AWR1843AOP: distance between the de-cap and the AOP PIN

mingyu OH

Part Number: AWR1843AOP

Tool/software:

Hello,

I would like to inquire about the distance between the de-cap and the AOP pins

During the PCB layout process using the AWR1843AOP chip, due to space constraints, the decoupling capacitors (DECAPs) for pins E1 and J1 were placed at distances of 5.6mm and 9mm, respectively (please refer to the attached photo).

We are aware that it is recommended to place decoupling capacitors as close to the pins as possible; however, due to physical limitations, we were unable to do so.

I would like to request your review on the following points:

1.Please confirm whether the current distances between the DECAPs and the pins (5.6mm and 9mm) could cause any issues with electrical stability.

2.If there is a recommended maximum allowable distance between the DECAP and the pin according to TI (Texas Instruments) guidelines, I would appreciate it if you could share this information.

I look forward to your response.

Thank you

3 months ago

0 Kundan Somala 3 months ago

TI__Expert 3760 points

Hi Mingyu, Thanks for reaching out over E2E.

Could you please confirm the end application that is being targeted for your product?

0 mingyu OH 3 months ago in reply to Kundan Somala

Prodigy 70 points

HI,

Thank you for answering

It is used as a short-range obstacle collision avoidance radar within 5 meters.
Also, we use the radar only in TDM (Time Division Multiplexing) mode.

0 Kundan Somala 3 months ago in reply to mingyu OH

TI__Expert 3760 points

Hi Mingyu,

It is recommended to have these caps as close as possible to the device with minimum loop length. Having a higher loop length could potentially cause EMI issues.

Thanks,
Kundan

0 mingyu OH 3 months ago in reply to Kundan Somala

Prodigy 70 points

Hi Kundan

Although I know that the de-cap should be placed as close as possible, there are significant space constraints in the design. Designing it as shown in the picture above is the best we can do.

If there is no specific recommendation regarding the maximum distance for the capacitor (CAP), is it acceptable to proceed with our design and use it as long as there are no issues in the EMI test?

Thanks,

Mingyu

0 Kundan Somala 3 months ago in reply to mingyu OH

TI__Expert 3760 points

Hi Mingyu,

There is a risk that you are carrying with the loop area formed as per the layout image shared. The 1.2V and 1.8V supplies are primary sources for 1.2GHz, 1.6GHz and 2.4GHz spurious emissions where the EMI limits are very stringent. Use 0201 or 0402 caps if space is the constraint in the layout.

Thanks,
Kundan

0 mingyu OH 3 months ago in reply to Kundan Somala

Prodigy 70 points

Hi Kundan

Additionally, is there any problem with arranging the DECAPs in the order of CAP - POWER - AOP as shown in the figure below?

Please check if it is okay not to arrange them in the order of POWER -> Capacitor -> AOP.

Thanks,

Mingyu

+1 Kundan Somala 3 months ago in reply to mingyu OH

TI__Expert 3760 points

Should be Ok.

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AWR1843AOP: distance between the de-cap and the AOP PIN