Technical Note. e MMC PCB Design Guide. Introduction. TN-FC-35: e MMC PCB Design Guide. Introduction

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1 Introduction Technical Note e MMC PCB Design Guide Introduction This document is intended as guide for PCB designers using Micron e MMC devices and will discuss the primary issues affecting design and layout. Figure 1: e MMC 4.5 and 5.0 Package Compatibility A DAT0 DAT1 DAT2 A A DAT0 DAT1 DAT2 B DAT3 DAT4 DAT5 DAT6 DAT7 B DAT3 DAT4 DAT5 DAT6 DAT7 B C V DDIM Q C V DDI Q C D D D E E E F F F G G G H H DS H J J J K K K L L L M N Q CMD Q CLK M CMD CLK M P Q Q N Q Q N P Q Q P Ball e MMC 4.51 e MMC 5.0 Comment H5 DS DS can be floating if HS400 is not used. A6, J5 can be floating if HS400 is not used. C5 Used for routing in this technical note only because it is internally, and JEDEC redefined it as for e MMC Products and specifications discussed herein are for evaluation and reference purposes only and are subject to change by Micron without notice. Products are only warranted by Micron to meet Micron's production data sheet specifications. All information discussed herein is provided on an "as is" basis, without warranties of any kind.

2 Introduction Figure 2: Host to Micron e MMC 5.0 Connection C1 C2 R_CMD R_DAT R_DAT R_DAT R_DAT R_DAT R_DAT R_DAT R_DAT R_ U1 e MMC CLK CMD DS SR_DS SR_CLK CLK CMD DS U2 Host controller C5 V DDiM C6 V DDiM C3 GND DAT0 DAT1 DAT2 DAT3 DAT4 DAT5 DAT6 DAT7 R_DS DAT0 DAT1 DAT2 DAT3 DAT4 DAT5 DAT6 DAT7 GND C4 2

3 Important Notes and Warnings Micron Technology, Inc. ("Micron") reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions. This document supersedes and replaces all information supplied prior to the publication hereof. You may not rely on any information set forth in this document if you obtain the product described herein from any unauthorized distributor or other source not authorized by Micron. Automotive Applications. Products are not designed or intended for use in automotive applications unless specifically designated by Micron as automotive-grade by their respective data sheets. Distributor and customer/distributor shall assume the sole risk and liability for and shall indemnify and hold Micron harmless against all claims, costs, damages, and expenses and reasonable attorneys' fees arising out of, directly or indirectly, any claim of product liability, personal injury, death, or property damage resulting directly or indirectly from any use of nonautomotive-grade products in automotive applications. Customer/distributor shall ensure that the terms and conditions of sale between customer/distributor and any customer of distributor/customer (1) state that Micron products are not designed or intended for use in automotive applications unless specifically designated by Micron as automotive-grade by their respective data sheets and (2) require such customer of distributor/customer to indemnify and hold Micron harmless against all claims, costs, damages, and expenses and reasonable attorneys' fees arising out of, directly or indirectly, any claim of product liability, personal injury, death, or property damage resulting from any use of non-automotive-grade products in automotive applications. Critical Applications. Products are not authorized for use in applications in which failure of the Micron component could result, directly or indirectly in death, personal injury, or severe property or environmental damage ("Critical Applications"). Customer must protect against death, personal injury, and severe property and environmental damage by incorporating safety design measures into customer's applications to ensure that failure of the Micron component will not result in such harms. Should customer or distributor purchase, use, or sell any Micron component for any critical application, customer and distributor shall indemnify and hold harmless Micron and its subsidiaries, subcontractors, and affiliates and the directors, officers, and employees of each against all claims, costs, damages, and expenses and reasonable attorneys' fees arising out of, directly or indirectly, any claim of product liability, personal injury, or death arising in any way out of such critical application, whether or not Micron or its subsidiaries, subcontractors, or affiliates were negligent in the design, manufacture, or warning of the Micron product. Customer Responsibility. Customers are responsible for the design, manufacture, and operation of their systems, applications, and products using Micron products. ALL SEMICONDUCTOR PRODUCTS HAVE INHERENT FAIL- URE RATES AND LIMITED USEFUL LIVES. IT IS THE CUSTOMER'S SOLE RESPONSIBILITY TO DETERMINE WHETHER THE MICRON PRODUCT IS SUITABLE AND FIT FOR THE CUSTOMER'S SYSTEM, APPLICATION, OR PRODUCT. Customers must ensure that adequate design, manufacturing, and operating safeguards are included in customer's applications and products to eliminate the risk that personal injury, death, or severe property or environmental damages will result from failure of any semiconductor component. Limited Warranty. In no event shall Micron be liable for any indirect, incidental, punitive, special or consequential damages (including without limitation lost profits, lost savings, business interruption, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on tort, warranty, breach of contract or other legal theory, unless explicitly stated in a written agreement executed by Micron's duly authorized representative. Signal and Capacitor Placement TN-FC-35: e MMC PCB Design Guide Important Notes and Warnings SR_CLK should be close to the host device, and SR_DS should be close to the e MMC device. e MMC signals can be fanned out through pins. No internal connection is present for pins. Micron recommends that e MMC signals not be fanned out through pins. 3

4 The recommended decoupling capacitors should be placed on the bottom side of the PCB across the BGA escape vias in order to minimize the connection inductance seen by the capacitor. The capacitor pad should be connected to the power and ground plane with a larger via to minimize the inductance in decoupling capacitors and allow for maximum current flow. The recommended capacitor values are shown in Table 1 (page 6). Wide, short traces between the via and capacitor pads should be used, or the via placed adjacent to the capacitor pad. Figure 5 (page 6) shows how to connect capacitor pads to the power and ground plane. Method 1 is not recommended, while the others are recommended. Figure 3: Capacitor Placement and Signal PCB Layout 153-Ball TN-FC-35: e MMC PCB Design Guide Signal and Capacitor Placement D0 D1 D2 D3 D4 D5 D6 D7 V DDi Q DS CMDCLK 4

5 Figure 4: Capacitor Placement and Signal PCB Layout 100-Ball TN-FC-35: e MMC PCB Design Guide Signal and Capacitor Placement V DDIM Q Q DAT0 DAT2 DS DAT5 DAT7 Q Q Q Q DAT1 DAT3 DAT4 DAT6 Q CMD CLK Q 5

6 Signal and Capacitor Placement Table 1: Component Parameter Values Parameter Symbol Min Max Recommended Unit Comments Pull-up resistance for CMD R_CMD KΩ To prevent bus floating Pull-up resistance for DAT[7:0] R_DAT KΩ To prevent bus floating Pull-up resistance for R_ KΩ It is not necessary to put pull-up resistance on line if the host does not use H/W reset. Pull-down resistance for R_DS R_DS KΩ Impedance of CLK/CMD/DS/ DAT[7:0] Ω Impedance match Serial resistance on CLK line SR_CLK Ω To stabilize CLK signal Serial resistance on DS line SR_DS Ω To stabilize DS signal capacitor value C1, C µf Decoupling capacitor should be connected with and Q as closely as possible. capacitor value ( 8GB) C3, C µf Decoupling capacitor should be capacitor value (>8GB) µf connected to and as closely as possible. V DDIM capacitor value C5, C µf Decoupling capacitor should be connected to V DDIM and Q as closely as possible. Figure 5: Connecting Capacitor Pads Unacceptable 1 Acceptable 2 Good 3 Better 4 Best 5 (Solid via within pad) 6

7 PCB Topology and Layout Figure 6: Transmission Line Topologies The PCB board must have at least four layers. TN-FC-35: e MMC PCB Design Guide PCB Topology and Layout CLK, CMD, DQ and DS signals should be treated as transmission lines with controlled impedance from 45Ω to 55Ω. The skew of propagation time of these signals should be minimized and the PCB trace length difference kept within ±50 mil. The following figure shows two commonly used PCB transmission line topologies. PCB Trace Ground Plane Microstrip Stripline Dielectric Figure 7: Trace Width Example The e MMC signals' trace length should be as short as possible; it is best kept to less than 2000 mil. The transmission line should be designed so that the conductor is as close to the ground plane as possible. This technique will couple the transmission line tightly to the ground plane and help decouple it from adjacent signals. It's best to widen spacing between signal lines as much as routing restrictions will allow, trying not to bring traces closer than three times the trace width. W Arc-shaped traces should be used instead of right-angle bends. Figure 8: Trace Shape Not recommended Recommended Recommended There should be NO breaks or voids in the ground plane under or over the high speed signals. 7

8 PCB Topology and Layout Figure 9: Avoiding Breaks and Voids Return current Return current Slot in image plane Slot in image plane Unacceptable Acceptable The best signaling is obtained when a constant reference plane is maintained. If a reference plane transition cannot be avoided, we recommend using the following techniques. If the signal reference plane changes from ground plane to power plane, adding capacitors near the via transition site will help support a good return path. If the signal reference plane changes from ground plane to another ground plane, ground vias should surround all high-speed signals (two ground vias per clock via; one ground via per high speed signal via). 8

9 PCB Topology and Layout Figure 10: Additional Capacitor for Return Current MLCC Trace Ground plane Power plane Figure 11: Typical Stub Case Trace Stubs should be kept short to avoid reflections. Stub propagation delay should be kept to <20% of the rise time of the signal. Branch 9

10 Revision History Revision History Rev. C 06/18 Rev. B 01/15 Rev. A 08/14 Added Capacitor Placement and Signal PCB Layout 100-Ball figure Updated the Host to Micron e MMC 5.0 Connection figure Initial release 8000 S. Federal Way, P.O. Box 6, Boise, ID , Tel: Sales inquiries: Micron and the Micron logo are trademarks of Micron Technology, Inc. All other trademarks are the property of their respective owners. 10