NXP Semiconductors KE17Z User Manual

KE17ZDTSIUG
KE17Z Dual TSI User Guide
Rev. 0 - 05 May 2022

1 Introduction

Touch Sensing Interface (TSI) provides touch sensing detection on capacitive
touch sensors. The external capacitive touch sensor is typically formed on
PCB. The sensor electrodes are connected to TSI input channels through the
I/O pins in the device.

1.1 KE17Z dual TSI

KE17Z MCU has two TSI modules. It supports two kinds of touch
sensing methods: self-capacitance (also called self-cap) mode and mutual­
capacitance (also called mutual-cap) mode.
The dual-TSI technology of KE17Z MCU supports up to 50 touch channels. The
two TSI modules not only increase the number of touch electrode, but also work
in parallel to increase the scanning efficiency of touch electrode and save the
scanning time.
To enhance the liquid tolerance and improve the driving ability, each TSI
module has three shield channels, up to 25 touch channels for self-cap mode,
and up to 6 × 6 touch channels for mutual-cap mode. Both mentioned methods
can be combined on one single PCB, while only the lower 12 TSI channels
TSI[0:11] can be used for mutual mode.
TSI[0:5] are TSI TX pins and TSI[6:11] are TSI RX pins in
mutual mode.
• In the self-capacitive mode, developers can use these 50 channels to
design 50 (25 × 2) touch electrodes.
• In the mutual-capacitive mode, design options expand to up to 72 (6 × 6
× 2) touch electrodes.
In some use cases, such as, a multi-burner induction cooker with touch controls
or touch keyboards, the MCUs can support touchscreen designs scaling up
to 98 touch electrodes (26 electrodes using self-capacitance + 72 electrodes
using mutual channels).

1.2 TSI model comparison of KE17Z parts

Table 1 lists the number of TSI channels corresponding to different parts of
KE17Z. These parts all support dual TSI modules.
NOTE
Contents
1 Introduction......................................1
1.1 KE17Z dual TSI............................1
1.2 TSI model comparison of KE17Z
parts............................................. 1
1.3 TSI model comparison between
KE17Z parts and KE15Z parts..... 3
1.4 KE17Z dual TSI evaluation board
..................................................... 6
2 TSI self-cap mode introduction....... 7
2.1 Self-cap touch sensor.................. 7
2.2 Self-cap sensing mode................ 7
2.3 Clock generation.......................... 9
2.4 TSI scan time and scan result
accumulation..............................12
2.5 Scan time and sensitivity boost
tests in self-cap mode................ 15
3 TSI Mutual-cap mode.................... 18
3.1 Mutual-cap sensor..................... 18
3.2 Clock generation in mutual-cap
mode.......................................... 19
3.3 Mutual-cap sensing mode..........20
3.4 Sensitivity boost in mutual-cap
mode.......................................... 23
4 Shield channels............................. 24
4.1 Principle of self-cap mode to
improve liquid tolerance by
enabling shield channels........... 24
4.2 Advantages of three shield
channels of KE17Z of each TSI. 25
4.3 Principle of mutual-cap mode to
improve liquid tolerance............. 25
5 Hardware design guide................. 25
5.1 Electrode design........................ 26
5.2 PCB trace routing.......................26
5.3 Ground plane............................. 27
5.4 Overlay of the touch electrode... 28
5.5 Electrodes placement................ 30
5.6 Hardware checklist.....................30
5.7 X-KE17Z-TSI-EVB touch electrode
patterns design.......................... 30
6 References.................................... 34
7 Revision history............................. 34
Legal information.................................... 35
User Guide