SLAA842B December   2018  – August 2019 DS90C401 , DS90C402 , MSP430FR2512 , MSP430FR2522 , MSP430FR2532 , MSP430FR2533 , MSP430FR2632 , MSP430FR2633 , MSP430FR2672 , MSP430FR2673 , MSP430FR2675 , MSP430FR2676

 

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5.2 Device Selection

TI offers a wide range of programmable CapTIvate microcontrollers. Use the requirements defined in Step 2 to select the best CapTIvate device for the application.

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Table 6 summarizes the number sensors and detection supported by the CapTIvate MCUs. Table 7 and Table 8 compare the two generations of CapTIvate technologies. Table 9 lists the CapTIvate key parameter performance under different test condition.

Table 6. CapTIvate Family Devices

CapTIvate Pins (RX or TX)
4 Pins 8 Pins 16 Pins
Parallel CapTIvate Measurement Blocks 1 MSP430FR2515IRHL MSP430FR2512IPW16 Devices in this row measure one electrode at a time
2 MSP430FR2522IRHL MSP430FR2522IPW16 Devices in this row can measure up to two electrodes in parallel for faster scanning in applications with many electrodes
4 MSP430FR2633IYQW MSP430FR2632IYQW MSP430FR2632IRGE MSP430FR2532IRGE MSP430FR2633IRHB MSP430FR2633IDA MSP430FR2533IRHB MSP430FR2533IDA MSP430FR2676TPT MSP430FR2676TRHA MSP430FR2676TRHB MSP430FR2675TPT MSP430FR2675TRHA MSP430FR2675TRHB Devices in this row can measure up to four electrodes in parallel for the fastest scanning in applications with many electrodes
Devices in this column have 4 CapTIvate pins and support up to 4 electrodes Devices in this column have 8 CapTIvate pins and support up to 8 electrodes in self-capacitance mode or 16 electrodes in mutual-capacitance mode Devices in this column have 16 CapTIvate pins and support up to 16 electrodes in self-capacitance mode or 64 electrodes in mutual-capacitance mode

Table 7. Device Generations

First-generation devices MSP430FR2512, MSP430FR2522, MSP430FR2632, MSP430FR2633, MSP430FR2532, MSP430FR2533
Second-generation devices MSP430FR2675, MSP430FR2676
Device-dependent features FRAM, RAM, capacitive-touch I/Os, sensing blocks, package, power consumption, other peripherals

Table 8. Comparison of First-Generation and Second-Generation Device Features

Generation-Dependent Feature First-Generation Devices Second-Generation Devices Advantages of Second Generation Over First Generation
Sensing modes Self capacitance and mutual capacitance Self capacitance and mutual capacitance  —
Electrode charge voltage VREG mode (1.5 V) VREG mode (1.5 V)
DVCC mode (2.7 V to 3.6 V)		 Improved SNR and conductive noise immunity with DVCC mode
Total electrode capacitance 300 pF at 4-MHz conversion frequency 300 pF at 4-MHz conversion frequency  —
Input bias current No Yes Improved conductive noise immunity
Conversion processing
(noise filter, drift compensation, detection, event timing)		 Hardware state machine Hardware state machine  —
Noise immunity processing
(frequency hopping, oversampling)		 Software Hardware state machine CPU no longer required for frequency hopping and oversampling

Table 9. CapTIvate Key Parameter Performance Under Different Test Conditions

Parameter Description Test Condition 1st Generation 2nd Generation
Proximity Detection Range Proximity sensors are electrodes designed to detect a hand or other conductive object at some distance using greater sensitivity compared to buttons. Proximity sensor design involves carefully balancing sensor size, sensor configuration, ground shielding and system stability.
  • The test PCB has a proximity sensor of 80 mm by 50 mm with 10-mm wide rectangular ring shape with centered hatched GND.
  • Simulated outstretched finger approaching the sensor.
 Typical: 25 mm Typical: 70 mm
  • The test PCB has a proximity sensor of 80 mm by 50 mm with 10-mm wide rectangular ring shape with centered hatched GND.
  • Simulated flat hand approaching the sensor.
 Typical: 75 mm Typical: 110 mm
Sensor Electrode Size The sensitivity of a sensor can depend on a variety of parameters, but those parameters that have the greatest impact are the overlay material, overlay thickness and type of electrode and electrode size. It is critical to balance the electrode size to achieve desired sensitivity and reliable touch performance.
  • The test PCB is a 2 layer design with approximately 25% hatched GND on top and bottom layers with 4-mm plastic overlay
 Minimum Recom­mended: 64 mm2 Minimum Recom­mended: 36 mm2
  • The test PCB is a 2 layer design with approximately 25% hatched GND on Top and Bottom layers with 4-mm glass overlay
 Minimum Recom­mended: 50 mm2 Minimum Recom­mended: 36 mm2
Response Time Response time is defined as the time between a finger touchdown event on the sensor electrode and the touch controller generating an response signal. This parameter is particularly important because it directly translates to how fast users can interact with the touch panel. More signal processing provides a more reliable system but the trade-off is longer response time.
  • The test PCB has 16 self mode buttons, conversion frequency 2 MHz and conversion count set to 500. Gen1: MSP430FR2633, Gen2 MSP430FR2676
  • Frequency hopping and oversampling not enabled.
Typical: 4 ms Typical: 4 ms
  • The test PCB has 16 self mode buttons, conversion frequency 2 MHz and conversion count set to 500. Gen1: MSP430FR2633, Gen2 MSP430FR2676
  • Frequency hopping enabled.
Typical: 14 ms Typical: 10 ms
  • The test PCB has 16 self mode buttons, conversion frequency 2 MHz and conversion count set to 500. Gen1: MSP430FR2633, Gen2 MSP430FR2676
  • Frequency hopping and 2x oversampling enabled.
Typical: 26 ms Typical: 15 ms
Noise Immunity Capacitive touch sensing involves the measurement of very small changes in capacitance so the system that are going to be used in noisy environments must be designed with noise immunity in mind from the start. Capacitance electrodes become more sensitive to touch when the system is subjected to conducted noise. This error in touch sensitivity could lead to false touch when the user gets close to the button but does not actually touch the button.
  • CAPTIVATE-EMC EVM was used for this test. A simulated human finger was placed 5 mm above the sensor electrode during the test.
  • 3 Vrms conducted noise coupled directly into DC power supply, noise frequency was swept from 300 kHz to 80 MHz
 PASS with No False Touch
(Requires additional software algorithm)(1)(2) 		PASS with No False Touch
(No additional software algorithm required)(1)(3)
  • CAPTIVATE-EMC EVM was used for this test. A simulated human finger was placed 5 mm above the sensor electrode during the test.
  • 10 Vrms conducted noise coupled directly into DC power supply, noise frequency was swept from 300 kHz to 80 MHz
 PASS with No False Touch
(Requires additional software algorithm)(1)(4) 		PASS with No False Touch
(No additional software algorithm required)(1)(5)
(1) The error in touch sensitivity is defined as conversion result over touch threshold when noise is present.
(2) Maximum error in touch sensitivity: self mode: 46.2%, mutual mode: 13%
(3) Maximum error in touch sensitivity: self mode: 7.7%, mutual mode: 4.3%
(4) Maximum error in touch sensitivity: self mode: 150%, mutual mode: 45.5%
(5) Maximum error in touch sensitivity: self mode: 46.2%, mutual mode: 21.7%