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Forum: µC & Digital Electronics Battery supply for microcontroller CC2652R1


von VV V. (vivi)


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Hi,

I have programmed the microcontroller CC2652R1 using a development 
board. Now I want to produce my own PCB board with a battery as power 
supply.
The Manual of the µ-Controller says that it has a supply voltage range 
of 1.8-3.8V. Now I am not sure what volage is realy needed. In the 
manual there is no hint in what case I need what valtage.

I was thinking of using a rechargable 3.7V battery. Do I have to use a 
voltage regulater to convert the voltage to e.g. 3.3V as it was done in 
the development board? Or can I use the battery as it is, because its 
3.7V are still in the range of 1.8 and 3.8V?

Is it better to have a low or a high supply voltage regarding a 
low-power application?  Would it be advisable to just use battery with 
less voltage (e.g. 1.8V)

I will be happy about any suggestions.
Thanks

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von K. S. (the_yrr)


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VV V. schrieb:
> Or can I use the battery as it is, because its
> 3.7V are still in the range of 1.8 and 3.8V?

A rechargeable Li-Ion/Poly has a voltage range of 4.1/4.2 down to maybe 
3 to 2.5 volts, depending on how much you discharge it.

von Stefan ⛄ F. (stefanus)


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The datasheet of CC2652R1 gives clear information in table 5.3 
"Recommended Operating Conditions". It runs fine with 1,8 - 3,8 Volt.

Lower voltage brings lower energy consumption. Don't forget that the 
nominal voltage of a battery depends on the technology and charge state.

Two 1,5 V alcaline cells have 1,8 - 3,2 V.

A reachargeable Lithium cell has 3 - 4,3 V, which is too much, so that 
requires a voltage regulator.

: Edited by User
von VV V. (vivi)


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Thanks a lot.

> A reachargeable Lithium cell has 3 - 4,3 V, which is too much, so that
> requires a voltage regulator.

So to what voltage should I regulate it down?

von Stefan ⛄ F. (stefanus)


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VV V. schrieb:
> Thanks a lot.
>
>> A reachargeable Lithium cell has 3 - 4,3 V, which is too much, so that
>> requires a voltage regulator.
>
> So to what voltage should I regulate it down?

Something between 1,8 and 3,8 Volt - obviously.

I assume that there is more than this single microcontroller, so you 
should check the requirements of the other parts as well. In case of 
doubt, use 3 Volt. Because that's a common standard within the allowed 
range.

Be careful with the selection of the voltage regulator. This device has 
an RF interface, which usually means that all they consume short peaks 
of much more current than written in the datasheet. You need a voltage 
regulator that can follow these peaks quickly enough. Also you possibly 
want to reduce the standby consumption to a minimum. Only some few 
voltage regulators support both together.

The HT7830 is one of them.

: Edited by User
von VV V. (vivi)


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Thanks a lot for your explainations.


> I assume that there is more than this single microcontroller

Not really. I am using the Controller to get sensor data. So I don't 
have any other parts in my circuit till now.


> You need a voltage
> regulator that can follow these peaks quickly enough.

What is the aspect in the datasheet which tells me, that it can follow 
quickly enough?
During sending, my device consumes 11mA and usually an average of 2mA.

von stefanus (Guest)


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VV V. wrote:
> What is the aspect in the datasheet which tells me, that it can follow
> quickly enough?
> During sending, my device consumes 11mA and usually an average of 2mA.

You wont find that in the datasheet. You need to make your own 
measurements in the target circuit. Some chip manufacturers provide 
separate documents that tell you how to design PCP and power supplies 
properly.

von stefanus (Guest)


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To give you an impression what I mean with peaks in the power consumtion 
take a look at this website: 
https://www.ondrovo.com/a/20170207-esp-consumption/

This WiFi microcontroller is specified for average 70 - 80 mA in active 
mode but it consumes up to 435 mA while sending. You 11 mA are surely 
also an average value which does cover these peaks.

von VV (Guest)


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> You 11 mA are surely
> also an average value which does cover these peaks.

I did measurments and this is the maximum current it reaches. See the 
attached image. Average value 2mA, peak 11mA.
The specification in the datasheet says it takes 9.6mA when 
transmitting.
I only have these measurments and I thought I could trust them.

So what qould you recommend?

von stefanus (Guest)


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I assume that you did not measure properly. The peaks are so short that 
you cannot even see their waveform. You need to measure them with a much 
shorter time base.

von stefanus (Guest)


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I saw in the datasheet that the RF output power of that chip is only 5 
dBm which is about 3.2 mW. This is far less than I assumed, so your 
measurement might be Ok.

Anyway you still need a voltage regulator that can handle the peaks 
quickly enough, or the voltage would become unstable. Many Low-Drop 
regulators are slow, keep that in mind.

As I wrote, the HT7833 can be used.

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