From: Bdale Garbee Date: Mon, 14 Nov 2011 09:20:34 +0000 (-0700) Subject: fix a couple typos and formatting errors X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=commitdiff_plain;h=d36bb15af8d10da2e3dbb6c3f603bce22a900d80 fix a couple typos and formatting errors --- diff --git a/bdale/blog/posts/RF_Immunity.mdwn b/bdale/blog/posts/RF_Immunity.mdwn index ff7fe70..c6c7f0b 100644 --- a/bdale/blog/posts/RF_Immunity.mdwn +++ b/bdale/blog/posts/RF_Immunity.mdwn @@ -7,7 +7,7 @@ every case, these problems have been completely resolved by either making sure the system battery has sufficient charge before launch, or through the application of standard engineering techniques such as twisting wire pairs to reduce differential coupling. However, even when every technique we could -think of had been applied, once in a while someone still has issues. +think of had been applied, once in a while someone still had issues. Around the time of LDRS this year, the incidence of such reports seemed to increase. One customer, in particular, had an installation in which he @@ -69,9 +69,9 @@ to reproduce the problem reliably on a test board at my bench! On further analysis, we realized that the output of the USB battery charger chip and the input of the LDO both expect a 1uF bypass cap to ground. At -some point, those looked redundant and we eliminated one of the two. -Unfortunately, we weren't internalizing the fact that the switch leads were -between the two caps, and the one we left was on the output of the charger +some point, those looked redundant and we eliminated one of the +two. Unfortunately, we weren't internalizing the fact that the switch leads +were between the two caps, and the one we left was on the output of the charger and not at the input of the LDO. Placing a suitable bypass cap right at the input of the LDO turns out to have a truly dramatic effect on RF immunity! @@ -79,7 +79,7 @@ Once we realized that RF getting into the LDO input was the problem, Keith pointed out that we used to see "noise" in the accelerometer data on earlier boards that was caused by the 3.3 volt rail moving slightly during radio transmit, which we fixed with a hardware change on v1.1. We are now -convinced that this was at least party related to RF coupling to the LDO +convinced that this was at least partly related to RF coupling to the LDO input, not just the change in power consumption on the LDO output. We didn't realize what was going on in earlier testing because we often didn't have ematches wired up, so RF coupling was minimal. But going back to