TLV8544: TLV8544: a signal pulse from the output when send message via bluetooth.

Khieu Sy

Part Number: TLV8544

Hi TI experts,

I am designing pir circuit with bluetooth low energy. I use TLV8544 to amplify the signal from the pir and bluetooth ic will receive the signal for processing.

it is my schematic for my project.

and Bluetooth chip, i use TLSR253 from telink semiconductor.

I'm having a very complicated problem and I've been trying to fix it for a week now and it didn't work.

whenever I send my message board via bluetooth I get a signal pulse from the output of the 2nd amplifier floor ( TP10 ). The PIR block works perfectly when i don't send any message boards via bluetooth.

I'm using boost converter +3V3 TLV61224DCKR for the Vin.

I tried removing the boost converter to use battery power directly for the circuit but the problem still didn't get solved.
Even though I used two different sources to supply the module, of course I grounded the two sources, I still received the signal pulse from TP10.

This is a signal from TP10 when I sent a message board from Bluetooth (I created a dark room to cover the sensor).

Where can this cause come from?

Thank you.

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Khieu,

I would shield the analog circuit. Put the analog circuit into a metallic enclosure and connect it to signal ground. Have a small hole for the measuring window of PIR.

Even a piece of aluminium foil or copper foil can help.

Kai

0 Khieu Sy over 4 years ago in reply to kai klaas69

Prodigy 50 points

Hi Kai,

Thanks for your suggestions. I couldn't do that with my plan because of the mechanic.

I tried a simple test and I found something interesting.

I found oscillations between two lands of two blocks. Perhaps this is the reason why the reference on the pir module is wrong.

Do you have any idea about this?

Khieu Sy

0 kai klaas69 over 4 years ago in reply to Khieu Sy

Guru 140200 points

Hi Khieu,

what is the pink curve and what is the yellow curve?

Kai

0 Ron Michallick over 4 years ago in reply to kai klaas69

TI__Guru*** 140136 points

Khieu Sy,

Trace routing and bluetooth antenna placement is very important to minimise coupling. If coupling can't be reduced then you may have to ignore PIR (go blind) for a short time when transmitting.

0 Khieu Sy over 4 years ago in reply to kai klaas69

Prodigy 50 points

Hi Kai,

Yellow is a pir signal, purple eyebrow is the deviation between two earths of two blocks after isolation.

Khieu Sy

0 Khieu Sy over 4 years ago in reply to Ron Michallick

Prodigy 50 points

Hi Ronald,

thanks for the suggestions, the pir noise is up to 1.5 seconds, this will really make it difficult for the user experience. I will try your suggestion with the software process.

Khieu Sy

0 kai klaas69 over 3 years ago in reply to Khieu Sy

Guru 140200 points

Hi Khieu,

I would try to shield the analog circuit. This can help a lot. Take a copper foil which is isolated on the back side to prevent short circuits. And don't forget to connect the copper foil to signal ground.

The use of a printed circuit board containing a solid ground plane can also help a lot. In mixed analog digital circuits I do always use a solid ground plane. Also, I strictly separate the analog and digital sections from each other.

Kai

0 Khieu Sy over 3 years ago in reply to kai klaas69

Prodigy 50 points

Hi kai,

i will try that, thank for your help.

Khieu Sy

0 kai klaas69 over 3 years ago in reply to Khieu Sy

Guru 140200 points

You are welcome :-)

Good luck!

Kai

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TLV8544: TLV8544: a signal pulse from the output when send message via bluetooth.