IWR6843: LDO BYPASS config

Tom Fisher

Part Number: IWR6843

Hi,

We saw the code in the People Counting project:

/**
 * @brief
 *  Global Variable for LDO BYPASS config, PLease consult your
 * board/EVM user guide before changing the values here
 */
rlRfLdoBypassCfg_t gRFLdoBypassCfg =
{
    .ldoBypassEnable   = 0, /* 1.0V RF supply 1 and 1.0V RF supply 2 */
    .supplyMonIrDrop   = 0, /* IR drop of 3% */
    .ioSupplyIndicator = 0, /* 3.3 V IO supply */
};

And get a couple of questions:

1. What is LDO BYPASS?

2. Why is this configuration required in this project?

3. What does our hardware design team have to pay attention when designing our own board based IWR6843AOP?

Cheers,

Tom

over 4 years ago

0 Akash Gondalia over 4 years ago

TI__Guru 50240 points

Hi Tom,

Can you confirm which from which Toolbox version you are working with?

Regards,

0 Tom Fisher over 4 years ago in reply to Akash Gondalia

Expert 1440 points

Hi AG,

It's from the Industrial Toolbox 4.3.2

Cheers,

Tom

0 CHETHAN KUMAR Y.B. over 4 years ago in reply to Tom Fisher

TI__Mastermind 25825 points

Tom,

I will respond to this query in couple of days.

Thanks and regards,

CHETHAN KUMAR Y.B.

0 Tom Fisher over 4 years ago in reply to CHETHAN KUMAR Y.B.

Expert 1440 points

Hi CHETHAN KUMAR Y.B. ,

Thanks in advance.

Tom

0 CHETHAN KUMAR Y.B. over 4 years ago in reply to Tom Fisher

TI__Mastermind 25825 points

Tom,

RF blocks operates with 1V supply, this is fed through Vin13RFx supply pins.

For the Vin13RFx rails we have option to with internal LDO to generate 1V supply to the RF blocks, This LDO would support only 2 simultaneous transmitters, If there are 3 simultaneous transmitters then this this LDO will not be able to supply current needed for the RF blocks. Then LDO bypass option need to be used. Also at full load this LDO dissipates heat on chip which is also undesired. Bypassing this LDO helps in alleviating the power dissipation on chip. For lower duty-cycled cases this option is best suited where internal LDO power dissipation is minimum.

In LDO bypass option we are bypassing internal LDO and feeding the RF 1V supply directly Vin13RFx pins. And additionally we could supply PA supply (Vout_PA) directly from the external 1V supply. This option may need bit stringent supply ripple requirement as compared to internal LDO option, This could be achieved with help of external LC filters you may refer our EVM designs. Benifit we get in this option is we would support higher current for the RF block for all the use-cases and thermal dissipation of internal LDO is eliminated, this reduces thermal hot-spot within the device and gets distributed to the board.

I drew a small diagram to illustrate this mode of operation to understand better.

Thanks and regards,

CHETHAN KUMAR Y.B.

0 Tom Fisher over 4 years ago in reply to CHETHAN KUMAR Y.B.

Expert 1440 points

Hi CHETHAN KUMAR Y.B.,

Your explanation is really thorough, clear and helpful. Thanks a lot.

Cheers,

Tom

0 CHETHAN KUMAR Y.B. over 4 years ago in reply to Tom Fisher

TI__Mastermind 25825 points

Hello Tom,

Thanks for your kind words.

Thanks and best regards,

CHETHAN KUMAR Y.B.

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IWR6843: LDO BYPASS config