IWR6843: RTRIM Values and the APLL -- What do all the fields mean / do?

Alex Byrley

Part Number: IWR6843

The RTRIM API User's Guide shows us how to change the value of the RTRIM value within TI millimeter wave devices. It suggests the following:

rlRfApllSynthBwControl_t ctrlArgs;
int32_t retVal;
memset(&ctrlArgs,0,sizeof(rlRfApllSynthBwControl_t));

ctrlArgs.synthIcpTrim = 1;
ctrlArgs.synthRzTrim = 8;
ctrlArgs.apllIcpTrim = 0x26;
ctrlArgs.apllRzTrimLpf = 0x9;
ctrlArgs.apllRzTrimVco = 6;

retVal = (int32_t)rlRfApllSynthBwCtlConfig(RL_DEVICE_MAP_INTERNAL_BSS, &ctrlArgs);
if (retVal < 0)
{
System_printf("An Error Occured!");
}

System_printf("Trim: %d\n",rtrim_get());

----------------------------------------------------------------------------------------------------

Question:

Can someone tell me what the fields:

ctrlArgs.synthIcpTrim
ctrlArgs.synthRzTrim ;
ctrlArgs.apllIcpTrim
ctrlArgs.apllRzTrimLpf
ctrlArgs.apllRzTrimVco

are doing? What do they represent / why should we change them? Also -- why are these values suggested?

Thanks!

over 2 years ago

0 CHETHAN KUMAR Y.B. over 2 years ago

TI__Mastermind 25835 points

Hello Alex,

These are APLL parameters. mmWave sensor has APLL to generate high frequency clocks in the system. PLL has internal VCO that generate 14.4GHz frequency.

In some cases, these frequency and it's harmonics (28.8GHz) could emit spurious emissions, to reduce thiese emissions there are trims provided. These are trimming bits related to VCO, charge pump, low pass filter parameters..

To understand bit more implication of these trimms you could refer to below appnote section 5.3.

https://www.ti.com/lit/an/spracp3c/spracp3c.pd.

RTRIM update procedure in the below link.

https://dev.ti.com/tirex/explore/node?node=A__AOOMiif1IwuhC4VXPf18sA__com.ti.mmwave_industrial_toolbox__VLyFKFf__LATEST

These trims helps to pass the world wide regulatory compliance limits.

Thanks and regards,

CHETHAN KUMAR Y.B.

0 Alex Byrley over 2 years ago in reply to CHETHAN KUMAR Y.B.

Intellectual 465 points

Yes I have seen that but I would like to know what each of these fields do so I can predict performance changes. For example, what happens when I change ctrlArgs.synthRzTrim ? How is that different from ctrlArgs.apllRzTrimVco? What effect does changing ctrlArgs.apllRzTrimLpf have? Etc. If I knew what each field was controlling, I could answer these questions.

+1 CHETHAN KUMAR Y.B. over 2 years ago in reply to Alex Byrley

TI__Mastermind 25835 points

Alex Byrley,

These are APLLs loop control parameters, they are selected after careful study of PLL design optimization, considering best from the emission, Phase noise, PLL locking behavior, transient/steady state performance etc. over process, voltage and temperature on large number of parts. And they are not recommended to change by the customers.

We do not recommended changes to these values. If there are issues relating to the PLL/Synthesizer that doesn't meet any of the Radar system parameter let us know.

Thanks and regards,

CHETHAN KUMAR Y.B.

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IWR6843: RTRIM Values and the APLL -- What do all the fields mean / do?