Simplifying IoT: Nordic Launches Its “First” PMIC for nRF SoCs
Nordic Semiconductor has taken its next step towards being a one-stop solution to IoT design by introducing its first PMIC, the nPM1100.
Nordic Semiconductor has joined other major manufacturers of advanced electronics to offer a power management integrated circuit (PMIC).
The nPM1100 is Nordic Semiconductor’s first PMIC. Image used courtesy of Nordic Semiconductor
This article will break down the specifications of the nPM1100 concerning interfacing to the Nordic nRF MCUs and look at the nPM1100 evaluation kit (EK). Finally, the new WLCSP PMIC will be compared to other industry options to see if any unique features make Nordic's option more appealing over others.
The nPM1100's Key Performance Specifications
The nPM1100 is a single input, dual output PMIC capable of delivering selectable voltage ranges for both an unregulated system rail and a regulated buck converter fixed at 150 mA, powered either by a USB interface or a Li-ion/Li-Polymer battery pack (with its JEITA-compliant charger).
The nPM1100 PMIC block diagram. Image used courtesy of Nordic Semiconductor
The PMIC includes an essential feature for the long-term health of a secondary cell battery. The feature is how the charge rate can be varied, based on resistor selection, from 20 mA to 400 mA. Varying charge rates can be a significant determinant of Li-ion longevity.
Finally, Nordic highlights two key features of the nPM1100:
- An ultra-low quiescent current (470 nA) in “ship mode”, or 700 nA without ship mode enabled.
- Interfacing with the nRFx families, the PMIC bypasses the SoC regulators, increasing overall available system power by 10 mA to 100 mA.
These two features help provide system power budget advantages, which are essential to any platform but critical for IoT devices' usefulness.
After looking at some of the key specs of this PMIC, an important question is how it interfaces with Nordic Semiconductors flagship products?
Powering Nordic’s BLE nRFx Microcontrollers
Although designed for a 2-layer board stack-up (which can result in significant cost reduction), Nordic acknowledges that the nPM1100 likely requires a 4-layer board and micro-vias to support ship mode.
This limitation can be something of a misnomer, though, for two reasons: 2-layer boards are typically uncommon in the industry, and interfacing the nPM1100 with an nRF5340 95-pin microcontroller could require more than 2-layers.
Below is an example interface between the nPM1100 and generic nRFx module.
An application circuit example for the PMIC and nRFx MCUs. Image used courtesy of Nordic Semiconductor
Pins D4 & D3 are the control signals for the ultra low-IQ ship mode. There are two methods to disable ship mode: connecting the USB VBUS or pulling SHPHLD (D3) low via a push-button.
Now that an understanding of how this PMIC might power Nordic's MCUs, a look at the evaluation kit for the nPM1100 PMIC might help shine further light on this PMIC.
Nordic Semiconductor’s nPM1100 Evaluation Kit
The evaluation kit for Nordic’s first PMIC product. Image courtesy of Nordic Semiconductor
The PMIC kit breaks out all of the pins on the nPM1100 for access and testing purposes. DIP switches control the functionality of ship mode, charger termination voltages, regulator output voltages, and several other parameters.
After considering the evaluation kit's features, engineers could be asking whether there are existing industry PMICs with similar characteristics to the nPM1100?
Industry PMIC Options for IoT Technology
A parameterized search of Maxim Integrated PMIC (one possible PMIC vendor) components shows that PMICs vary significantly in complexity in terms of features and the number of output rails.
Searching for JEITA certified, USB interfaced, battery charging PMICs in the voltage range of the nPM1100 reveals six wafer-layer packages and two QFNs.
For example, the MAX20345 is a low IQ (550 nA) PMIC for li-ion systems. However, instead of a single buck output, it has three. Additionally, it has three LDOs.
In comparison, the nPM1100 offers relative simplicity and minimalism—vital elements to mitigating cost in an IoT device requiring a limited number of voltage rails. Also, the ability to lower the IQ of the system to 470 nA in ship mode could provide an advantage over other options.
With each of the features mentioned above, it seems that this PMIC is beneficial to IoT applications and could help further IoT technology by helping to simplify power systems.
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