Keysight Technologies USB data capturing module 2531A Input: 1 MS/s, output: 1 MS/s U2531A OPT 902 + ABD Manuel D’Utilisation

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.

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. 

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. 

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.

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 1. Graph indicated a transient signal detected.

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