MSP430FR2111 Datasheet, PDF (61/75 Pages) Texas Instruments – Mixed-Signal Microcontrollers

www.ti.com
MSP430FR2111, MSP430FR2110
SLASE78A – AUGUST 2016 – REVISED AUGUST 2016
7.1.6 General Layout Recommendations
• Proper grounding and short traces for external crystal to reduce parasitic capacitance. See MSP430
32-kHz Crystal Oscillators for recommended layout guidelines.
• Proper bypass capacitors on DVCC, AVCC, and reference pins if used.
• Avoid routing any high-frequency signal close to an analog signal line. For example, keep digital
switching signals such as PWM or JTAG signals away from the oscillator circuit and ADC signals.
• See Circuit Board Layout Techniques for a detailed discussion of PCB layout considerations. This
document is written primarily about op amps, but the guidelines are generally applicable for all mixed-
signal applications.
• Proper ESD level protection should be considered to protect the device from unintended high-voltage
electrostatic discharge. See MSP430 System-Level ESD Considerations for guidelines.
7.1.7 Do's and Don'ts
During power up, power down, and device operation, the voltage difference between AVCC and DVCC
must not exceed the limits specified in the Absolute Maximum Ratings section. Exceeding the specified
limits may cause malfunction of the device including erroneous writes to RAM and FRAM.
7.2 Peripheral- and Interface-Specific Design Information
7.2.1 ADC Peripheral
7.2.1.1 Partial Schematic
Figure 7-5 shows the recommended decoupling circuit with either an internal or an external voltage
reference.
Using an external
positive reference
Using an external
negative reference
+
10 µF 100 nF
+
10 µF 100 nF
DVSS
VREF+/VEREF+
VEREF-
Figure 7-5. ADC Grounding and Noise Considerations
7.2.1.2 Design Requirements
As with any high-resolution ADC, appropriate printed-circuit-board layout and grounding techniques should
be followed to eliminate ground loops, unwanted parasitic effects, and noise.
Ground loops are formed when return current from the ADC flows through paths that are common with
other analog or digital circuitry. If care is not taken, this current can generate small unwanted offset
voltages that can add to or subtract from the reference or input voltages of the ADC. The general
guidelines in Section 7.1.1 combined with the connections shown in Section 7.2.1.1 prevent this.
In addition to grounding, ripple and noise spikes on the power-supply lines that are caused by digital
switching or switching power supplies can corrupt the conversion result. TI recommends a noise-free
design using separate analog and digital ground planes with a single-point connection to achieve high
accuracy.
Copyright © 2016, Texas Instruments Incorporated
Applications, Implementation, and Layout
61
Submit Documentation Feedback
Product Folder Links: MSP430FR2111 MSP430FR2110