Note that these guidelines apply whether you route through an edge connector to a SODIMM card or directly to modules mounted on a PCB. The image below shows the various signals involved in DDR4 routing between a controller (CPU, FPGA, etc.) and DRAM modules. However, you will still want to match the driver impedance to the trace impedance and terminate appropriately. This is because many modules and controllers will use on-die termination so that the termination impedance at the various pins can be adjusted.
If you start searching for impedance values and signal functions in DDR4 modules, it can be difficult to find consistent answers.
DDR4 Routing and Design Rulesīefore you route a single trace on your DDR4 bus, it's critical to know the functions of each signal and their impedance values. If you're just getting started learning about DDR routing or you need to get a quick refresher, we've compiled the essential DDR4 routing guidelines in this article for your reference. In fact, now that DDR5 and DDR6 are on the horizon, having a solid foundation in DDR4 routing guidelines will give you a head start if you ever plan to use these more powerful memories in your system. DDR4 RAM also featured improved data integrity with the addition of cyclic redundancy checks on write data and on-chip parity detection. With notable improvements in speed, performance, and bandwidth, DDR4 memory deserves special attention.ĭDR RAM devices can be a difficult to work with due to the large number of signals that must be routed on a PCB or SODIMM card, but these memory devices are not going away anytime soon. In 2014, the fourth-generation of DDR RAM (DDR4) was introduced, offering reduced power consumption, increased data transfer speeds, and higher chip densities.
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