7. Advanced Energy Monitor
7.1 Introduction
Any embedded developer seeking to make their embedded code spend as little energy as the underlying architecture supports needs
tools to easily and quickly discover inefficiencies in the running application. This is what the Simplicity Energy Profiler is designed to do.
In real-time, the Energy Profiler will graph and log current as a function of time while correlating this to the actual target application code
running on the EFR32. There are multiple features in the profiler software that allow for easy analysis, such as markers and statistics on
selected regions of the current graph or aggregate energy usage by different parts of the application. The Energy Profiler is available
through Simplicity Studio.
7.2 Code Correlation
By using the Energy Profiler, current consumption and voltage can be measured and linked to the actual code running on the EFR32 in
realtime. The Energy Profiler gets its data from the board controller on the mainboard through the Advanced Energy Monitor (AEM).
The current signal is combined with the target processor's Program Counter (PC) sampling by utilizing a feature of the ARM CoreSight
debug architecture, and the Instrumentation Trace Macrocell (ITM) block can be programmed to sample the MCU's PC at periodic inter-
vals and output these over SWO pin ARM devices. When these two data streams are fused and correlated with the running applica-
tion's memory map, an accurate statistical profile can be built that shows the energy profile of the running application in real-time.
7.3 AEM Circuit
The AEM circuit on the Wireless Pro Kit Mainboard (BRD4002A) and the Wireless STK Mainboard (BRD4001A) measures the current
through a sense resistor inside the feedback loop of a low-dropout regulator (LDO). The output voltage of this LDO powers the EFR32
when the power slide switch is in the AEM position. AEM usage on both mainboards is similar, but the implementation and perfomance
on the Wireless Pro Kit Mainboard (BRD4002A) has some key differences including the utilization of two sense resistors instead of one
and a different LDO, which is explained in Section
. The AEM implementation on the Wireless Pro Kit Mainboard
(BRD4002A) is shown in the figure below.
Power Select
Switch
VMCU
Sense Resistors
Current Sense
Amplifier
Multiple Gain
Stages
G
0
G
1
AEM
Processing
LDO
EFR32
Peripherals
0.5 Ω
5 V
10 Ω
High
Range
Calibrate
Figure 7.1. Advanced Energy Monitor On The Wireless Pro Kit Mainboard (BRD4002A)
Note:
The VMCU regulator feedback point is after the sense resistor to ensure that the VMCU voltage is kept constant when the output
current changes. Series resistances in the current path will, however, cause some IR drop on VMCU.
Note:
The AEM circuit only works when the kit is powered and the power switch is in the AEM position.
UG525: EFR32xG24 2.4 GHz 10 dBm Wireless Pro Kit User's Guide
Advanced Energy Monitor
silabs.com
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