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TD1208R and TD1508 (US) SMPS instead of LDO

Posted: Fri Sep 09, 2016 9:33 am
by mikepokeeffe
Hi,

I'm currently designing a product that I want to work in both Europe and in the US (just by swapping a few components, TD1508 device and antenna matching circuit).

I'm swapping between using a battery at 3.6V (small voltage drop across diode gives 3.5V, keeping under maximum rating) and an external switching power supply.
I assume it's alright to use 3.5V input instead of the standard 3.0V or 3.3V?

I just want to confirm that using the recommended circuit in the TD1508 datasheet (Section 11.1) will be alright for the TD1208R as well??
The TD1208R only mentions using a bead.

Thanks in advance
Mike O'Keeffe

Re: TD1208R and TD1508 (US) SMPS instead of LDO

Posted: Thu Oct 20, 2016 3:07 pm
by mstempin
Yes, the recommendations given for the TD1508 also apply to other modules, it is just that the TD1508 being more demanding and being the last released module, this information is more detailed.

I would recommend to insert an linear voltage regulator with high PSRR after the SMPS, as the RF module is very sensitive to noise on the power line, and doing so will help you pass the certification tests.