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- 5. Confidential and Proprietary– Qualcomm Technologies, Inc. Restricted Distribution: Not to be distributed to anyone who is not an employee of either Qualcomm or its subsidiaries without the express approval of Qualcomm’s Configuration Management. 80-VT310-13 Rev. F Power Delivery Network Design Training
- 6. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 2 Confidential and Proprietary – Qualcomm Technologies, Inc. NO PUBLIC DISCLOSURE PERMITTED: Please report postings of this document on public servers or websites to: DocCtrlAgent@qualcomm.com. Restricted Distribution: Not to be distributed to anyone who is not an employee of either Qualcomm or its subsidiaries without the express approval of Qualcomm’s Configuration Management. Not to be used, copied, reproduced, or modified in whole or in part, nor its contents revealed in any manner to others without the express written permission of Qualcomm Technologies, Inc. Qualcomm is a trademark of QUALCOMM Incorporated, registered in the United States and other countries. MSM is a trademark of QUALCOMM Incorporated, registered in the United States and other countries. All QUALCOMM Incorporated trademarks are used with permission. Other product and brand names may be trademarks or registered trademarks of their respective owners. This technical data may be subject to U.S. and international export, re-export, or transfer (“export”) laws. Diversion contrary to U.S. and international law is strictly prohibited. Qualcomm Technologies, Inc. 5775 Morehouse Drive San Diego, CA 92121 U.S.A. © 2010, 2012, 2014 Qualcomm Technologies, Inc.
- 7. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 3 Revision Date Description A June 2010 Initial release B July 2010 Introduction: Enhanced definition of Vmin and Vmax. Explained that, beyond 25 MHz, the PDN is dominated by device package internal RLC circuits. PDN Theory: Added this section. PCB Design Requirements: For frequency range 300 kHz–10 MHz, added the comment that each decoupling cap must have its own via directly to the ground plane. PDN Design Example: Clarified the reference design example as using the QSD8650A™ device. Added an important note about the need for PMIC bulk caps. Clarified the case 5 plots and added an explanation related to the increase/decrease of C/L. FAQ: Rewritten, adding new FAQs. Added more information on simulation. C August 2010 Clarified the following FAQs: FAQ – PDN Guidelines; added figures and replaced the “fr” acronym with “ac” FAQ – PDN Measurement Recommendations; added a figure FAQ – Stress Test for Other Power Rails; reworded sentences Added the following new FAQs: FAQ – Mentor Graphics PADS Files FAQ – Precautions for Layout Files FAQ – PCB Stack-up FAQ – Measuring PMIC DC Error D September 2010 •Slide 6 – Added new slide, Scope and Intended Audience •Slide 8 – Corrected typo in V(t) formula for F-1 in the Introduction •Slide 14 – PDN Theory – updated figure for clarification •Slide 18 – PCB Z(w) Design Guidelines – Removed the recommendation for 2x voltage rating on capacitor selection •Slide 22: •Added for PCB to PDN Maximum Impedance Guideline title •Added new device MSM7x27T to PDN Maximum Impedance Guidelines •Slide 25 – PDN Design Example – Added a note that all plots are simulations and correlate with actual measured data Revision History (1 of 4)
- 8. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 4 Revision Date Description D (cont.) September 2010 •Slide 26 – PDN Design Example – Added a note about 10 mohm target PDN impedance guideline for DC •Slide 39 – PDN Design Example, Modification 5, Step 3 – Labeled GND and power layers •FAQ section: •Slide 45 – FAQ – PDN Design Guidelines – Changed terminology Vpm to Vpmdcerror for consistency with other slide and added scale in figure. •Slide 50 – Files Needed for Simulation – Added a note about providing PCB stack-up information •Slides 53 and 54 – Preparation for Layout File – Added examples •Slide 63 – Distance and Heat Concentration – Added note about thermal conductivity •Slides 67 and 68 – Via Routing – Updated figure for clarification •Slide 75 – Measuring PMIC DC Error – Corrected formula in Vmargin_h, and removed rework for new configuration requirement •Added the following new FAQ: •Slide 55 – Turn Around Time for Simulations •Slides 56 and 57 – Flow Chart of the Simulation Environment •Slide 78 – Overshoot Impact •Slide 79 – Zero Ohm Resistor E April 2012 •Slide 6 – Added AC1 and FAQ sub-sections to Agenda •Slide 7 – Added Terms and Definitions •Slide 17 – PDN Theory – Modified PDN circuit diagram •Slide 25 – PDN Theory– Added Static IR Drop •Slide 26 – PDN Theory – Added PCB Stack-up Considerations •Slide 27 – PDN Theory – Added Capacitor Placements •Slide 28 – PDN Theory – Added Decoupling Capacitor Routing Scenarios •Slide 50 – AC1 Stress Test – Added title slide •Slide 51 – AC1 Stress Test – Added Introduction and Recommended lab setup information •Slide 52 – AC1 Stress Test – Added Probe Setup •Slide 53 – AC1 Stress Test – Added Typical AC1 Waveform •Slide 54 – AC1 Stress Test – Added Terms and Definitions •Slide 55 – AC1 Stress Test – Added Terms and Definitions (cont.) •Slide 56 – AC1 Stress Test – Added Margin Calculations •Slide 57 – FAQ General – Added title slide •Slide 58 – FAQ General – Added PDN Targets Revision History (2 of 4)
- 9. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 5 Revision Date Description E (cont.) April 2012 •Slide 60 – FAQ General – Modified PDN Guidelines (cont.) •Slide 62 – FAQ General – Modified VRM Models, Transient Simulations •Slide 73 – FAQ Simulation – Added new title •Slide 77 – FAQ Simulation – Added additional files to be provided from Rev B. •Slide 86 – FAQ Simulation – Added PMIC Models •Slide 87 – FAQ Simulation – Added Package/Die Models •Slide 88 – FAQ Simulation – Added Port Definition •Slide 89 – FAQ Simulation – Added Resistance Measurement •Slide 90 – FAQ Simulation – Added Current Measuring Resistor •Slide 91 – FAQ Simulation – Added Time Domain Simulation •Slide 92 – FAQ Simulation – Added Chip Power Model •Slide 93 – FAQ Simulation – Added Transient Simulation •Slide 94 – FAQ AC1 Stress Test – Added new title •Slide 95 – FAQ AC1 Stress Test – Added Stress Tests for Other Power Rails •Slide 96 – FAQ Impedance Measurement – Added new title •Slide 97 – FAQ Impedance Measurement – Added Simulation vs. Lab Measurement Correlation F October 2014 • Clarified throughout the document that PDN simulations must be done as soon as parts placement and PDN routing is finished. Also changed “targets” to “specifications” throughout the document • Clarified throughout the document that the regulator in the PDN system can be SMPS or LDO • Removed obsolete references to QSD from the document • Slide 8 – Terms and Definitions: Modified the definition of bulk capacitors and local decoupling capacitors • Slide 11 – Introduction: Clarified the introduction • Slide 19 – Key Concept – Loop Inductance: Added a slide to explain loop inductance and identify the key items for reducing it • Slide 23-26 – PCB Z(ω) Design Guidelines: Modified the explanations on the graphs • Slide 53 – Stress Test: Clarified the use of AC1 and added that customers should also run their own high concurrency tests at temperature extremes • Slide 55 – Stress Test Probe Setup: Added arrows indicating where to solder the shield and center conductor of the semi-rigid coaxial shield • Slides 66 – General – PDN Specifications: Modified answers for frequently answered questions • Slides 67-68 – General – Failure to Meet PDN Specifications: Added slides to frequently answered questions Revision History (3 of 4)
- 10. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 6 Revision Date Description F (cont.) October 2014 •Slide 73 – General – Via Routing: Modified the figure to show both power and ground routing. •Slide 74 – General – PCB Area and BOM Count: Modified the answers •Slide 75 – General – Placement Distance between PMIC and the Processor: Clarified that thermal considerations take priority when determining the distance from the PMIC to the MSM •Slide 81 – General – Simulation Tools: Modified the answers •Slide 89 – General – Flowchart of Simulation Procedures: Modified the flowchart and deleted the second page •Slide 90 – General – PMIC Models: Modified the answer about the PMIC VRM model •Slide 92 – General – Port Definition: Modified the answer to include distributed ports Revision History (3 of 4)
- 11. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 7 Contents 1 Introduction 9 2 PDN Theory 13 2.1 PCB Z(ω) Design Guidelines 22 3 PDN Design Example – Simulation 32 4 Stress Test (AC1) 52 5 Frequently Asked Questions 62 5.1 General 63 5.2 Simulation 79
- 12. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 8 Terms and Definitions Term Definition Processor Qualcomm Technologies, Inc. (QTI) ICs – MSM™, APQ, MPQ, and MDM Bulk capacitors Capacitors to smooth PMIC output response, normally by ≥ 4.7 µF Local decoupling capacitors Capacitors closest to the processor. These capacitors improve processor response to transient current demand, normally by ≤ 1 µF
- 13. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 9 Introduction Section 1
- 14. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 10 This document is intended for engineers who are designing with QTI devices that operate with clock frequencies of approximately 800 MHz and higher. This document contains important information about how to design the power delivery network (PDN) to minimize impedance over the frequency range of interest. Proper PDN design prevents violations of Vmin or Vmax during voltage transients that occur under normal operating conditions. What is included in the PDN? Voltage regulators residing in the power management IC (PMIC) Switched mode power supply (SMPS) Low-dropout regulator (LDO) Regulator output inductor (SMPS only) + bulk capacitor(s) All passive components and their connections to the processor power grid Copper traces connecting the regulator output to the processor power pins Copper plane connecting processor ground pins to regulator ground pins Scope and Intended Audience Sec. 1
- 15. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 11 A properly designed PDN helps ensure supply voltage compliance to the required operating conditions of processors and other integrated circuitry. Proper PDN design ensures that Vmin ≤ V(t) ≤ Vmax during all di/dt events. V(t) is the voltage measured at the processor power pins as a function of time. Vmin is the minimum voltage allowed (DC + transient) at the processor power supply pins to guarantee proper operation over all variations of process and temperature as listed in the device specification. Vmax is the maximum voltage allowed (DC + transient) at the processor power supply pins to guarantee proper operation over all variations of process and temperature as listed in the device specification. Introduction (1 of 2) Sec. 1
- 16. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 12 Key formula: V(t) = VDD(t) ± F-1{Z(ω)I(ω)} VDD (t) is the instantaneous voltage at the PMIC output. I(w) is the load current as a function of frequency. Z(w) is the impedance of the PDN determined from the load (processor power supply pins), back toward the PMIC and is dominated by: – PCB metal power planes (DC to ~3 kHz) – PMIC regulator response and external bulk capacitors (~3 kHz to ~300 kHz) – PCB metal planes and local decoupling capacitor values (~300 kHz to ~10 MHz) – Local decoupling capacitor connections to processor power supply pins and distance between power and ground planes (~10 MHz onwards) Introduction (2 of 2) Sec. 1
- 17. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 13 PDN Theory Section 2 2.1 PCB Z(ω) Design Guidelines 22
- 18. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 14 Impedance: Resistor Z = R Inductor Z = jωL Capacitor Z = 1/(jωC) On a log/log scale, these impedances graph as lines of constant slope vs ω. Z(f): R, L, C R = 1 Ω C = 1 nF L = 1 nH Increasing C Increasing L Resonance frequency Sec. 2
- 19. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 15 Series RLC Resonance LC f π 2 1 0 = R C L |Z|, Ohm Sec. 2
- 20. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 16 Parallel RLC Resonance LC f π 2 1 0 = |Z|, Ohm R L C Sec. 2
- 21. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 17 The PDN impedance (Z) is modeled by combinations of capacitance, inductance, and resistance. Inductor: Z = jωL Capacitor: Z = 1/(jωC) Resistor: Z = R Combinations of larger inductance and smaller capacitance result in a higher impedance. Combinations of smaller inductance and larger capacitance result in a lower impedance. PDN Theory (1 of 5) Sec. 2
- 22. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 18 PDN Theory (2 of 5) Note: This is a simplified PDN model. Sec. 2
- 23. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 19 The amount of loop inductance associated with the PDN routing on a PCB is primarily determined by: The physical dimensions of the current carrying conductors (power net) and the closeness of the return path (ground net). The physical dimensions and placement of the passive components connected to the PDN (primarily decoupling capacitors and possibly resistors). Loop inductance is directly proportional to the area encompassed by a power net and its return path. A large area implies a large loop inductance. Therefore, key steps to reducing loop inductance are: Reducing the lengths (x) of both power and ground nets. Reducing the vertical distance (y) between power and ground (return) nets. See the Stack-up Considerations slide. Routing multiple current loops in parallel. Ltotal = L1 × L2/(L1 + L2). This is because the parallel loops can support more current for the same voltage drop. Wider power and ground (return) traces with broadside (over-under) coupling effectively provide more loops in parallel to reduce inductance. Optimally placing and connecting decoupling capacitors. This reduces effective loop area because the capacitors electrically close the parallel inductive branch loops; good placement + connection = smaller loops in parallel. See the Capacitor Placements slide. Key Concept – Loop Inductance PDN Theory (3 of 5) Sec. 2
- 24. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 20 At higher frequencies (not shown in figure), the PDN impedance is a function of package RLC and board loop inductance. PDN Theory (4 of 5) Note: The exact frequencies Fa, Fb, and Fc depend on the PMIC regulator used, bulk capacitors, inductor (SMPS only), board impedance, decoupling capacitors, etc. PCB PMIC + Bulk capacitors PCB + Decoupling capacitors Connections to local decoupling capacitors, their placement relative to the power pins, and their values 0 Fa ~ 3 kHz Fb ~ 300 kHz Fc ~ 10 MHz Impedance, Z (Ohm) Sec. 2
- 25. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 21 The PDN response in a given frequency range can be resistive, capacitive, or inductive. It is composed of both series and parallel resonances as shown below. PDN Theory (5 of 5) Inductive Capacitive 10 MHz Resistive Impedance Z Capacitive Inductive (Overall PCB Loop Inductance) Inductive 25 MHz 100 kHz Power Supply Response Sec. 2
- 26. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 22 PCB Z(ω) Design Guidelines Section 2.1
- 27. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 23 PCB PMIC + Bulk capacitors PCB + Decoupling capacitors Connections to local decoupling capacitors, their placement relative to the power pins, and their values 0 Fa ~ 3 kHz Impedance, Z (Ohm) Fb ~ 300 kHz Fc ~ 10 MHz DC–3 kHz → PCB metal routing to meet the DC resistance specification First, address thermal design requirements relative to the placement of the PMIC and processor Maximize metal thickness (½ vs. ⅓ oz. Cu) Use sufficiently wide power traces Use multiple parallel power and ground vias PCB Z(ω) Design Guidelines (1 of 4) Sec. 2.1
- 28. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 24 PCB PMIC + Bulk capacitors PCB + Decoupling capacitors Connections to local decoupling capacitors, their placement relative to the power pins, and their values 0 Fa ~ 3 kHz Impedance, Z (Ohm) Fb ~ 300 kHz Fc ~ 10 MHz 3 kHz–300 kHz → PMIC regulator response and bulk capacitors Use QTI-supplied PMIC settings and reference schematic values Follow QTI design guidelines for optimal placement of the bulk capacitors Maximize metal thickness (½ vs. ⅓ oz. Cu); use wider power traces Use multiple parallel power and ground vias PCB Z(ω) Design Guidelines (2 of 4) Sec. 2.1
- 29. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 25 PCB PMIC + Bulk capacitors PCB + Decoupling capacitors Connections to local decoupling capacitors, their placement relative to the power pins, and their values 0 Fa ~ 3 kHz Impedance, Z (Ohm) Fb ~ 300 kHz Fc ~ 10 MHz 300 kHz–10 MHz → PCB layout and decoupling capacitors Engineer capacitor values, body sizes, and placement to meet impedance specification PCB Z(ω) Design Guidelines (3 of 4) Sec. 2.1
- 30. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 26 PCB PMIC + Bulk capacitors PCB + Decoupling capacitors Connections to local decoupling capacitors, their placement relative to the power pins, and their values 0 Fa ~ 3 kHz Impedance, Z (Ohm) Fb ~ 300 kHz Fc ~ 10 MHz 10 MHz onwards → Capacitors and PCB connection Current always takes the path of least impedance. At these high frequencies, PDN loop inductance, value, and placement of capacitors attached to power pins dominates impedance. Local decoupling capacitors should be placed as close as possible to the processor power and ground pins. Use back-side capacitors if possible. Each capacitor should have its own via directly to the ground plane and power plane layer. Power and ground vias and planes should be as close together as possible. See the Stack-up Considerations and Capacitor Placements slides. PCB Z(ω) Design Guidelines (4 of 4) Sec. 2.1
- 31. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 27 Calculate the resistance of power trace between PMIC and MSM using: R = ρ (L/A) where ρ = Resistivity of copper L = Length of trace A = Cross-section area = Width of trace × thickness of trace Calculate the minimum number of vias required to carry the current. Always use more vias than the minimum required. Minimum vias ≥ Total current/Current carrying capacity of each via Copper paste filled vias are used in certain PCBs. Copper paste is electrically and thermally less conductive than copper. More vias are required when using copper paste vias. Static IR drop analysis shows current densities at different locations in the layout. PCB Z(ω) Design Guidelines – Static DC IR Drop Sec. 2.1
- 32. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 28 Power and ground should be located on adjacent layers separated by as thin a dielectric as possible to reduce loop inductance. PCB Z(ω) Design Guidelines – Stack-up Considerations No Layer Thickness (μm) Scenario I Scenario II 1 Cu 25 Dielectric 50 2 Cu 20 Dielectric 50 3 Cu 20 Gnd Signal Dielectric 65 4 Cu 20 Signal Gnd Dielectric 65 5 Cu 17 Pwr Pwr CORE 100 6 Cu 17 Gnd Signal Dielectric 65 7 Cu 20 Signal Gnd Dielectric 65 8 Cu 20 Dielectric 50 9 Cu 20 Dielectric 50 10 Cu 25 Better (Dielectric is thinner) Worse (Dielectric is thicker) Sec. 2.1
- 33. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 29 Lower power-ground loop area reduces loop inductance thereby improving the effectiveness of a capacitor at high frequencies. Local decoupling capacitors must be placed as close to the MSM pins as possible. PCB Z(ω) Design Guidelines – Capacitor Placements Note: Geometries are not to scale. Sec. 2.1
- 34. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 30 Capacitor effective loop inductance is geometry based. Body size influences self-inductance; capacitors with smaller body sizes have lower ESL. Locate power-ground vias as close to each other as possible; small loops have lower inductance. Locate vias close to the capacitor terminals; small loops have lower inductance. Multiple parallel power-ground via pair connections reduce mounting inductance; parallel loops have lower inductance. Avoid sharing vias with adjacent capacitors; parallel loops have lower inductance, series loops have higher inductance. Three-terminal capacitors such as X2Y devices can offer lower inductance than two-terminal devices. With good layout the three-terminal devices are connected with small loops and parallel loops. The multiple terminal design also provides small loops and parallel loops inside the device for lower ESL. PCB Z(ω) Design Guidelines – Decoupling Capacitor Routing Sec. 2.1
- 35. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 31 PCB Z(ω) Design Guidelines – Decoupling Capacitors Response and Routing Decreasing inductance 2-T Capacitors 3-T X2Y Capacitors Good Bad Avoid sharing vias Good Layout Poor Layout Poor Layout Good Layout Typical Capacitor Response Sec. 2.1
- 36. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 32 PDN Design Example – Simulation Section 3 Steps to Reduce the PDN Impedance of the PCB
- 37. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 33 The following definitions are used throughout this design example: Effective capacitance: The total shunt capacitance over the PDN between the source and the load Effective inductance: The loop inductance from the processor power pins to the closest “local” bypass capacitors PDN Design Example (1 of 2) Sec. 3
- 38. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 34 This PDN impedance reduction example uses the QSD8650A device. Note: All impedance graphs shown in the following slides are simulated results that correlate accurately to measured results. Bulk capacitor (at the PMIC output) (modification case 1) Wide traces/copper fill (modification case 2 and case 3) Local decoupling capacitors (at the MSM input) Placement (minimize the distance to the processor power supply pins) (modification case 4, step 1 and case 5, step 1) Value (modification case 5, step 2) Layer thickness (modification case 5, step 3) Distance between PMIC and the processor power supply pins (General – Via Routing ) Distance between power and ground planes (General – PCB Area and BOM Count) Via (General – Trace Width) PDN Design Example (2 of 2) Sec. 3
- 39. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 35 DC resistance (by PowerDC): Power path: From MSM/QSD to R504: 1 mΩ R504: 4 mΩ From R504 to L402: 6.5 mΩ (11.5 mΩ total) Ground path: From U201 to GND node near L402: 1.7 mΩ Total is 11.5 mΩ + 1.7 mΩ = 13.2 mΩ – This does not meet the 10 mΩ specification at DC. Original Layout/Conditions Capacitance 2.2 µF 1 µF 22 µF Quantity 9 4 1 Port 1 – Processor Port 2 – PMIC (L402) Sec. 3
- 40. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 36 Modification – Case 1 Capacitance Original Case 1 2.2 µF 9 9 1 µF 4 4 22 µF 1 1 47 µF – 2 Total 14 16 Add more bulk capacitors at the PMIC side to improve the low-frequency response. Sec. 3
- 41. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 37 Change in PDN Impedance – Case 1 Effective C Effective L Original 45.3 µF 1.05 nH New 137.2 µF 1.05 nH Observation: Large bulk capacitors improve PDN impedance as shown, but even more important is their role in reducing PMIC effective impedance below 100 kHz (not shown in these simulations). Follow the PMIC data sheet and reference schematic for proper values (i.e., the QSD8250A PMIC only recommends a 22 µF maximum bulk capacitor). PMIC = ideal voltage source 1E5 1E6 1E7 1E4 1E8 1E-2 1E-1 1E-3 1 freq, Hz Original New Z specification Z is decreased due to 47 µF capacitors Effective L unchanged Sec. 3
- 42. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 38 Replace the 2.2 µF capacitors with 4.7 µF with no change to routing. No layout/capacitor placement changes Replaced only the 2.2 µF capacitor with 4.7 µF capacitors and replaced the 1 µF capacitors with 0.47 µF capacitors Modification – Case 2 Capacitance Original New 2.2 µF 9 – 1 µF 4 – 4.7 µF – 9 0.47 µF – 4 22 µF 1 1 47 µF – – Total 14 14 Sec. 3
- 43. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 39 Change in PDN Impedance – Case 2 Effective C Effective L Original 45.3 µF 1.05 nH New 66.3 µF 1.05 nH Observation: Increasing the value of local capacitors without changing the PDN routing did not help reduce the effective inductance. Effective inductance is dominated by the current path from the chip pins to the local decoupling capacitors, not the capacitor values themselves. PMIC = ideal voltage source 1E5 1E6 1E7 1E4 1E8 1E-2 1E-1 1E-3 1 freq, Hz Original New Z specification Effective L unchanged Z is lowered due to 9 × 2.2 µF capacitors changing to 9 × 4.7 µF Z is slightly increased due to 4 × 1 µF changing to 4 × 0.47 µF Sec. 3
- 44. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 40 Modification – Case 3 Capacitance Original New 2.2 µF 9 9 1 µF 4 4 22 µF 1 1 Total 14 14 Take out the current measurement resistor and fill in the shape. No changes in the bypass capacitor arrangements Sec. 3
- 45. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 41 Change in PDN Impedance – Case 3 Effective C Effective L Original 45.3 µF 1.05 nH New 45.3 µF 1.05 nH PMIC = ideal voltage source Observation: Removing the series R showed a 4 mΩ improvement in low-frequency impedance from the MSM chip to the PMIC (see Original Layout/Conditions). 1E5 1E6 1E7 1E4 1E8 1E-2 1E-1 1E-3 1 freq, Hz Original New Z specification Small decrease in Z due to removal of series resistance in the routing. Sec. 3
- 46. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 42 Modification – Case 4 Capacitance Original New 2.2 µF 9 13 1 µF 4 4 22 µF 1 1 Total 14 18 Add four back-side bypass capacitors. Top and bottom layer Bottom layer only Four extra 2.2 µF capacitors were added on the opposite side from the chip. Sec. 3
- 47. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 43 Change in PDN Impedance – Case 4 Effective C Effective L Original 45.3 µF 1.05 nH New 54.7 µF 0.83 nH Observation: Adding back-side capacitors without optimizing the capacitor routing only marginally reduced the PDN inductance. The next case shows that re-engineering the routing of those capacitors was key. PMIC = ideal voltage source 1E5 1E6 1E7 1E4 1E8 1E-2 1E-1 1E-3 1 freq, Hz Original New Z specification Use of backside capacitors without effective routing caused only a small reduction in effective L. Backside capacitor loop balances series and parallel resonances to flatten response. Sec. 3
- 48. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 44 Use back-side capacitors and reduce the size of other capacitors to place them as close to the processor power pins as possible. Modification – Case 5 Step 1 Capacitance Original New 0.47 µF (same side) – 7 0.47 µF (back side) – 7 2.2 µF 9 – 1 µF 4 – 22 µF 1 1 Total 14 15 Power routing (all layer view) Local decoupling capacitor placement (top/bottom layers) Reduced overall DC resistance from U14 (MSM) to PMIC by decreasing length and widening the PDN trace Power: 6.3 mΩ; GND: 3.5 mΩ Total loop: 9.8 mΩ vs. 13.2 mΩ original (26% reduction) Sec. 3
- 49. Confidential and Proprietary– Qualcomm Technologies, Inc. | MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION | 80-VT310-13 Rev. F 45 Change in PDN Impedance – Case 5 Step 1 Effective C Effective L Original 45.3 µF 1.05 nH Step 1 29.0 µF 0.17 nH PMIC = ideal voltage source Observation: With an improved breakout strategy and re-engineering of the via patterns, the PDN impedance is significantly reduced at both low and high frequency. Back-side capacitors with close placement and short routing of the traces to the processor power pins and ground plane reduce effective L. However, reduction of effective C has caused an increase in impedance at mid frequency. 1E5 1E6 1E7 1E4 1E8 1E-2 1E-1 1E-3 1 freq, Hz Original New Z specification Properly routed backside capacitors enable significant decrease of effective L. Z increases due to reduction of effective C. PMIC to MSM PDN shorter and wider Sec. 3
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- 70. 〈大力將軍〉 查伊璜，浙人，清明飲野寺中，見殿前有古鍾，大於兩石甕， 而上下土痕手蹟，滑然如新。疑之。俯窺其下，有竹筐受八升許，不 知所貯何物。使數人摳耳，力掀擧之無少動，益駭。乃坐飲以伺其 人；居無何，有乞兒入，擕所得糗糒，堆累鍾下。乃以一手起鍾，一 手掬餌置筐内，往返數回始盡。已複合之乃去，移時複來，探取食 之。食已複探，輕若啟櫝。一座盡駭。查問：“若個男兒胡行乞？”答 以：“啖噉多，無傭者。”查以其健，勸投行伍，乞人愀然慮無階。查 遂擕歸餌之，計其食，略倍五六人。爲易衣履，又以五十金贈之行。 後十餘年，查猶子令於閩，有吳將軍六一者，忽來通謁。款談 間 ， 問： “ 伊 璜 是 君 何 人 ？ ” 答 言 ： “ 爲 諸 父 行 。 與 將 軍 何 處 有 素？”曰：“是我師也。十年之别，頗複憶念。煩致先生一賜臨也。”漫 應之。自念叔名賢，何得武弟子？會伊璜至，因告之，伊璜茫不記 憶。因其問訊之殷，即命僕馬，投刺於門。將軍趨出，逆諸大門之 外。視之，殊昧生平。竊疑將軍誤，而將軍傴僂益恭。肅客入，深啟 三四關，忽見女子往來，知爲私廨，屏足立。將軍又揖之。少間登 堂，則卷簾者、移座者，並皆少姬。既坐，方擬展問，將軍頤少動， 一姬捧朝服至，將軍遽起更衣，查不知其何爲。眾嫗捉袖整衿訖，先 命數人撩查座上不使動，而後朝拜，如覲君父。查大愕，莫解所以。 拜已，以便服侍坐。笑曰：“先生不憶擧鍾之乞人耶？”查乃悟。既而 華筵高列，家樂作於下。酒闌，群姬列侍。將軍入室，請衽何趾，乃 去。 查醉起遲，將軍已於寢門三問矣。查不自安，辭欲返，將軍投 轄下鑰，錮閉之。見將軍日無别作，惟點數姬婢養廝卒，及騾馬服用 器具，督造記籍，戒無虧漏。查以將軍家政，故未深叩。一日，執籍 謂查曰：“不才得有今日，悉出高厚之喝。一婢一物，所不敢私，敢以 半奉先生。”查愕然不受，將軍不聽。出藏鏹數萬，亦兩置之。按籍點 照，古玩床幾，堂内外羅列幾滿。查固止之，將軍不顧。稽婢僕姓名
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