Hi, I'm Melissa at Keysight Technologies
as today's design move more and more towards
battery-powered devices like smartphones,
tablets, and other handhelds, I thought it
would be useful to show how you can make
current consumption measurements on your
designs when looking for small current
signals. Here I've got my battery powered
device which in this case is a cellphone
and to make the current consumption
measurement I want to use this high
sensitivity current probe and high
signal integrity oscilloscope. The
probe I'm using today comes with a handful
of these make-before-break connectors.
You can see I already have one installed
in my circuit here. So i'm going to add
this make-before-break receptacle on to
those test points and this just lets me
easily connect to my probe tip. And what I
really love about these make-before-
break connectors is that if I have more
than one test point on my board that I
want to be looking at during testing,
I don't have to resolder my probe tip
connections anymore. I can just easily
disconnect from one make-before-break
connector and move to another. I also
have this ground connection here. I'm
going to connect that to the ground lug
on the probe. Now I'm going to power up
my device and as that powers up I'm
going to set up my oscilloscope. So I'm going to
turn on two grids and turn on channel 2
I'm going to move channel 2 into the
second grid here and I'm also going to
turn on roll mode so I'm going to go to
set up and acquisition. And what roll does,
is it turns off any triggering and it
just displays the data of the waveform
from right to left on the screen. So I've
got that turned on now
and the reason why I put up two grids
here for channel one and channel two is
because the probe I'm using has two
different amplifiers so that we can see
multiple views of the waveform. On
channel 2 here, this is the zoomed out
view. This is going to be the view that
I'll use to view the whole waveform at
once and to catch any large current
signals. For example if I were to press a
button on the phone or answer a phone
call I would see a larger current spike
here and that's what I use channel 2 for
zoomed out view. Then I have channel
1 which is the zoomed in view and this
will let us zoom in onto the signal to
see the small signal currents that might
be hidden when you have those large
signal packets when you're in the zoomed
out view.
we'd used this, for example, when my cell
phone is an idle mode it's only going to
be sending out very small current
packets to check in with the cell tower
or to wait for more information.
So let's go ahead and scale up these
waveforms. I'm going to go to one second
per division and on my zoomed-in view.
I'm going to go down to 20 milliamps per
division. I'm going to
pull this down so we can see the
whole waveform on screen here, maybe a
little further, and then on channel 2 I'm
going to go to about a hundred milliamps
per division. This red box here shows the
portion of the zoomed out waveform that
we're zooming in on up here. Now it looks like
we're in idle mode and we're getting a
small current packet about every second
so I'm going to go ahead and stop the
acquisition and I'm going to zoom in
on one of these packets
Alright, so now that I have one of these
packets on screen, I'm going to add my
current consumption measurement. So I go
to measure, add measurement, I'm going to
choose mixed and charge and that's on
channel one and i'm going to click ok.
Now we can see that on this signal we've
got about 27 nanoamp-hours and now
that we know how to make these
measurements we can characterize our
devices and we can make sure we're
meeting specification. The probe I'm
using in today's video is the N2820A
high sensitivity current probe and I'm
using that with the S-series oscilloscope.
If you enjoyed today's video
please like, share, and subscribe to the
Keysight Oscilloscope YouTube channel
and if there are any other topics that
you'd like us to discuss please leave
those in the comments below