Datasheet

MSP430FR4133, MSP430FR4132, MSP430FR4131

SLAS865B –OCTOBER 2014–REVISED AUGUST 2015

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Figure 7-5 shows the recommended decoupling circuit when an external voltage reference is used. The

internal reference module has a maximum drive current as described in the sections ADC Pin Enable and

1.2-V Reference Settings of the MSP430FR4xx and MSP430FR2xx Family User's Guide (SLAU445).

The reference voltage must be a stable voltage for accurate measurements. The capacitor values that are

selected in the general guidelines filter out the high- and low-frequency ripple before the reference voltage

enters the device. In this case, the 10-μF capacitor is used to buffer the reference pin and filter any low-

frequency ripple. A bypass capacitor of 100 nF is used to filter out any high-frequency noise.

7.2.1.3 Layout Guidelines

Components that are shown in the partial schematic (see Figure 7-5) should be placed as close as

possible to the respective device pins to avoid long traces, because they add additional parasitic

capacitance, inductance, and resistance on the signal.

Avoid routing analog input signals close to a high-frequency pin (for example, a high-frequency PWM),

because the high-frequency switching can be coupled into the analog signal.

7.2.2 LCD_E Peripheral

7.2.2.1 Partial Schematic

Required LCD connections greatly vary by the type of display that is used (static or multiplexed), whether

external or internal biasing is used, and also whether the on-chip charge pump is employed. For any

display used, LCD_E has configurable segment (Sx) or common (COMx) signals connected to the MCU

which allows optimal PCB layout and for the design of the application software.

Because LCD connections are application specific, it is difficult to provide a single one-fits-all schematic.

However, for an example of connecting a 4-mux LCD with 27 segment lines that has a total of 4 × 27 =

108 individually addressable LCD segments to an MSP430FR4133, see the MSP-EXP430FR4133

LaunchPad™ development kit (MSP-EXP430FR4133) as a reference.

7.2.2.2 Design Requirements

Due to the flexibility of the LCD_E peripheral module to accommodate various segment-based LCDs,

selecting the right display for the application in combination with determining specific design requirements

is often an iterative process. There can be well-defined requirements in terms of how many individually

addressable LCD segments must be controlled, what the requirements for LCD contrast are, which device

pins are available for LCD use and which are required by other application functions, and what the power

budget is, to name just a few. TI strongly recommends reviewing the LCD_E peripheral module chapter in

the MSP430FR4xx and MSP430FR2xx Family User's Guide (SLAU445) during the initial design

requirements and decision process. Table 7-1 provides a brief overview over different choices that can be

made and their impact.

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Product Folder Links: MSP430FR4133 MSP430FR4132 MSP430FR4131