Agilent U2531A User guide [de]

Agilent

U2531A USB Simultaneous Sampling DAQ in

Power Measurement Unit Monitoring

Application Note

Introduction

Mobile devices are getting more and
more popular. The mobile phone in
the market now has become a pocket
media center. It contains at least a
digital still camera, video conference
functionality, an MP3 player with
simulated surround sound, and a
color Internet browser coupled with
3-D gaming capability. Mobile phones
are continuously equipped with an
increasing number of functions, and
newer phones will come with higher
resolution cameras, adding various
kinds of storage attachment, mobile
television and personal security
devices such as thumbprint sensors.
Mobile phone power management
thus, becomes one of the most
signifi cant engineering challenges.
Other than mobile phones, the other
portable devices like handheld devices,
Personal Digital Assistants (PDAs),
Smart Phones, Portable Multimedia
Players (PMPs), MP3 players, Gaming,
and Global Positioning System (GPS)
also present increasingly sophisticated
functionality and application
requirements.

To achieve seamless playing of music, gaming, and voice and video call on
the mobile phones, it is necessary that the power outputs from the power
management unit remain stable. This will ensure a good customer experience
arising out of using the mobile devices.

For this reason, it is necessary to have a quick and easy design validation of
the power management unit by monitoring the stability of the power inputs and
outputs while switching between the functions of the PMU. The PMU typically
has an input and a few outputs. The parameters to be measured of each channel
will be both the voltage and current. In this particular application, the PMU
has an input and four output ports. Thus, if both voltage and current are to be
monitored for each port, then a total of ten measurement channels are needed.

PMU Monitoring

In the following sections, this application note focuses on how a PMU (in this
case a PMU with one input port and four output ports) can be monitored. The
purpose of this application is to monitor the channels to determine if the outputs
of the PMU are sending out stable signals when the different functions of the
PMU are executed during design validation. This can be seen easily by detecting
if spikes are present, as shown in Figure 1.

With increasing demands of
functionality and application
requirements, there will also be
an increasing power management
complexity of the overall system.
The drive for these portable device
manufacturers is then moving towards
a power management solution that
is lower in total system cost, and
is fl exible and scalable enough to
manage these demanding power
requirements. The power management
unit (PMU) would be expected to have
different voltage and current outputs
as well to interface to the different
functionality blocks. This voltage
range could range from millivolts to up
to 3.3 V. The current could be in the
range of milliamperes.

Figure 1. Graph indicated a transient signal detected.

To simulate an aging process and to run through all the functionality of the PMU,
the duration of the test will take several hours. Since both voltage and current
measurements need to be made for each port, the total number of channels
needed would be ten. In this particular test, three data acquisition (DAQ) devices
like the U2531A 2 MSa/s, 4-channel simultaneous sampling multifunction DAQ
device and the U2781A 6-Slot USB modular instrument chassis will be most
suitable. Since the maximum voltage output for this particular PMU is 3.3 V, it
can be connected directly to the input of the DAQ device. The current can be
easily measured by measuring the voltage across a resistor. The block diagram
in Figure 2 illustrates how this test is conducted.

Figure 2. Block diagram shows the test setup of PMU monitoring.

2