Hardware
11
SLAU802 – March 2019
Copyright © 2019, Texas Instruments Incorporated
MSP430FR2476 LaunchPad™ Development Kit (LP
‑
MSP430FR2476)
2.3.2
CR2032 Battery Power
A CR2032 battery holder is on the back of the LP-MSP430FR2476 board to power the LaunchPad
development kit from a single coin battery. To power the LaunchPad kit from the CR2032 coin cell, insert
the battery securely and in the correct orientation, and remove all of the shunt jumpers from J101 except
the 3V3 jumper. Place the 3V3 jumper in the lower configuration to connect the battery output to the target
side 3.3-V rail. This placement is also shown on the silkscreen on the PCB. Place a shunt jumper across
J10. Alternatively, place an ammeter across the pins of J10 to measure current out of the battery.
Do not use the eZ-FET emulation circuit when the LP-MSP430FR2476 is powered from the CR2032 coin
cell battery. Remove all of the shunt jumpers on J101 except the 3V3 (which is in the lower position) to
disconnect the eZ-FET circuit from the target side of the LaunchPad development kit. The CR2032 voltage
level will decrease with use and can cause voltage level violations on the eZ-FET portion of the design if
left connected. To debug the target device, the LaunchPad development kit should be configured for eZ-
FET USB Power as shown in
When not using the CR2032 battery to power the board, be sure the 3V3 shunt jumper on J101 is not
placed in the battery configuration. It is also useful to remove the jumper from J10 to disconnect the
battery from the rest of the power domains. This ensures there is no risk of applying an external voltage
source to the battery.
2.3.3
BoosterPack Plug-in Module and External Power Supply
Headers J6 is present on the board to supply external power directly. It is important to comply with the
device voltage operation specifications when supplying external power. The MSP430FR2476 has an
operating range of 1.8 V to 3.6 V. More information can be found in the
2.4
Measure Current Draw of the MSP430 MCU
To measure the current draw of the MSP430FR2476 MCU using a multimeter, use the 3V3 jumper on the
J101 jumper isolation block. The current measured includes the target device and any current drawn
through the BoosterPack plug-in module headers.
To measure ultra-low power, follow these steps:
•
Remove the 3V3 jumper in the J101 isolation block, and attach an ammeter across this jumper. Be
sure to use the correct pair of pins as outlined in
to select between eZ-FET power and
CR2032 power.
•
Consider the effect that the backchannel UART and any circuitry attached to the MSP430FR2476 can
have on current draw. Consider disconnecting these at the isolation jumper block, or at least consider
their current sinking and sourcing capability in the final measurement.
•
If using the CR2032 to supply power, remove all shunt jumpers at J101, except 3V3 in the lower
position, and connect J10 with a shunt jumper.
•
Make sure there are no floating inputs/outputs (I/Os) on the MSP430FR2476. These cause
unnecessary extra current draw. Every I/O should either be driven out or, if it is an input, should be
pulled or driven to a high or low level.
•
Begin target execution.
•
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.
EnergyTrace technology can also be used to compare various current profiles and better optimize your
energy performance.
