AWR1843： How to use the internal LDO

Jun Suzuki

Part Number: AWR1843

Hi Experts,

I am considering using the internal LDO of the AWR1843.
I have listed the following related questions, please answer.

(1) When using an internal LDO, does the LDO supply power to VIN_13RF2, VIN_13RF1, VOUT_PA?
　Or is it just VOUT_PA?

(2) Currently, it is set to use LDO for evaluation. (VIN_13RF2 = VIN_13RF1 = 1.3V)
　Originally, VOUT_PA should be unconnected (open), but now it is connected to 1.3V.
　This is because VOUT_PA and 1.3V are connected in a board pattern and cannot be unconnected.
　Is it okay to use it in this way?

(3) Even in the state of (2), it looks like it is working normally. Please tell me why it does not malfunction.

Best regards,

Jun

over 4 years ago

0 Cesar over 4 years ago

TI__Guru*** 149084 points

Please give us some time to review this question

thank you

Cesar

0 aozer over 4 years ago

TI__Mastermind 30715 points

Hello,

You should only use the internal LDO if you are supplying 1.3V. If you supply 1.0V, you need to bypass the LDO.

1. There are two internal LDOs. One takes the 1.3V supply and brings it down to 1.0V for the internal RF blocks, the VOUT_PA has a separate internal LDO which is output on the VOUT_PA pin and supplies the power amplifier.

2.VOUT_PA has a separate internal LDO, when using 3TX simultaneously this LDO cannot supply enough power so you need to connect to the external 1.0V supply and disable the VOUT_PA LDO.

3. Connecting VOUT_PA to the external 1.3V is not recommended. VOUT_PA has it's own internal LDO, you are now connecting the output of this internal LDO to the 1.3V supply on the board. It may not damage immediately, but may cause issues over time. If you are connecting VOUT_PA to an external supply, this supply should be 1.0V and you should disable the internal VOUT_PA LDO.

You can find more details about the usage if you search on the forums, i.e.

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/814493/awr1243-4-awr1243-cascade-evm-vout_pa-shorted-by-default-to-ar_1v0_rf2

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/766238/awr1642-awr1642-vout_pa-output

Regards,

Adrian

0 Jun Suzuki over 4 years ago in reply to aozer

Prodigy 30 points

Hello,
Thank you for your quick response.
I have additional questions.

(1) For two internal LDO , is it necessary to set the LDO (enable / disable) separately for RF and VOUT_PA?

(2) 1V is supplied to the terminal of RF / VOUT_PA.
And if LDO is enabled, will that setting be ignored? Or will the LDO be enabled?
Is there any problem with this usage?

Best regards,
JUN

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AWR1843： How to use the internal LDO