SLIDE 1
Content
1
Gigabit Serial Link
2
Test Setup
3
Results
germic@physik.uni-bonn.de 2 / 12
Bit Error Rate Test of DHPT 1.0 Gigabit Serial Link Leonard Germic , - - PowerPoint PPT Presentation
Bit Error Rate Test of DHPT 1.0 Gigabit Serial Link Leonard Germic , - - PowerPoint PPT Presentation
Bit Error Rate Test of DHPT 1.0 Gigabit Serial Link Leonard Germic , Carlos Marinas, Hans Krger and Norbert Wermes germic@physik.uni-bonn.de University of Bonn today, 2014 Content Gigabit Serial Link 1 Test Setup 2 Results 3
SLIDE 2
SLIDE 3
Gigabit Serial Link of DHPT 1.0
Facts: 1.6 GHz differential output programmable preemphasis
- ff-chip 100 Ω matching resistors
1.2 V domain (VDD_CML, core voltage)
germic@physik.uni-bonn.de 3 / 12
SLIDE 4
Why preemphasis
Compensation of the attenuation of high frequency regime in the signals spectrum due to long distance transmission
Increasing bandwidth Preventing single bit error Figure: Signal spectrum with preephasis.
germic@physik.uni-bonn.de 4 / 12
SLIDE 5
Signal generation
Preemphasis realization: Subtraction of signal S1 with delayed signal S2. Two 8 bit DACs IDAC_CML_TX_BIAS and IDAC_CML_TX_BIASD One 2 bit DAC pll_cml_dly_sel S1(t) S2(t) S2(t + dt) S1 − S2(t + dt)
germic@physik.uni-bonn.de 5 / 12
SLIDE 6
Implementation
Current Mode Logic Driver with programmable preemphasis Three parameters:
IDAC_CML_TX_BIAS, IDAC_CML_TX_BIASD, pll_cml_dly_sel Same values of IDAC_CML_TX_BIAS and IDAC_CML_TX_BIASD do not correspond to same currents/differential voltage swing (differently sized current mirrors)
germic@physik.uni-bonn.de 6 / 12
SLIDE 7
BERT Test setup
1x Evaluation board XUPV5 − LX110t as DHH emulator 1x Evaluation board XUPV5 − LX110t as Bit Error Rate Tester (IBERT, Xilinx) 2x 15 m Infini band cables ... and a crazy ’handmade’ script
germic@physik.uni-bonn.de 7 / 12
SLIDE 8
Figure: BERT Test system. Top board = DHH emulator, Buttom board = IBERT (Xilinx).
germic@physik.uni-bonn.de 8 / 12
SLIDE 9
BERT Results - Good A and bad B case
A B
Figure: Red line indicates the BERthr of 10−6
germic@physik.uni-bonn.de 9 / 12
SLIDE 10
Optimal Working Point
A B
Figure: Sweep results at a threshold of BERthr = 10−6. Higher is better - wider opening at BERthr
germic@physik.uni-bonn.de 10 / 12
SLIDE 11
Optimal Working Point
BEST
Optimal working point BIAS = 15, BIASD = 150, dly = 0.
germic@physik.uni-bonn.de 11 / 12
SLIDE 12
Thank you for your attention!
germic@physik.uni-bonn.de 12 / 12
SLIDE 13
Sweep test
These are NOT absolute BER values. NMOS of current mirrors saturate above DAC values ∼ 150 (Design bug)
Figure: Plateau due to saturation of the current mirrors.
germic@physik.uni-bonn.de 12 / 12