I CANNOT USE nPM 2100 EK WITH CR2023

Question

Hello 
 nPM Power UP v 2.24 detects nPM2100 EK, but does not detect the CR2032 battery. The active battery model selected is CR2032 and the fuel gauge is enabled. 
 I placed the CR2032 in the battery holder and connected it to Battery Input Connector on EK. 
 Two LEDs light up side by side: a red LED and a yellow LED. 
 I tested it with SW5 for VEXT and VBAT. 
 I have read this link. www.nordicsemi.com/.../Get-started 
 Regards 
 Luiz Miranda

Szabolcs · Accepted Answer

Hi Luiz, 
 from what I can see from the pictures, the battery holder is connected the wrong way around. Please break the PCB out of the panel and connect it with the battery holder facing upwards (so that all the rubber pads are on the same side).

Szabolcs · Answer

Hi Luiz, 
 I'm glad to hear that it works. I'm afraid we don't have a ready solution to connect CR2450 to the EK. I think the best way would be to buy a battery holder and use jumper wires to connect to the input. You can use the CR2032 fuel gage model, as the chemistry of these batteries are identical.

Szabolcs · Answer

Hi Luiz, 
 we can help, yes. What exactly is the problem, where did you get stuck? Can you share the schematic?

Szabolcs · Answer

Hi Luiz, 
 We don't have much experience with using piezo buzzers, especially together with nPM applications. This is not a very common use case, so we rarely see projects like this. I will try to answer your questions as best as I can, but keep in mind, that these are just my professional opinions and could have some mistakes. 
 Luiz Miranda said: What are the official recommendations for the driver circuit topology (e.g., migrating to an N-channel MOSFET like the 2N7002, an H-bridge configuration, or sticking with a standard BJT) to safely and efficiently achieve 80 dB at 3.0V or below? 
 A single MOSFET is of course the simplest solution, but a full H-bridge can probably achieve more output power since it drives the buzzer "both ways". Maybe the buzzer of the evaluation kit you're using has some recommendations regarding the driver. 
 Luiz Miranda said: What are the ideal values and types of bulk/decoupling capacitors (low-ESR ceramic vs. electrolytic) recommended to shield the nPM2100 power rail from the heavy current ripples caused by the 4 kHz piezo PWM switching? 
 Since the buzzer is operating for seconds, the capacitors don't really make a difference. We recommend using the reference design for the nPM. 
 The best way to go forward with this is hooking up oscilloscope to the VBAT/VOUT of nPM2100 and also measuring battery current as well as the load current during piezo buzzing and seeing what actually is going on. If for example you see the voltage sagging with the 4kHz buzz frequency, then this could be helped with additional capacitors on the VINT. How much, depends on the load. We don't know that... 
 Luiz Miranda said: Are there any specific application notes or reference designs from Nordic combining the nPM2100 and passive piezo transducers operating on high-impedance coin cells (CR2032)? 
 No, unfortunately, we don't have anything like that. 
 Luiz Miranda said: Is it possible to achieve a minimum of 80dB with the CR2032? If not, which battery would be best? CR2450, for example CR2450? 
 The piezo element you mentioned draws around 13 mA (3.3V / 250Ohm), which is kind of the limit of a CR2032 battery. A bigger coin cell could work better, as they have lower ESR, which means lower voltage drop on loading. I recommend using AAA batteries, as they have very low ESR and can be combined 2 or 3 in series to have higher voltage. 
 One alternative is having multiple CR2032 in parallel, but with that configuration you need to be careful to avoid "charging non-rechargeable batteries". That means that all batteries need to be replaced with fresh ones at once, with the same brand. If there is a difference in the charge between the batteries, one will start charging the other, and that is not generally allowed. There should be an ideal diode between the batteries and the nPM2100 to prevent the current flowing to wrong direction. There's few words about that in our nPM2100 Reverse Battery Protection application note. 
 Luiz Miranda said: An important point of reference is that the PCB will have an antenna chip and that we are aiming for a PCB with dimensions of 4.5 cm x 3.00 cm. 
 These dimension would fit 3 pcs of AAA batteries. The nRF chip and the antenna needs special care during placement and routing, so look out for that. If you have a ready schematic and PCB design, we will review it to make sure that the nPM and nRF circuits and layouts are optimal. 
 
 This is all the help I can provide you now with your project, I hope it will be useful for you. If you have any specific questions regarding Nordic products, we are happy to assist you.

Szabolcs · Answer

Hi Luiz, 
 I'm glad to hear that I could provide you with useful advice. 
 Yes, the nRF SDK and Zephyr has drivers for the nPM1300. You can configure the PMIC from the Device Tree files, and also use C functions in the library to change the configuration runtime. There are sample projects provided for the nPM1300-EK, you can see how it is done in them. You can find information for all of these on docs.nordicsemi.no . You can also use the Nordic AI (bottom right corner) to help you with generating code for your project.

I CANNOT USE nPM 2100 EK WITH CR2023

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