Mesh SoM’s HW feature request (power management)

Connectivity BLE // NFC
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I really like where Particle is going with their products and want to make use of the new announced devices as soon as possible. I only miss one key feature though.

I would like to see some more flexibility in the power management side of the hardware. Not everyone has the same power requirements for their use case / product.

Let’s get technical. The Electron/E series hardware does have a nice PMIC chip (BQ24195) onboard. For as far as I know, the new mesh devices will have the same PMIC configuration.
The problem is that those PMIC chips are implemented in a way that are not very accessible to the end user. This really limits the integration into an end product.

The purpose of a PMIC chip should be to centralize all power management into one smart chip that coordinates all sorts of power flows for the entire system / product.

I will demonstrate my point with a simple example of product requirements.

  • Li-ion battery 6000mAh - 11000mAh 1cell
  • Powered by 5V or 12V adapter
  • Or powered by descent 10W solar panel (has 8-9V at Pmax)
  • Needs 5V peripherals power support besides 3V3
  • Cellular connectivity
  • All above requirements with lowest power loss and components count in mind

In this example I would like to generate the 5V power from the SYS pin (BQ24195). I could generate it from the 3V3 output, but this is not very efficiënt. Besides, if I pull to much current or a transient, I could brown out the uC. I would like to avoid this at all cost.
Unfortunately this SYS pin is not exposed to the end user, even the E series does not provide access to this pin.

Another example is the solar panel. I would like to connect it with as few extra components possible. I could connect it to Vin (Electron), the BQ24195 supports voltages up to 17V and even has “input voltage DPM regulation” feature. But with solar you want to extract power at optimum voltage, in my case around 8-9V. The DPM feature can only be configured to max 5.08V (Vindpm), way below operating conditions.
In this case I would like to use a more suited PMIC, the BQ25895 is almost the same as BQ24195 but is way better suited for solar power.
At least I would like to bypass the onboard BQ24195 and implement my own power solution in this case.

Let’s end it here for now :).

Sam

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The SoM devices do not include the power supply on the module, so you’re free to use different PMICs, regulators, etc. that are best suited for your application.

4 Likes
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Ah, this is great news, I assumed the HW setup would be more like the Electron E series boards.

Do you already have a pinout for these SoM boards? And if the SoM’s don’t have power circuits onboard, do we need to provide both 3.3V (for uC) and ~3.8V (for Cellular)?

I pre-ordered some new Mesh devices and can’t wait until they arrive ;).

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The pinouts are not available yet. However there will be multiple power pins, such as 3.3V, a module power pin (for the cellular module, for example), analog reference, and RTC backup power (not final, subject to change).

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