Hardware
2.2.1
Measure MSP430 Current Draw
A specific jumper J9 is placed on the LaunchPad to allow for measuring current draw of the
MSP430FR5969 device. The current measured includes the FR5969, and any current drawn through the
BoosterPack headers and jumper J1.
To measure ultra-low power, follow these steps:
1. Remove the J9 jumper; attach an ammeter across this jumper.
2. Consider the effect that the backchannel UART and any circuitry attached to the FR5969 may have on
current draw. Maybe these should be disconnected at the isolation jumper block, or their current
sinking and sourcing capability at least considered in the final measurement.
3. Make sure there are no floating input I/Os. These cause unnecessary extra current draw. Every I/O
should either be driven out or, if an input, should be pulled or driven to a high or low level.
4. Begin target FR5969 execution.
5. Measure the current. (Keep in mind that if the current levels are fluctuating, it may be difficult to get a
stable measurement. It is easier to measure quiescent states.)
2.2.2
Clocking
The FR5969 LaunchPad provides external clocks in addition to the internal clocks in the device.
•
Y4: a 32-kHz crystal
•
Y1: an unpopulated region that supports HF crystal or resonator (4 to 24 MHz)
The 32-kHz crystal allows for lower LPM3 sleep currents than do the other low-frequency clock sources.
Therefore, the presence of the crystal allows the full range of low-power modes to be used.
For more information about internal clocks and how to use the 32-kHz or HF crystal, see the
MSP430FR59xx family user's guide
.
8
MSP430FR5969 LaunchPad™ Development Kit (MSP
‑
EXP430FR5969)
SLAU535B – February 2014 – Revised July 2015
Copyright © 2014–2015, Texas Instruments Incorporated
