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WICED Smart Bluetooth

StBa_721356
Contributor

What are the real power consumption advantages when using external oscillator?

We noticed in our tests that when using an external oscillator the power consumption in deep sleep gets reduced by about 3.5µA at 1.7V. Is this to be expected?

What other effects would an external oscillator have beside the higher accuracy of the RTC?

Are there any 'hard numbers' available?

Does the external oscillator has any effect on the infamous Crystal Warm-Up issue?

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1 Solution
Anonymous
Not applicable

Hello Stefan,

From the developers:

1.  Yes, you should see power consumption improvement using the external oscillator.

2.  We have not run the power consumption tests with the external oscillator at 1.7V.

3.  The external oscillator does not have any effect on the Crystal Warm-Up Issue

4.  In sleep we turn off the Internal LPO.

5.  Since the use of the External LPO is more accurate you will see a power savings

6.  For longer connections it will be more accurate and better power savings.

7.  You should see sleep current drop between 5 to 6 uA if you used an External LPO.

Thanks,

JT

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4 Replies
Anonymous
Not applicable

Hello Stefan,

From the developers:

1.  Yes, you should see power consumption improvement using the external oscillator.

2.  We have not run the power consumption tests with the external oscillator at 1.7V.

3.  The external oscillator does not have any effect on the Crystal Warm-Up Issue

4.  In sleep we turn off the Internal LPO.

5.  Since the use of the External LPO is more accurate you will see a power savings

6.  For longer connections it will be more accurate and better power savings.

7.  You should see sleep current drop between 5 to 6 uA if you used an External LPO.

Thanks,

JT

View solution in original post

Anonymous
Not applicable


Hi

Is it same when we use BCM20736S external oscillator power consuption can improved?

Thanks,

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MichaelF_56
Moderator
Moderator

The SIP Module includes a standard 24MHz Pierce oscillator (handles System/RF)

The module also supports an external 32KHz LPO Oscillator

Since the internal LPO runs at 128KHz, one would expect higher dynamic power.


External Oscillator therefore in theory = Better sleep clock accuracy & lower sleep current of about 20% rough estimate the developers provided me during discussion, but never measured)


The theory is that the Ext Osc is utilized when increased sleep clock accuracy (PPM) is needed.  Recall that as part of the connection event, the master and slave exchange sleep clock accuracy (PPM) and the accuracy is used to determine the uncertainty window of the slave device for the duration of the connection event. This means that more accurate clocks can actually save power.

As mentioned previously, we are working both internally and with Partners to develop some boards which will address our lack of a good power measurement platform (and associated profile/application as this peice is every bit as important since Bluetooth is so configurable).  We should have something announced in the community soon.

jasonc ndutton

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Anonymous
Not applicable

Stefan,

You may also want to take a look at the new TruConnect features. We added a number of power mode options to that today also.

TruConnect 1.5 for BLE Released Today

Nick

ACKme Networks

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