPD2: Dark red traces at L6 is vref net. First, it can perform calibrations for DDR3 to match the MMDC PHY delay settings with PCB for optimal DRAM performance. Description. This video includes also explanation about setting up rules and how to do length matching of individual branches / segments. . I've routed DDR3 with +/-1mm without problems. 01uF as close as possible for every VDDQ pin. Matchgroup tolerances are easily set up and the internal signal distances can be added to the components for improved accuracy. The goal of this document is to describe how to make the AM65x/DRA80xM DDR system implementation straightforward for all designers. Since of the core thickness of approx. If the controller does not also support write leveling (i. Jun 6, 2018 · People often use much tighter length matching just because it doesn't hurt - many times it's not necessary though. 1mm, the signals routed on L4 are about 2mm longer than the ones routed on L3. Both address & control group signals are length matched. Routing distance in between eacg DDR chip is 492 mils (applies for address, control and clock). Figure 2-3 shows an example. 2. Package. 5mm, with the clock straddling the difference. The following topics provide guidance on length matching for different types of SDRAM signals. The reason for length matching in this case is because of TIMING. 8° making thermal control during the phase match operation less critical. I am able to compensate the length tolerance by The AM335X Datasheet, Rev. As you’re probably aware, signals travel on PCB traces with a certain speed. DDR4 DRAMs can operate with either clamshell topology or fly-by topology. DDR3 interface layout. 4*175 = 245ps. The examples we provide focus on USB 2. 0. So here is Unless explicitly defined, the tool will arbitarily assign one of the nets as the "Target" and all other nets within the Match Group will be expected to be routed within the tolerance specified. For DDR2 and DDR3, which signal DQ, DM and DQS are point to point interconnect , so no topology, however, outside the column is not in the multi-rank DIMMs (Dual In Line Memory Modules) design such . F, Section 5. Data strobe is the clock signal for the data lines. Total Length = Trace Length + 2 * Via Length. Also a link to a reference for that interface would be helpful. The image below shows the two net groups defined in this board. We will include the compensation for the via length as the signal traces are often routed on Because of this, most DDR2 design guides recommend that clock signals be routed at the same length or longer than the address, control, and command signals to compensate for this timing variation" So, this means clock should not be smaller than address/control lines. So-DIMM or small outline dual in-line memory modules (260-pins) that are in use in portable computing devices like laptops. For trace length requirements for each protocol and device, see later sections in this document. Intra-pair skew is the term used to define the difference between the etch length of the + and - lane of a differential pair. The purpose is to provide customers with a relatively easy and reliable approach to successful DDR3 design. pcb-design. 5 mm (+/- 0. 5 mm with the clock straddling the difference. <br>Okay, now you do the same thing on an entire byte lane and Altium says that all the signals of the byte lane have the same Nov 30, 2011 · http://www. 5-V supply rail. Interface Termination All of the DDR interface signals without ODT require external termination for improved signal integrity. Impedance. Depends on controller drive strength, also there are differential pairs. 6. A common 1. Dec 8, 2021 · The DDR3 controller will pretty much always support read leveling, i. In particular, the transit time of signals often needs to be synchronized by matching the copper length of the traces on the PCB. For different DIMM configurations, check the appropriate JEDEC specification. Apr 30, 2021 · Because DDR3 chips are almost always meant to operate at higher than 1GHz (higher speed grade), and the i. #1 by skrasms » 31 Jul 2016, 20:24. Multiple differential pairs routed in parallel. 3. More information on DDR3 SDRAM can be found on JEDEC DDR3 SDRAM Standard JESD79-3F. ABSTRACT. If you have channels then create a clock class, address class and data class for each channel. 5 V for DDR3 and. UPD: DDR3 Chip is MT41J64M16LA in 96ball FBGA (0. Jan 1, 2022 · According to AR # 46132, these trace matching rules must be followed:-Any DQ and its associated DQS / DQS #-Any Address and Control signal and the corresponding CK / CK #-CK / CK # and DQS/DQS # It seems there is a problem! The three rules imply that all signals must be of the same length! I think there is a problem in the last rule. For complete course click Jun 15, 2017 · I have a question about length matching of the CKE and RESET signals in a DDR3 BUS using a flyby topology. 3 gives all the information necessary for successful DDR3 design. How the length matching has been done if different layers are used? The signal on the outer layers doesnt travel at the same speed as the inner layers. Configuring the meander or serpentine style in the Proteus Jun 20, 2018 · Some datasheets will specify something like 1 mm length tolerances, which equates to several ps of timing margin between signals. 6. Low (About $5) Can be high example, match the trace length of the DMC_CK and /DMC_CK signals within +/- 10 mils relative to each other. The process is fully automatic, and therefore the customers can get there DDR3 working in much shorter time. Even at its lowest frequency, you’ll be dealing with high-speed signals on a limited amount of PCB space. Address and control signals and. Nov 20, 2019 · DDR4 or Double Data Rate 4 comes in two distinct module types. Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Mar 10, 2017 · veral questions. A PCB design with a calculated trace width of 6 mils requires a minimum of 30 mils spacing between high-speed differential pairs. <br>My stackup from L1 to L6 is as follows: signal - GND - signal - signal - PWR - signal<br>The byte net classes are routed on separate layers (L3 and L4), but the address control bus is routed on both L3 and L4. 2 mm withing a differential pair (+/- 0. 69 tCK for DDR3 and 1. rr cy vw df zl fu ot jz zm ee