We would like to test the “Carrier frequency offset” of the FINAL PRODUCT (which is “hermetically sealed” & no pins are available for the DTM UART 2-wire interface) during production - How do we d that ?

[Per Hillersborg]

Hi

We would like to test the “Carrier frequency offset” of the PCBA during production.
Like the BT SIG test: RFPHY/TRM/BV-06-C [Carrier frequency offset and drift, uncoded data at 1 Ms/s], using DTM.
Or something similar, using a CW.
No problem – very easy.

But we would also like to test the “Carrier frequency offset” of the FINAL PRODUCT during production.
Like the BT SIG test: RFPHY/TRM/BV-06-C [Carrier frequency offset and drift, uncoded data at 1 Ms/s], using DTM.
Or something similar, using a CW.

But now we have a problem, as our product is “hermetically sealed” & no pins are available for the DTM UART 2-wire interface.
Do you have any suggestions how to do that test ?

BR Per

[Håkon Alseth]

Hi,

 

Have you considered testing the devices prior to wielding the product?

Ie. do DTM on PCB level, and when sealed; do a final-test on a application level.

 

Kind regards,

Håkon

[Per Hillersborg]

Hi Håkon

Yes we do Carrier Offset DTM on PCB level (before the UltraSonic Welding (USW)). But we would like to re-test the Carrier Offset after USW, as it can harm the 32.xxx kHz XTAL (& 32 MHz XTAL).

BR Per

[Håkon Alseth]

Hi Per,

 

If you do a final-test on a application level, you will find out if there is a problem with the clock sources.

Note that DTM does not use the 32k, while the bluetooth stack itself uses both 32M (for radio, and radio related timers) and 32k (for time-keeping).

If one of these clock sources has failed due to welding, and you initiate any on-air bluetooth operation(s), you will be able to detect this instantly in the form of not picking up any advertising packets and/or showing connection problems.

 

Kind regards,

Håkon