The Rollercoaster ride of Bringing Up a Gigabit PON CPE Chip- An experience of lifetime.
Post-silicon validation is where design models meet reality, a phase filled with anticipation, anxiety, and moments of pure exhilaration. In this blog, I’ll take you through my personal journey of bringing up a 48-pin Gigabit PON CPE chip back in 2005-2006. Despite passing all pre-silicon checks, simulation regressions, STA closure at all corners, and physical design signoffs, the real test began the day the chips arrived and were mounted on our validation board. Here’s how it unfolded.
1. From Simulation Confidence to Silicon Reality
We had every reason to be confident. Our simulations were flawless, timing was closed, and signoffs were green. But the moment those silicon chips arrived in their anti-static packaging, our confidence suddenly felt theoretical. Mounting them on the test zig, specially soldered onto the validation board, felt like sending your child to their first day of school, proud but terrified.
The validation board was designed with:
Our toolkit was ready:
2. A Journey of Highs and Lows
I'll never forget the collective gasp in the lab when we first applied power. Four of us stood around the validation board, multimeters in hand, watching for magic smoke. When the DMM showed clean readings with no shorts, the relief was palpable. We'd passed our first real-world test, a small but significant victory that set the tone for the months ahead.
The day the 25 MHz crystal refused to generate a clean 125 MHz clock was one of our lowest points. For two agonizing days, we probed, measured, and debated while the entire company waited for updates. The breakthrough came at 8 AM when we discovered a capacitor value mismatch on the oscillator circuit. That moment of discovery, and the perfect square wave that followed was worth every stressful hour.
The loopback tests became our daily emotional rollercoaster. I remember one day when the PON-level loopback failed for the 13th consecutive time. Just as frustration peaked, our board designer noticed a switch setting we'd all overlooked. The cheer that erupted when packets finally looped successfully could be heard across the entire floor!
Configuring the protocol analyzer as a CO system felt like preparing for a space docking maneuver. The byte-order confusion had us questioning our design choices, but the configurable endianness option saved us. When we finally achieved handshake, the lab erupted in applause. Someone brought out a hidden bottle of champagne they'd been saving for this moment, we celebrated like we'd just landed on the moon.
Daily status meetings became theatrical performances. I developed a "good news sandwich" approach: start with progress, carefully present challenges, and end with solutions. The time I had to explain why the laser delays were off by 3 nanoseconds to 3 Bosses remains one of my most memorable professional moments. Their collective gasp when I showed the fix work still makes me smile.
The day all subsystems worked in harmony remains etched in memory. The perfect symphony of:
We ordered pizza for the entire team and stayed late just to watch the protocol analyzer show perfect traffic patterns. In that moment, every sleepless night felt worth it.
Using DMMs to verify no shorts between power rails (1.1V and 3.3V) and ground, ensuring voltage levels within tolerance (±5%), and confirming current draw within limits.
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With the 25 MHz crystal reference, achieving stable 125 MHz clock generation through careful oscillator circuit tuning and signal generator alignment.
JTAG-based programming validation register, overcoming board-level switch setting issues and internal configuration mismatches through iterative debugging.
Digital PON-Level Loopback: GPON-specific traffic validation
UNI-Level Loopback: User-network interface testing, Each requiring meticulous switch configuration and register tuning
Critical achievements included:
Finally, comprehensive testing included the following:
These were carried out one by one.
The ability to maintain composure during setbacks separated successful validation from failure. The emotional Resilience Matters.
Regular, honest updates-built trust and turned pressure into collective problem-solving. Transparent Communication is most important during stressful times.
Each milestone, no matter how small, deserved recognition and boosted team morale. Celebrate Small Wins.
Our detailed logs became invaluable for future projects and new team members. Document Everything.
The best technical solutions emerged from collaborative debugging sessions. Teamwork yields success.
Why This Experience Still Matters
Twenty years later, I remember every detail of this bring-up because it was more than technical validation, it was human achievement. The late nights, the breakthroughs, the shared frustrations and triumphs created bonds that lasted throughout our careers. That Gigabit PON CPE chip wasn't just silicon; it was a testament to what a dedicated team can overcome together.
The experience taught us that while simulations prepare you for what should happen, real character is built handling what happens. And that's a lesson no simulation can ever teach.
What's your most memorable validation story? Share your experiences and lessons learned in the comments below!
"Brilliant storytelling! Post-silicon validation is as much an emotional journey as it is a technical one — power-ups, stable clocks, loopback wins. This resonates strongly with what we see in our own work at Theta90."