ORIGINAL: Kinky John Fowler
ORIGINAL: Moerig
RF Noise from sources like electric motors and static buildup.
From the Device Datasheet:
Datasheet Document #: 38-16015 Rev. *I on page 23 refers to L/D pin recommendation changed to :
''PMU inductor/diode connection, when used. If not used, connect to GND.
From Cypress technical support:
If the L/D pin is left floating, the switching regulator inside the PMU will pick up noise which will in turn increase the radio noise and the noise on the board.
PMU refers to Power Management Unit. It is a feature to prevent brownouts. Spektrum did not implement this feature and this pin was left unconnected.
This is a cut and dried technical issue confirmed by die chip vendor. Not debatable, sorry
Increase the radio noise and noise on the board - How much? 1/100000 above normal levels or enough to actually be a problem? Is this actually a serious problem or a recommendation? What is Spektrums response to this?
<br type=''_moz'' />
I dont think Spektrum is aware of this because it is a cheap fix. It is serious enough to have warranted an update to the effect from the original documentation after designers encountered this issue. All known commercial designs using this chip I came across have addressed this issue. The effect can range from 0dB to 12dB in RX sensitivity. 3dB halves range. Unless you are an expert in ISM RF comms that have knowledge to the contrary from the chip vendor there is no point in trying to dilute this clear design issue.
I am sure the Spektrum response if any will be that it is not an issue. I am sure customers having lost models will disagree.
BTW this document update was published April 2, 2007. Good engineering practice and ISO certifications require design revisions where issues are revealed. Spektrum may just have an old datasheet and did not keep up to date with the errata that all products reveal after field use.
As I see it they either are aware of the issue, not aware of it, or dont think its an issue.