TWR-K60N512-KEIL Freescale Semiconductor, TWR-K60N512-KEIL Datasheet - Page 158

• Manufacturer Part Number: TWR-K60N512-KEIL
• Description: K60N512 Keil Tower Kit
• Manufacturer: Freescale Semiconductor
• Series: Kinetisr
• Type: MCUr

Specifications of TWR-K60N512-KEIL

• Rohs Compliant: YES
• Contents: 4 Boards, Documentation, DVD
• Peak Reflow Compatible (260 C): Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: Freescale Tower System, K60N512

Introduction
Figure 17-1. Capacitive touch sensing electrode model
A common measurement method for capacitive touch sensing is the RC method. In this
method a large pullup resistor (approximately 1 MΩ) is connected to each electrode. The
processor or sensing ASIC measures the time it takes the electrode (or capacitor) to
become charged, when a finger approaches the electrode, the capacitance increases and
so does the charging time, this charge time change is considered a touch. The problem
with this method is the pullup. It is a weak pullup, and thus susceptible to external noise.
The TSI uses a different measurement method. It has two constant current sources, one
for charging and the other for discharging the electrode. This creates a triangular wave.
This wave has a configurable peak to peak voltage or delta voltage. Observe
Figure
17-2.
It shows the electrode current source oscillator structure.
Figure 17-2. TSI Electrode current source oscillator
Kinetis Quick Reference User Guide, Rev. 0, 11/2010
158
Freescale Semiconductor