Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Like this presentation? Why not share!

- User Interface Functional Test Schemes by Epec Engineered T... 603 views
- Reliability of Copper PTH for High ... by Epec Engineered T... 1318 views
- How Many Cycles Can I Expect from M... by Epec Engineered T... 897 views
- Best PCB Layout Practices for Succe... by Epec Engineered T... 1747 views
- pcb layers in layout by Anum Mairaj 7381 views
- PCB by shweta16797 5139 views

1,495 views

Published on

This training module introduces the effect of PCB layout for high speed performance

Published in:
Technology

No Downloads

Total views

1,495

On SlideShare

0

From Embeds

0

Number of Embeds

3

Shares

0

Downloads

0

Comments

0

Likes

1

No embeds

No notes for slide

- 1. High Speed Amplifiers Part 2 <ul><li>Source: Analog Devices </li></ul>
- 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>This training module introduces the effect of PCB layout for high speed performance. </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Power Supply Bypassing </li></ul></ul><ul><ul><li>Parasitics </li></ul></ul><ul><ul><li>Ground and Power Planes </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>42 pages </li></ul></ul>
- 3. Power Supply Bypassing <ul><li>Bypassing is essential to high speed circuit performance </li></ul><ul><li>Capacitors right at power supply pins </li></ul><ul><ul><li>Capacitors provide low AC impedance to ground </li></ul></ul><ul><ul><li>Provide local charge storage for fast rising/falling edges </li></ul></ul>
- 4. Power Supply Bypassing <ul><li>Keep trace lengths short </li></ul>EQUIVALENT DECOUPLED POWER LINE CIRCUIT RESONATES AT: f = 1 2 LC IC +V S C1 L1 0.1 µF 1 µH f = 500kHz
- 5. Power Supply Bypassing <ul><li>Close to load return </li></ul><ul><ul><li>Helps minimize transient currents in the ground plane </li></ul></ul>
- 6. Power Supply Bypassing <ul><li>Values </li></ul><ul><ul><li>Individual circuit performance </li></ul></ul><ul><ul><li>Maintains low AC impedance </li></ul></ul><ul><li>Ferrite beads </li></ul>
- 7. Parasitics <ul><li>Parasite – An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of its host. </li></ul><ul><li>Parasitics in high-speed PCB’s, can degrade or destroy circuit performance! </li></ul>
- 8. Parasitics <ul><li>PCB parasites take the form of undesired capacitors, inductors and resistors embedded within the PCB </li></ul><ul><li>Parasitics are extremely difficult to remove from a PCB </li></ul><ul><li>Prevention is the best method to minimize parasitics </li></ul>
- 9. Trace/Pad Capacitance d A K = relative dielectric constant A = area in cm 2 d = spacing between plates in cm
- 10. Trace/Pad Capacitance d A K = relative dielectric constant A = area in cm 2 d = spacing between plates in cm Example: Pad of SOIC L = 0.2cm W = 0.063cm K= 4.7 A = 0.0126cm 2 d = 0.073cm C = 0.072pF
- 11. Trace/Pad Capacitance d A K = relative dielectric constant A = area in cm 2 d = spacing between plates in cm Example: Pad of SOIC L = 0.2cm W = 0.063cm K= 4.7 A = 0.0126cm 2 d = 0.073cm C = 0.072pF Reduce Capacitance 1) Increase board thickness or layers 2) Reduce trace/pad area 3) Remove ground plane
- 12. Approximate Trace Inductance All dimensions are in mm
- 13. Approximate Trace Inductance Example L= 25.4mm W = .25mm H = .035mm (1oz copper) Strip Inductance = 28.8nH At 10MHz Z L = 1.86 a 3.6% error in a 50 system All dimensions are in mm
- 14. Approximate Trace Inductance Example L= 2.54cm =25.4mm W = .25mm H = .035mm (1oz copper) Strip Inductance = 28.8nH At 10MHz Z L = 1.86 a 3.6% error in a 50 system All dimensions are in mm Minimize Inductance 1) Use Ground plane 2) Keep length short (halving the length reduces inductance by 44%) 3) Doubling width only reduces inductance by 11%
- 15. Via Parasitics L = inductance of the via, nH H = length of via, cm D = diameter of via, cm Given: H= 0.157 cm thick board, D= 0.041 cm Via Inductance Via Capacitance L ~ 1.2nh D 2 = diameter of clearance hole in the ground plane, cm D 1 = diameter of pad surrounding via, cm T = thickness of printed circuit board, cm = relative electric permeability of circuit board material C = parasitic via capacitance, pF Given: T = 0.157cm, D 1 =0.071cm D 2 = 0.127 nH C ~ 0.51pf pF
- 16. Via Cross Section T&H D D 2 D 1
- 17. Capacitor Parasitic Model C = Capacitor R P = insulation resistance R S = equivalent series resistance (ESR) L = series inductance of the leads and plates R DA = dielectric absorption C DA = dielectric absorption
- 18. Resistor Parasitic Model R = Resistor C P = Parallel capacitance L= equivalent series inductance (ESL)
- 19. Low Frequency Op Amp Schematic
- 20. High Speed Op Amp Schematic
- 21. High Speed Op Amp Schematic Parasitic Capacitance
- 22. Stray Capacitance Simulation Schematic
- 23. Frequency Response with 2pF Stray Capacitance 1.8dB peaking 1.8dB peaking
- 24. Stray Inductance Parasitic Inductance
- 25. Parasitic Inductance Simulation Schematic AD8055 24.5mm x .25mm” =29nH
- 26. Pulse Response With and Without Ground Plane 0.6dB overshoot
- 27. Transient Response AD8009 1GHz Current Feedback Amplifier R F 150Ω 402 Ω 402 Ω R G -5V +5V 10uF 0.1uF 0.1uF 10uF
- 28. Small Changes Can Make a Big Difference! Circuit B Circuit A
- 29. Improper Use of Scope Probe Ground Clip
- 30. Effect of Clip Lead Inductance
- 31. Proper Grounding for Scope Probe in High-Speed Measurments
- 32. Small Changes Make Big Differences Circuit B Circuit A 21ns 17ns 25% reduction in ringing duration and amplitude
- 33. Ground and Power Planes Provide <ul><li>A common reference point </li></ul><ul><li>Shielding </li></ul><ul><li>Lower noise </li></ul><ul><li>Lower resistance </li></ul><ul><li>Lower impedance </li></ul><ul><li>Reduces parasitics </li></ul><ul><li>Heat sink </li></ul><ul><li>Power distribution </li></ul>
- 34. Ground Plane Conductor I I Dielectric Ground Plane
- 35. Sensitive Analog Circuitry Disrupted by Digital Supply Noise Ground Plane and Trace Routing Wrong Way ANALOG CIRCUITS DIGITAL CIRCUITS V D V A + + I D I A I D I A + I D V IN GND REF INCORRECT Input Connector
- 36. Sensitive Analog Circuitry Disrupted by Digital Supply Noise Ground Plane and Trace Routing Wrong Way ANALOG CIRCUITS DIGITAL CIRCUITS V D V A + + I D I A I D I A + I D V IN GND REF INCORRECT
- 37. Sensitive Analog Circuitry Safe from Digital Supply Noise Ground Plane and Trace Routing Right Way ANALOG CIRCUITS DIGITAL CIRCUITS V D V A + + V IN I D I A I D I A GND REF CORRECT
- 38. <ul><li>Grounding Example: </li></ul><ul><ul><li>Top layer is solid ground. </li></ul></ul><ul><ul><li>Bottom has a trace/transmission line connecting the RF connector to the load. </li></ul></ul><ul><ul><li>Return current flows in the top layer ground plane directly above the trace on the opposite side. </li></ul></ul>Top Side Bottom side Ground Plane and Trace Routing Signal Input Termination Resistor
- 39. <ul><li>Grounding Example: DC Current vs. AC Current: </li></ul><ul><ul><li>In a split or broken ground, the return currents follow the path of least impedance </li></ul></ul><ul><ul><li>At DC, the current follows the path of least resistance </li></ul></ul><ul><ul><li>As the frequency increases, the current follows the path of least inductance </li></ul></ul><ul><ul><li>Since there is now a ‘loop’ the inductance can be quite high and the circuit can now propagate EMI/RFI </li></ul></ul>Ground Plane and Trace Routing DC current follows the path of least resistance AC current follows the path of least impedance
- 40. Grounding Mixed Signal ICs: Single PC Board ANALOG CIRCUITS DIGITAL CIRCUITS A A D D D V A V D ANALOG GROUND PLANE DIGITAL GROUND PLANE AGND DGND MIXED SIGNAL DEVICE A DIGITAL SUPPLY ANALOG SUPPLY SYSTEM STAR GROUND V A V D
- 41. Ground Plane Recommendations <ul><li>There is no single grounding method which is guaranteed to work 100% of the time! </li></ul><ul><li>Remove ground plane under op amps to reduce parasitic capacitance </li></ul><ul><li>At least one layer on each PC board MUST be dedicated to ground plane! </li></ul><ul><li>Provide as much ground plane as possible especially under traces that operate at high frequency </li></ul><ul><li>Use thickest metal as feasible (reduces resistance and provides improved thermal transfer) </li></ul><ul><li>Use multiple vias to connect same ground planes together </li></ul><ul><li>Do initial layout with split analog and digital ground planes </li></ul><ul><li>Follow recommendations on device data sheet (read datasheet) </li></ul><ul><li>Keep bypass capacitors and load returns close to reduce distortion </li></ul><ul><li>Connect analog, digital and RF grounds at one point </li></ul>
- 42. Additional Resource <ul><li>For ordering high speed operational amplifiers, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For additional inquires contact our technical service hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/products/index.html </li></ul></ul>Newark Farnell

No public clipboards found for this slide

×
### Save the most important slides with Clipping

Clipping is a handy way to collect and organize the most important slides from a presentation. You can keep your great finds in clipboards organized around topics.

Be the first to comment