Hardware
11
SLAU772A – June 2018 – Revised March 2020
Copyright © 2018–2020, Texas Instruments Incorporated
MSP430G2553 LaunchPad™ Development Kit (MSP
‑
EXP430G2ET)
2.3.1
eZ-FET USB Power
The most common power-supply scenario is from USB through the eZ-FET debugger. This provides 5-V
power from the USB and also regulates this power rail to 3.3 V for eZ-FET operation and 3.3 V to the
target side of the LaunchPad development kit. Power from the eZ-FET is controlled by jumper J101. For
3.3 V, make sure that a jumper is connected across the J101 3V3 terminal.
2.3.2
BoosterPack Plug-in Module and External Power Supply
Header J4 is present on the board to supply external power directly. It is important to comply with the
MCU voltage operation specifications when supplying external power. The MSP430G2553 has an
operating range of 1.8 V to 3.6 V. For more information, see the
MSP430G2x53, MSP430G2x13 Mixed-
Signal Microcontrollers data sheet
2.4
Measure MSP430 Current Draw
To measure the current draw of the MSP430G2553 using a multi-meter, use the 3V3 jumper on the J101
jumper isolation block. The current measured includes the target MCU and any current drawn through the
BoosterPack plug-in module headers.
To measure ultra-low power, follow these steps:
1. Remove the 3V3 jumper in the J101 isolation block, and attach an ammeter across this jumper.
2. Consider the effect that the backchannel UART and any circuitry attached to the MSP430G2553 may
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.
3. Make sure there are no floating inputs/outputs (I/Os) on the MSP430G2553. 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.
4. Begin target execution.
5. Measure the current. 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.
2.5
Clocking
The MSP-EXP430G2ET provides an external clock in addition to the internal clocks in the MCU.
•
Y1: 32.768-kHz 12.5-pF crystal
The 32.768-kHz crystal allows for lower LPM 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.
By default, the crystal is not connected to the MSP430G2553 because the target pins are multiplexed with
two BoosterPack plug-in module header pins. 0-
Ω
resistors R3 and R9 must be removed, while R5 and
R7 must be shorted across to connect the external crystal to the MSP430G2553. See the onboard crystal
selection resistors silkscreen for how to configure the resistors to select between the crystal or the
BoosterPack plug-in module pins.
The internal clocks in the MCU default to the following configuration:
•
MCLK: DCO at 1 MHz
•
SMCLK: DCO at 1 MHz
•
ACLK: LFXT1 at 32.768 kHz
For more information about configuring internal clocks and using the external oscillators, see the
MSP430x2xx Family User's Guide
2.6
Using the eZ-FET Debug Probe With a Different Target
The eZ-FET debug probe on the LaunchPad development kit can interface to most MSP430 MCUs, not
just the onboard MSP430G2553 target MCU.
