Designing a battery-powered device, especially using a primary (non-rechargeable) battery, requires proper power regulation, minimal energy loss, and an efficient system to maximize the battery lifetime. The nPM2100 Power Management IC (PMIC), developed solely for the primary cell batteries, is aimed at achieving these goals, with its ultra-efficient boost regulator, algorithm-based fuel gauging, and various energy-saving features.
When integrating the nPM2100 into your design, it’s quite common for developers to come across various challenges and questions, whether it’s about extending the battery life, minimizing the power consumption, or ensuring an efficient and reliable operation across various modes.
To help you along your development journey with the nPM2100, we have compiled a list of frequently asked questions for developers and engineers. Regardless of the application or which Nordic SoC Series (nRF52, nRF53, or nRF54) you are working with, you can find guidance on the most common issues and topics here.
Table of Contents
Hardware design
Q: What are the main considerations for the device schematic and layout designs? Any guidance on the external component selection for optimal performance? What to do with X pin when not used?
A: Please take a look at nPM2100 Hardware Design Guidelines and nPM2100 Design Checklist for details. The nPM2100 reference designs (Altium) available on the product page are an excellent starting point for development. Here you will find example configurations for different use cases.
Q: Can I drive the SHPHLD pin with the SoC GPIO pin?
A: No. The SHPHLD pin is not intended to be controlled with the SoC GPIO pin. The SHPHLD pin has an internal weak pull-up (default) or pull-down depending on the configuration and it should be connected only to a switch or similar device. It can be left floating if not used. There should not be an external pull-up or pull-down.
SHPHLD pin has an absolute maximum voltage of 1.9V, so controlling it with, say, a 3V logic (of the GPIO pin) can cause damage to the device. When the SoC is powered off (like in ship/hibernate mode), there will be a leakage path formed through the SoC GPIO pins’ ESD diode and the SHPHLD pull-up circuitry. This leakage will deplete the battery in ship/hibernate modes.
If the SHPHLD button is to be used for purposes other than waking up from ship/hibernate modes or entering ship mode (power off button), one option is using nPM2100 to generate an interrupt when the SHPHLD button is pressed and let the SoC take action based on that.
Note that the button could also be a dual-pole type to be able to electrically isolate the SHPHLD pin from the SoC GPIO.
Q: I want to optimize the device for very low EMI. What should I do?
A: First: make sure the general design follows our guidelines described in Hardware Design Guideline document. Our reference designs provide an example of how to place additional high-frequency bypass capacitors on the Boost input/output.
Q: Is nPM2100 protected from reverse supply voltage on VBAT?
A: External physical or electronic protection is needed (e.g, PMOS) to protect the device from damage due to reverse polarity. Please see Reverse battery protection for the nPM2100 PMIC for more details on different protection methods.
Q: Does nPM2100 support battery charging?
A: No. nPM2100 does not include a battery charger. It’s used for primary cell (non-rechargeable) battery applications.
Boost converter
Q: What is the boost maximum current in ULP/LP modes?
A: There is no strict limit for this since it depends on the boost conversion ratio, output capacitor etc. If the boost is “No HP” mode, where HP mode entry is prevented, at some point, the HP mode is actually more efficient than the hysteretic ULP/LP mode. The boost can still supply the current in LP mode, but with lower efficiency. So for high load applications, the AUTO mode is better so that the boost logic will automatically select the mode for best efficiency.
Q: Why am I seeing high current peaks from the battery when the boost is running?
A: In light load conditions, the boost operates typically in hysteretic ULP mode. The boost refresh time depends on the load, and in some cases, it can be seconds between the refresh pulses. The higher the load, the more frequent the pulses are. This operation allows very low average current consumption of the nPM2100 due to having very infrequent switching activity. There will be momentary current pulses from the battery when the boost is switching and then long periods with no current drawn from the battery. It is possible to force the boost in HP mode (PWM operation), but the average current consumption in no load condition rises from 300nA to 7.2mA typically, so for coin cell battery applications, this is not usually desired.
Q: I’m getting inconsistent current readings from nPM2100 when using PPK2 to power it?
A: nPM2100 boost operates in hysteretic mode and with light load the time between pulses can be long. But the pulses can be relatively high compared to the base current and also short. This causes challenges, first of all in the measurement dynamic range (current can vary from <1uA to tens of mA) which needs auto ranging and, secondly with short current pulses the sampling rate of PPK2 (100kS/s) can become a limiting factor. Auto ranging can sometimes lose some samples and the overall sampling rate of PPK2 might not be enough to catch full refresh current waveform. To help with this you can use bigger bulk capacitor (100uF or more) on the VBAT input of nPM2100, to reduce the boost refresh current pulse amplitude and to make it longer and easier to sample.
See also nPM2100 Hardware Design Guidelines for typical current waveforms from the battery in BLE application and how external components can change the behavior.
Fuel gauge
Q: Where can I find more information about the nPM2100 fuel gauge for primary cell batteries?
A: This application note describes the integration of the nPM2100 fuel gauge solution for the rechargeable products Using nPM2100 Fuel Gauge.
Q: What battery chemistries are supported with nPM2100 fuel gauge
A: We have battery models for CR2032, AA/AAA Alkaline 1S/2S, LR44.
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CR2032 model supports Lithium Manganese CR series batteries regardless of the size since the voltage behavior is similar in these. This includes batteries such as CR1632, CR2025, CR2450, CR2477, CR123A
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AA/AA alkaline model available (1S, 2S). Note for AA/AAA form factor there are other chemistries as well and they are not supported with the alkaline model.
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LR44 battery model supports LR series coin cell batteries, LR44 used for characterization. Note silver oxide batteries (SR series) are available in the same form factor and their behavior is different and the LR model would not work.
Q: Can the nPM2100 fuel gauge handle, say, two LR44 in parallel, or do I need a custom profile?
A: Since nPM2100 uses a voltage-based fuel gauge solution, battery capacity plays only a minimal role. So you don’t need a custom profile and can continue with the available model.
Q: I’m using a different battery chemistry; can I generate the model for it myself?
A: We don’t have similar battery profiling capability for primary cell batteries as we have, for example, in nPM1304-EK for rechargeable batteries. The models developed by Nordic are done by characterizing several battery types and manufacturers to have a generic model for a certain chemistry, which would work even if the end customer changed the battery to a different manufacturer. If some battery model is not supported, please contact Nordic sales, and depending on the demand, it is possible to generate new models.
Q: How does the fuel gauge work if the PMIC sees non-continuous load with higher current spikes and the sampling rate of the fuel gauge is only once per second and it will not catch those spikes?
A: It works fine. nPM2100 is a voltage-based fuel gauge. The fuel gauge algorithm just needs VBAT measurements (and system temperature) periodically to determine the battery State of Charge.
Q: How does the fuel gauge adapt to temperature variations?
A: The nPM2100 requires battery voltage and system temperature measurements as inputs. The battery models provided with the nPM2100 fuel gauge have temperature characteristics integrated, so the gauge automatically adapts to temperature variations.
The battery model used by the nPM2100 represents the average voltage–SOC and resistance–SOC relationships derived from extensive discharge-cycle testing across multiple temperatures and various battery manufacturers under typical Bluetooth® Low Energy application loads.
Q: If the average active‑state battery current is known, can I use it as an input to the fuel gauge to improve fuel gauge accuracy?
A: Yes.
For most applications, the average current in the active state is deterministic. By configuring the average battery current during active periods, the fuel gauge can compensate for voltage drops using the average resistance values stored in the battery model. This helps the fuel gauge deliver more reliable state‑of‑charge estimates, even under varying load conditions.
For more information, see Average battery current configuration
ADC
Q: Can the ADC be configured once and continuously provide updated average readings?
A: No, the ADC on the PMIC is event-driven and hence performs one averaging sequence per trigger, and then it stops. So you need to re-trigger it each time you wish to obtain the readings. The measurement accuracy can be improved by performing offset calibration as mentioned in the System Monitor chapter of the datasheet. This calibration is not retained across resets and hence needs to be invoked after each reset/ power-up.
Q: How is the Avg16 measurement taken? Do I need DelVBAT when averaging by 16?
A: No, you don’t need DelVBAT when averaging. When the averaging by 16 is enabled, and you start your measurement, the ADC will take 16 samples automatically in a row (one sample conversion time is 100us), and once those 16 samples are measured, the averaged result can be read through the register.
Software
Q: What DTS settings are available on an nPM2100? Where do I find documentation for these DTS bindings?
A: All available DTS settings are described in the Zephyr documentation. Search Bindings index by the PMIC name. npm2100_ek.overlay file in the Zephyr repository is a good starting point for the PMIC overlay structure
Q: Can I use the fuel gauge algorithm with a non-Nordic SoC?
A: Yes - if the target SoC has one of the supported architectures (Cortex-M33, -M4, -M3), you can. Since the algorithm is currently provided as part of NCS, it has to be integrated into the development environment manually. This can be done by copying the nrf_fuel_gauge directory into the project and modifying the CMakeLists.txt to suit the needs.
Support for more architectures will be announced.
Q: Where can I find driver and API documentation?
A: We have generic drivers that are integrated into various Zephyr APIs. There are no “nPMxxxx specific” docs here, one needs to look at the following Zephyr device drivers API Reference.
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gpio
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led
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mfd (exception - has per device docs)
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regulator
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watchdog
Bare-metal:
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Github repository for npm2100-bm driver collection.
