Advanced Tech: Sony STARVIS 2

Been exploring some image sensor tech and Sony’s STARVIS 2 line up looks great. It’s the second-generation “starlight-vision” CMOS tech that runs on many of today’s best low-light security and automotive cameras. They’re impressive because they significantly improve low-light performance, capturing clear images even in near-total darkness. STARVIS 2 delivers higher sensitivity, better dynamic range, and superior near-infrared capture, all without increasing pixel size.

Starvis Camera Sensor
Starvis Camera Sensor

The first STARVIS sensor came out a decade ago, using back-illuminated pixels. This change alone made sensors about 4.6 times more sensitive. Then, in 2021, STARVIS 2 took it further with new tech: deeper vertical photodiodes (not wider, which most companies do) and dual-gain HDR. Deep buckets (vertical photodiodes) extend straight down into the silicon, so they store many more photons without overflowing. IR light penetrates further into silicon before it’s absorbed, so more IR photons are caught. These improvements boost dynamic range by over 8 dB, meaning sensors can clearly capture bright and dark areas simultaneously without blur.

Applications range from security cameras that clearly identify faces at night, traffic cameras capturing license plates in headlights, to dash cams and drones with great low noise performance. So for a normal user purchasing dash cams, make sure you buy once with STARVIS 2 to ensure you can see number plates in bright and low lights. Of course, Sony isn’t alone. They have competitors like OmniVision’s Nyxel, Onsemi’s Hyperlux, and Samsung’s ISOCELL Auto, but Sony is ahead.

Interviews with Sony folks hints at sensors that eliminate the need for shutter exposure times and LED flashes entirely, capturing details from bright sunlight to starlight. This might suggest even deeper wells or some new stacked-pixel designs are on the horizon. Imaging tech will be a nice place to be in when AI robots take off in the next 5yrs.

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Back to Basics: AC Coupling in High Speed Lines

I was doing some high speed PCB designing and thought AC coupling capacitors that are placed on high speed differential lines might be a good topic to discuss today. These are series capacitors you will see placed in USB 3/4 lines, PCI Express, HDMI etc.

Like any capacitor, at DC, it’s an open switch, at high frequency, it’s a dead short. Why do you need it? It blocks any DC voltage. Every differential link has two voltages: the desired differential swing (like +/-400mV) and an unwanted but expected common-mode voltage that both wires sit on, measured with respect to ground. The series capacitors block the DC part, letting each side of receiver/transmitter to coexist without any issues.

Series AC Capacitors

If there is any small ground offset(in mVs) between two sides, it would push a continuous long term DC current and waste power. Coupling caps block them. It also allows for hot plugging. Meaning if one side is powered, the other side is off, without any series capacitors, live driver will push DC current straight into pins that are still at 0 V, which is bad. By inserting series caps, you ensure no DC flows until both ends are fully powered and switching.

How to choose one? Most specs put cap values between 75nF and 220nF. With the 100Ω termination, that puts the high-pass freq in the tens of kilohertz, well under the spec to pass gigabits of data. I usually prefer using 0201 type capacitors, purely because they are small(low inductance) and they fit the differential pair lines width without majorly spacing it out. Placement matters. I place one cap in each leg, side by side, same orientation, pads inline, so the pair runs straight through. Keep stubs under half a millimetre and return to 100 Ω within a millimetre. Most spec/chips will tell you what you need to do.

Please take care of them while routing. They look tiny but if you get their placement or value wrong and your gigabit link will fail. It’s hard to debug them unless you have some high-end oscilloscopes. So treat them well.

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