3: Open-Q 845 µSOM Development Kit
Open-Q 845 µSOM Development Kit User Guide
21
Figure 5. SOM Current Sense Header J301 (5)
The table below summarizes the pin outs of header J301
Table 6 - Power Header J301 Pinout
Pin No
Signal
Description
1
SOM_PWR_SENSE_P
SOM power positive current sense line
2
SOM_PWR_SENSE_N
SOM power negative current sense line
3
GND
System Ground
To obtain power consumption measurements, the header is connected to a data acquisition unit
(Keithley 2701 or similar) and the voltages on the SOM_PWR_SENSE_P/N pins are captured a few times
a second over the test period (typically 30 minutes). The SOM power consumption is then calculated as
(where Rsense = 5 milliohms):
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
=
𝑉𝑉𝑃𝑃𝑃𝑃𝑃𝑃
𝑝𝑝𝑝𝑝𝑟𝑟
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑁𝑁
∗
(
𝑉𝑉𝑃𝑃𝑃𝑃𝑃𝑃
𝑝𝑝𝑝𝑝𝑟𝑟
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑃𝑃
− 𝑉𝑉𝑃𝑃𝑃𝑃𝑃𝑃
𝑝𝑝𝑝𝑝𝑟𝑟
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑁𝑁
)
𝑅𝑅𝑃𝑃𝑅𝑅𝑅𝑅𝑃𝑃𝑅𝑅
Use averaging to reduce noise.
