Hi. My name is Bob Zollo of Agilent Technologies. Today I’m going to demonstrate how to test
a DC to DC converter in a better way using a new Agilent product. So the device under
test here that I’ll be demonstrating is this DC to DC converter. This is a 2.5 volt
input, 3 volt output, DC to DC converter. Now, typically when you would test a DC to
DC converter, you’d need a whole pile of instruments. You’d need a power supply to
source into the DC to DC converter. You’d need an electronic load on the output of the
DC to DC converter. You’d need an oscilloscope. You’d need a volt meter. You’d need some
current shunts in order to measure current. Well, all of that equipment is replaced by
the DC Power Analyzer and the modules that are installed inside it, so now you have a
single integrated package which allows for much faster setup and much easier testing.
So this is the N6705B DC Power Analyzer. We have it configured with two modules. It’s a
modular system. Module one is an SMU module, the N6781 SMU, and module two is also an
N6781 SMU. The first module, module one, is going to be powering the input of the device under test,
and the second module will be loading down the output of the device under test.
And what we’re going to be doing is a DC to DC startup test. So I have a block diagram
of the system here. In the block diagram you can see SMU number one is set to 2.5 volts
constant voltage, and that’ll be powering the DUT, the DC to DC converter, and SMU number two
will be on the output of the DC to DC converter. It’ll be set to draw 1 amp at
3.2 volts. So we’re able to source and load the DC to DC converter. Now, the test that
we’re actually going to be doing is a turn-on time test, so we’re going to turn on the
input side of the DC to DC converter and measure how long it takes for the power to come out
of the DC to DC converter. And of course that startup time is a critical measurement for
anyone who’s doing DC to DC converter design because the faster it starts up, the more
efficient it can be in its operation. I’m also going to be using some software to drive
this instrument. The software is called the 14585A software, and that is used to use the
large computer screen here to take care of the testing. So let me begin by bringing up
that software. And as you can see, it looks a lot like a scope trace. We are in oscilloscope mode.
And you will see the traces of voltage and current appear on the screen in a few
moments. Now, the first thing I’m going to do, I’ve preset everything. I’m going
to turn on output number two, which begins drawing current out of the device under test.
But since there’s no power being applied to it, it’s just a load sitting on the output.
Now, the next thing I’m going to do is I’m going to arm the oscilloscope by pressing
the scope button here, and now the scope is armed. When I push the on button on channel one,
that will apply power to the device under test, and that will also trigger the scope
to make a measurement. So let me go ahead and turn that on and you can see here now
there are some scope traces. So let me describe what’s on the screen here. So the DC Power Analyzer,
channel one, this trace is the voltage. And at T0, the voltage goes from 0 volts to
2.5 volts, so that’s the power being applied to the device under test. The second trace
here is the current being pulled out of channel one. And you can see here at the time when
the DC to DC converter power is applied, the current begins ramping up until the output
is turned on. Now, this is a unique capability of the DC Power Analyzer, the fact that it
can measure current directly via scope trace. Normally you would need a current shunt in
order to measure current with an oscilloscope, but that measurement is built directly into
the module, hence simplifying the test setup. Now, the green is channel two. That’s the
output side, and what you’ll see here is this is the voltage on the output. And when
the converter finally comes on, you’ll see the voltage jump up to 3.2 volts. So the turn on
test that we’re going to conduct is to measure the difference between this point
and this point in order to measure how long it takes for the output to come on. Now, I
could do that the old style way by counting the grids. It’s about three boxes, and it’s
set to ten milliseconds per division, so that’s about 30 milliseconds. But like an oscilloscope,
we have markers, so let’s bring up the markers and make the measurement with the markers.
So I have to turn this on. This brings up markers. Now I’ll put marker number one
on channel one where the power is supplied. I’ll put marker number two on channel two
where the output finally comes up. And if I go right to here, I can read off of that
28.8 milliseconds, which is the startup time on this DC to DC converter. So as you can see,
this measurement was very easy to do. It was just a simple matter of putting the
markers on the traces, and all of that trace information came out of a single box called
the DC Power Analyzer. Thank you.