What ground should I connect TPS71501 PGND or AGND ??

marcelo deoliveira

Other Parts Discussed in Thread: MSP430F2013, BQ24650, TPS715

I am designing with TPS71501 that powers a MSP430F2013. The circuit board also has BQ24650 which requires PGND and AGND.

My question is , which one of this ground do I connect the MSP430 and for the TPS71501 ??

Thanks

over 13 years ago

0 Bill Stokes over 13 years ago

TI__Expert 8890 points

Hi Marcelo,

The PGND is typically understood as a local "split" ground to the power supply where local high di/dt, noise currents can be somewhat isolated from other sensitive applications. The AGND is used as reference plane for the compensation and feedback circuitry in order to assure an accurate, noise free output voltage. Ultimately, however, both grounds will be connected together somewhere, of course. Your MSP430, since it is a digital device, will be mostly immune to the noise/current issues. Usually there is a common ground plane to which everything is connected including PGND and AGND. Please consult the MSP430 applications group for best grounding practices for their parts.

Bill

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

Hi Bill

Thanks for your help.

My issue is that because BQ24650 requires 2 ground which are been connected togueter under the termal pad, I am not sure wich ground to tigh the MSP and LDO TPS. I looked over the MSP430 group and did not find anything related to it.

Thanks

0 Bill Stokes over 13 years ago in reply to marcelo deoliveira

TI__Expert 8890 points

Hi Marcelo,

Attach the MSP430 ground to the PGND point nearest to the output capacitor of its power source.

Bill

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

Hi Bill

What about the LED TPS71501 ? This is the one that is confusing the most ...

Marcelo

0 Bill Stokes over 13 years ago in reply to marcelo deoliveira

TI__Expert 8890 points

Marcelo,

The output capacitor of the TPS715 should also be connected to PGND too. Let me back up, sorry for the confusion. PGND is referred to in various ways. Local PGND is to contain noisy stuff from the switching regulator. But then there is extended PGND that goes to all the other parts that are powered by the power sources. The TPS715 will be associated with PGND.

Bill

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

Thanks

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

Hi Bill

For some reason I don't think the last post went correct. Please see the attached to a copy of it.

Thanks

0 Bill Stokes over 13 years ago in reply to marcelo deoliveira

TI__Expert 8890 points

All seems good.

Thanks.

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

Bill

Do you see the pictures ? I need to know what ground to connect where , PGNG and AGND.

Thanks

0 Bill Stokes over 13 years ago in reply to marcelo deoliveira

TI__Expert 8890 points

Marcelo,

Nope, I see no pictures. Can you attach them as a file?

0 marcelo deoliveira over 13 years ago in reply to Bill Stokes

Intellectual 840 points

3704.Question.doc

Please see if you got now .

Thanks

0 marcelo deoliveira over 13 years ago in reply to marcelo deoliveira

Intellectual 840 points

Bill

Please see the page 17 on the sluu444a to understando what I am talking about the grounds ...

Thanks

0 Bill Stokes over 13 years ago in reply to marcelo deoliveira

TI__Expert 8890 points

Hi Marcelo,

Assuming that the TPS715 supplies the 2.8V power to the MSP430 then all those grounds (marked by "?" (?GND)) should be connected together. If the BQ output (VOUT) is connected to +SYSTEM LOAD then the BQ's PGND should be connected to the ?GND.

I am going home early for the weekend.

Regards

Bill

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What ground should I connect TPS71501 PGND or AGND ??