AWR1843AOP: Thermal Performance Concerns Using CW for Antenna Radiation Pattern Testing

Hi Matthew,

We are looking into your question. Please allow us some time to respond.

This would be for 3D antenna radiation pattern.  My understanding is that this tests for power at off-bore-sight to confirm allowable 3dB roll-off at angle from boresight.  This would be a RED (EN 301 489-51 and EN 302 264) test in this case.  So the EVM is put in CW mode for indefinite period of time w/o issue.  My understanding of CW is not chirping, it's continous wave or always ON.  NOT ON/OFF chirps.  Can you clarify?

Thanks, Blake.  Can you tell me how much power to expect the AWR1843AOP to draw when in CW mode?  I could do thermal simulations on with our product design w/ the expected power draw in Watts.

Matthew, 

I'm looking for data on this. 

I'll respond by Wednesday. 

Very Respectfully,

Blake

Blake, Sounds good!  I look forward to hearing back.

-Matthew

Great! 

Can you point me to "the functional (chirping) mode current values"?  Is this the 2.08W listed in the datasheet for 50% duty-cycle or something else?  If not, will you please point me to where I can find these values you're referring to here?

Also, as a note just because it's a mode that is not used during normal functional use doesn't mean that it's NOT required to have the AWR1843AOP be qualified.  If I want to sell a product that uses this SoC, I need to be able to pass RED and FCC testing to sell the product per regulatory compliance requirements.  As this is the case, it really doesn't make sense to NOT support and characterize the SoC in modes that are NOT required for function, but are required for regulation and sale.  What use would this SoC be to the market if you can't sell it in the US or the EU?  Think of this from that perspective in the future as your customers will need to support CW mode in order to qualify their products that use this SoC internally.

Matthew, 

In the context of simulating heating of the device for the purposes of the original question, yes i would use Table 7-4 from the datasheet. 

We have many customers who have acchieved RED and FCC compliance (and others) with the IWR1843AOP. We have also acchieved ETSI/RED compliance on our IWR1843AOP EVM. For your convienience you can find that data here:https://dev.ti.com/tirex/explore/node?node=A__APsik-GSQgj3E2oCsrWdww__com.ti.mmwave_devtools__FUz-xrs__LATEST. I'm not immediately aware of a current draw requirement as part of ETSI/RED or 47 CFR 15.209 or 47 CFR 95. I'm also a little confused here. I thought that the point of getting the current in CW mode was that you wanted to perform a simulation on potential heating from of the module during CW testing of the antenna radiation pattern during an indeterminent amount of time. Is that understanding correct? 

V/r

Blake

Your understanding is incorrect.  The need for CW mode is to conduct antenna radiation pattern testing to the RED standard.  The question is related to this testing in that antenna radiation pattern testing requires the SoC be put into CW mode for the test.  However, this question is to address concerns that if the AWR1843AOP is left in CW mode for long periods of time during testing, it may over-heat the SoC due to the power draw.  I assume the CW mode would put the SoC in an operating mode beyond the 2.08W listed in the datasheet for 50% duty-cycle.  In CW mode, which insinuates continuous, I assume would put the duty-cycle at a higher level up to 100% even.  That's why I am asking if having the SoC in CW mode risks over-heating the SoC and damaging the internals???  I thought maybe there's some extra provisions that need to be made to put the unit into CW mode for testing that requires longer periods of testing.  Will you please review and respond with this updated understanding of my question?

Matthew, 

I actually think we are on the same page here. 

I'd like to bring us back to this respose. 

Blake Kisshauer said:

there is no no limit to how long that you can keep the radar in CW mode, so long as POH and Tj limits in the datasheet are satisfied. 

The following request is the was:

Matthew Berberich said:

Can you tell me how much power to expect the AWR1843AOP to draw when in CW mode?  I could do thermal simulations on with our product design w/ the expected power draw in Watts.

The purpose of current consumption/power measurments here is to enable simulation of thermal conditions while the system is in CW mode during RED testing to ensure Tj conditions are not violated. 

In the case that you find Table 7-4 to be overly optimistic, I would recomend using the maximum current values found in Table 7-3. This would likely be pessimistic, but can be used to set a worst cast scenario. 

I hope this helps! 

V/r

Blake

Blake, Since much of the heat dissipation is related to the layout design used on our board, it probably makes sense to do a thermal simulation w/ the values you suggest from table 7-3 for a worst-case scenario.  Thank you for this information.  I took the table values provided in 7-3 and 7-4 of the datasheet to be relative to normal function and NOT for CW mode.  Therefore, I expected the power draw for CW mode to be greater than what was listed in the datasheet.  It sounds like you're saying that the values in table 7-3 would apply to CW mode in a worst-case scenario.  Is that correct?