LAUNCHXL-CC2650: CC2650

Hi Oleg,

When you connect to the SensorTag are you using the same external 1.8V power supply or are you using a battery?

Hello,

In addition, how do you have the VSENSE jumper configured on the CC2650 LaunchPad? A photo would be helpful. Have you also completed the check items on the "CC2640 HW Troubleshooting & Bring Up" article on the TI BLE Wiki?

Best wishes

Hi Oleg,

In this case you should not provide 1.8 V to the LaunchPad, but to your board. You must also remove the Vsense jumper. For details see the "external debug target" section at the bottom of this page: dev.ti.com/.../

As JXS wrote, a picture would be helpful!

Cheers,
Fredrik

hello, thanks for your responce, I attach the picture of debug connection

Hi Oleg,

This looks correctly set up, except for it does not look like you are supplying voltage to your target board. Is it powered? 

Cheers,
Fredrik

Yes, our target board have own power supply = 1.8V. And debugger have own supply too = 1.8V.
We has resolved this issue. We did JTAG lines shorter then was before, and their length approximately ~15 centimeter at this moment.
So, I think the problem was in long JTAG cable.
Thanks all.

Hi Oleg,

That is good to hear. Long JTAG cables is a common problem :-)

Cheers,
Fredrik

15cm is about 6 inch. That is still pretty long. If you search for TI JTAG guideline then you will find information tell you that buffers should be added if the cable length is too long. Personally, I always keep JTAG cable shorter than 10cm.

Btw, I would like to suggest you not to use 1.8V power supply. I would use a higher voltage, say 2.0V~2.2V, in case any ripple occurs in the power rails. The ripple is very easily to be observed when RF is activated. Since RF is activated as short pulses, you will observe corresponding ripples on 1.8V. If this happen then CC2640 might get reset or the memory/register values are no longer maintained. In any case, your program will be out of control and it is very difficult to debug.

Hi Robert,

When configured for "External Regulator mode" it is perfectly fine to run off 1.8 V. It is actually recommended. From Oleg's first post it seems he has configured the device correctly for this operation.

Regards,
Fredrik

Yes, theoretically.

For external regulator mode, VDDS and VDDR are connected on PCB. The normal operation range is 1.7V ~ 1.95V, and the maximum rating is 2.25V.

I don't know what is the power source of the 1.8V in Oleg's "custom reference board". But the power source and the bulk capacitors are very important for stable and long time operation. If the power source is from a coin-cell battery then the internal resistance will increase as time goes by. If the bulk capacitors are not placed well at the final (production) PCB then large ripples will occur on VDDS rails when RF is activated.

So, this is why I suggest to use a higher voltage than 1.8V. I think 2V should be okay even it is a little higher than 1.95V. If you don't feel comfortable with 2V, then 1.95V should be used. In any case, don't exceed 2.25V, the maximum rating.

If the power source is very stable from time to time and has very little drift within wide temperature range, then it is okay to use 1.8V. In this case, the bulk capacitors should be still well placed.

Hi Robert,

Please do not argue further on this topic. The information you are providing is not accurate, and may confuse other people. External Regulator Mode is specifically designed to run off 1.8 V power supplies. We have characterized this mode to ensure proper operation, and there are several such designs in mass production. The reference design should of course be followed: 

 SimpleLink CC2650 EVM Kit 4XS_Ext_Reg (CC2650EM-4XS_Ext_Reg) v2.0.0 Design Files

 Using the Wireless SimpleLink CC26xx in Ext Regulator Mode With the TPS62740

Robert Chen said:

The normal operation range is 1.7V ~ 1.95V, and the maximum rating is 2.25V.

2.25 V is the Absolute Maximum limit. This does not mean operation up to this voltage is recommended. The supply voltage should never increase the recommended operating range in normal usage. For Ext. Reg. the operating range is up to 1.9 V.

Robert Chen said:

But the power source and the bulk capacitors are very important for stable and long time operation. If the power source is from a coin-cell battery then the internal resistance will increase as time goes by. If the bulk capacitors are not placed well at the final (production) PCB then large ripples will occur on VDDS rails when RF is activated.

That is correct, as with any design using the CC2640. External regulator mode is designed to run off regulated power rails. There are no common batteries available, including coin cells that will support this voltage range anyway.

Robert Chen said:

So, this is why I suggest to use a higher voltage than 1.8V. I think 2V should be okay even it is a little higher than 1.95V. If you don't feel comfortable with 2V, then 1.95V should be used. In any case, don't exceed 2.25V, the maximum rating.

Voltage above 1.95 V should not be used. Anyway, running off 1.8 V is not a concern.

Robert Chen said:

If the power source is very stable from time to time and has very little drift within wide temperature range, then it is okay to use 1.8V. In this case, the bulk capacitors should be still well placed.

This is true for most LDOs and DCDCs. 

Regards,
Fredrik

Not to argue, just to share some experiences. I apologize if I was wrong.