Back to Basics: RRAM

Posted under Back to Basics, Tech Explained, Technology on August 3rd, 2025 by

I was looking up on the latest microcontrollers and noticed something interesting, the tech behind the non-volatile memory used to store code is shifting away from traditional Flash memory. When I read more, I saw it’s being replaced by something called RRAM (Resistive Random Access Memory). Thought I’d share about that today.

Resistive RAM

It’s essentially a very simple memory that stores data by changing resistance in a tiny metal-insulator-metal structure. An applied voltage creates microscopic conductive filaments, toggling between high and low resistance states for storing 1 or 0 permanently.

But why the shift away from Flash memory? Flash has been in embedded applications for a long time, but it struggles below roughly 28nm process nodes. Below these nodes, Flash integration gets complicated and expensive because of multiple extra masking steps, and isn’t naturally compatible with newer FinFET transistor technologies. That’s one reason why you see some microcontrollers not having on chip flash memory and rely on external flash chips like RPI Pico series. Flash still offers proven reliability and high density for nodes above 28nm.

RRAM uses a simpler structure that’s easily integrated into advanced FinFET nodes below 10nm. This drastically simplifies system design, reduces costs, and saves board space. RRAM is also better than Flash in many areas. It writes data at around 10ns, supports multi-level storage for greater density, similar data retention time(>10yrs) and consumes much less power. These make RRAM ideal for embedded uses, like firmware updates, fast booting, data logging, and sensor data storage in IoT and automotive systems.

Personally, I think the shift towards RRAM is great because it brings the best features of Flash and DRAM by combining non-volatility with high speed, scalability, and energy efficiency.

BTW: The energy needed to switch a single bit in RRAM is just a few femto-joules. That’s roughly the same energy our brain uses to fire a single synapse. Low power indeed.

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Back To Basics: Speakers and Power Levels

Posted under Back to Basics, Educational, Technology on July 6th, 2025 by

Was discussing a project with a client when they mentioned needing a “5-Watt” speaker for their product. I asked how they arrived at that number, and they said they’d used one previously and liked its loudness. I want to clarify a common mistake folks make. More Watts Doesn’t Always Mean More Volume. In fact, Watts might not even be the right way to choose a speaker. Let’s discuss this.

Speaker Sound Level

Speaker loudness is actually measured by Sound Pressure Level (SPL), expressed in decibels (dB), not watts. Watts only indicate how much electrical power a speaker can handle. SPL tells you how loud a speaker will get at a given distance and power input. Specifically, speaker sensitivity measures loudness in decibels at 1 meter away using just 1 watt of input. This is your real guide for loudness, and you will find this value in good speaker datasheets.

To get just a 3dB increase in volume, you must double the power. So, if one speaker has a sensitivity rating of 90dB and another is rated at 80dB, the first speaker is significantly louder at the same wattage. For instance, a 50-watt speaker with a 90dB rating will outperform a 100-watt speaker rated at 80 dB. Why? Because the higher sensitivity speaker converts electrical power into sound more efficiently.

SPL(dB) = Sensitivity(dB) + 10 log(Power)
  For the 90dB speaker at 50W : 90 + 10 log(50) = 90 + 16.99 ≈ 107dB
  For the 80dB speaker at 100W: 80 + 10 log(100) = 80 + 20 = 100dB

Remember, sound decreases by approximately 6dB each time the distance doubles, so you use this a tip to estimate levels at longer distance from the speaker. A speaker producing 90dB at 1m drops to about 84dB at 2m.

BTW fun fact, humans perceive a 10 dB increase as roughly twice as loud, but this actually requires about ten times more power.

So next time you’re selecting speakers, first check the sensitivity rating (dB/W/m) and not Watts alone.

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