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fix a couple typos and formatting errors
author
Bdale Garbee
<bdale@gag.com>
Mon, 14 Nov 2011 09:20:34 +0000
(
02:20
-0700)
committer
Bdale Garbee
<bdale@gag.com>
Mon, 14 Nov 2011 09:20:34 +0000
(
02:20
-0700)
bdale/blog/posts/RF_Immunity.mdwn
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diff --git
a/bdale/blog/posts/RF_Immunity.mdwn
b/bdale/blog/posts/RF_Immunity.mdwn
index ff7fe704ab1d3256cf06fcafda9b3b99a8626f57..c6c7f0bb582d21c45518050cd6bf8d932ec44446 100644
(file)
--- 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
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 ha
s
issues.
+think of had been applied, once in a while someone still ha
d
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
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
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!
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
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 part
l
y 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
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