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RAD Engineering BLM VME J2 Backplane

RAD Engineering BLM VME J2 Backplane. Printed Circuit Board Backplane Crosstalk Comparison January 25, 2005. Initial Look at Crosstalk. How does the RAD Engineering design affect crosstalk and signal quality?

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RAD Engineering BLM VME J2 Backplane

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  1. RAD EngineeringBLM VME J2 Backplane Printed Circuit Board Backplane Crosstalk Comparison January 25, 2005

  2. Initial Look at Crosstalk • How does the RAD Engineering design affect crosstalk and signal quality? • Where to start? Al suggests comparing what we have (RAD Engineering) with another commercial backplane. • Fortunately? We have a Bicc-Vero VME J2 backplane lying around. • Not great, but something to start with.

  3. Test Equipment Used • Scope: HP 54825A Infinium Oscilloscope, 500 MHz, 2 Ga/s • Probes: HP 1160A Probes 500 MHz, 10 Meg Ohm, 9pf • Pattern Generator: HP 16520A 50 M/bit Second Data Rate • RAD Engineering VME J2 Backplane

  4. Basic Checks on Signal Lines • Backplane current draw with just built-in (B Row) terminations = 0.304 Amps. • Backplane current draw with built-in and Control Bus terminations = 1.151 Amps. • Measured termination voltages for Control Bus signal lines, D0-D7, pins 19-26. • Pin 19 D0 = 2.993V, Pin 20 D1 = 3.001V, Pin 21 D2 = 3.002V • Pin 23 D3 = 2.998V, Pin 24 D4 = 2.999V, Pin 25 D5 = 2.997V • Pin 26 D6 = 2.994V, Pin 27 D7 = 2.997V • VME spec. for termination voltage is: 2.94V, +/-10%

  5. Test Pulse Pattern • Backplane Vcc = 5.10V • Input Pulse Level High = 3.00V, Low = 0.20V • Output Pulse Level = TTL (74F241 Buffer) • Pulse Pattern has a 50ns or 100ns bit time. • Initial Pulse Pattern is binary count sequence. • Pulse Pattern then changes to all 1’s & 0’s. • Pattern Generator buffered output and signal of interest terminated properly at each end of the backplane (Standard VME Practice).

  6. Test Signal Lines • Drive Test signals on VME B Row pins. • Scope Ch. 1, Pin 23 (D24), Color Yellow. • Scope Ch. 2, Pin 25 (D26), Color Green. • Scope Ch. 3, Pin 24 (D25), Color Purple. • Pins 23 and 25 are driven at slot four by a 74F241 (VME spec.) and properly terminated at each end of the backplane. • Pin 24 (Channel 3) not driven but terminated.

  7. Bicc-Vero VME J2 Backplane Scope view from slot 12 (slot 9 (halfway) from slot 4, the driven slot). • File Name: • BLMBKPLN01.TIF • Channel 3 sits • at a DC level of • about 3.0 Volts. • Peak on transients • measure around • 820 mv.

  8. RAD Engineering VME J2 Backplane Scope view from slot 12 (slot 9 (halfway) from slot 4, the driven slot). • File Name: • BLMBKPLN04.TIF • Channel 3 DC • level is ~3.0 V. • Transients are ~380 mv. • This is less than half of the Bicc-Vero Backplane.

  9. Bicc-Vero VME J2 Backplane Scope Screen Dump viewed from slot 21 (last slot). • File Name: • BLMBKPLN02.TIF • With Channel 1 Overshoot and Preshoot measurements displayed.

  10. RAD Engineering VME J2 Backplane Scope Screen Dump viewed from slot 21 (last slot). • File Name: • BLMBKPLN06.TIF • With Channel 1 Overshoot and Preshoot measurements displayed.

  11. File Name: BLMBKPLN03.TIF Pattern Generator period decreased to 50ns from 100ns. Channel 1 Overshoot and Preshoot measurements displayed. Bicc-Vero VME J2 Backplane Scope Screen Dump viewed from slot 21 (Last slot).

  12. File Name: BLMBKPLN07.TIF Pattern Generator period decreased to 50ns from 100ns. Channel 1 Overshoot and Preshoot measurements displayed. RAD Engineering VME J2 Backplane Scope Screen Dump viewed from slot 21 (Last slot).

  13. RAD Engineering VME J2 Backplane • How would a fully loaded backplane affect the level of crosstalk seen on the signal line? • How to simulate a fully loaded backplane? • Slots 5-11 and 13-21 have a 18pf capacitor installed on the B Row between pins 22 (GND) and 23 (D24) • Simulated load is: 16 x 18pf = 288pf • VME spec. is: £ 20pf per slot (For Add/Data)

  14. File Name: BLMBKPLN08.TIF Simulating a fully loaded backplane. Channel 1 Overshoot and Preshoot measurements displayed. RAD Engineering VME J2 Backplane Scope view from slot 12.

  15. File Name: BLMBKPLN09.TIF Setup same as BLMBKPLN08.TIF Except: Pattern Generator period decreased to 50ns from 100ns. RAD Engineering VME J2 Backplane Scope view from slot 12.

  16. File Name: BLMBKPLN10.TIF Simulating a fully loaded backplane. Slots 5-20 have a 18pf capacitor installed. RAD Engineering VME J2 Backplane Scope view from slot 21.

  17. File Name: BLMBKPLN11.TIF Setup same as BLMBKPLN10.TIF Except: Pattern Generator period decreased to 50ns from 100ns. RAD Engineering VME J2 Backplane Scope view from slot 21.

  18. Comparison Summary • Bicc-Vero VME J2 Backplane • Crosstalk Amplitude = 820 mv. • RAD Engineering VME J2 Backplane • Crosstalk Amplitude = 380 mv. • The RAD design uses many ground isolation islands between parallel traces. • RAD Engineering Backplane Design appears to minimize the level of crosstalk.

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