C™ Serial Interface ................................................................................................................................................................. 6
Packaging Information ............................................................................................................................................................. 34
Index ........................................................................................................... ........................................................................................ 42
The Microchip Web Site ....................................................................................................................................................................... 43
Customer Change Notification Service ................................................................................................................................................ 43
Customer Support ................................................................................................................................................................................ 43
Product Identification System .............................................................................................................................................................. 45
TO OUR VALUED CUSTOMERS
It is our intention to provide our valued customers with the best documentation possible to ensure successful use of your Microchip
products. To this end, we will continue to improve our publications to better suit your needs. Our publications will be refined and
enhanced as new volumes and updates are introduced.
If you have any questions or comments regarding this publication, please contact the Marketing Communications Department via
E-mail at
docerrors@microchip.com
or fax the
Reader Response Form
in the back of this data sheet to (480) 792-4150. We
welcome your feedback.
Most Current Data Sheet
To obtain the most up-to-date version of this data sheet, please register at our Worldwide Web site at:
http://www.microchip.com
You can determine the version of a data sheet by examining its literature number found on the bottom outside corner of any page.
The last character of the literature number is the version number, (e.g., DS30000A is version A of document DS30000).
Errata
An errata sheet, describing minor operational differences from the data sheet and recommended workarounds, may exist for current
devices. As device/documentation issues become known to us, we will publish an errata sheet. The errata will specify the revision
of silicon and revision of document to which it applies.
To determine if an errata sheet exists for a particular device, please check with one of the following:
• Microchip’s Worldwide Web site;
http://www.microchip.com
• Your local Microchip sales office (see last page)
When contacting a sales office, please specify which device, revision of silicon and data sheet (include literature number) you are
using.
Customer Notification System
Register on our web site at
www.microchip.com
to receive the most current information on all of our products.
DS41668A-page 2
Preliminary
2012 Microchip Technology Inc.
MTCH112
1.0
DEVICE OVERVIEW
1.5
1.5.1
Pin Description
MTI0/MTI1
The Microchip mTouch™ sensing MTCH112 Dual-
Channel Proximity/Touch Controller provides an easy
way to add proximity and/or touch sensor detection to
any application. The device implements either two
capacitive sensors or one sensor and one active guard
driver. The optional device configuration through I
2
C™
allows presets to be loaded in a production environ-
ment. Automatic calibration routines are used by
default to choose the best options, so user configura-
tion is not required.
The MTCH112 uses a sophisticated optimization
algorithm to actively eliminate noise from the signal.
While the noise level is being measured, the
requirements for a proximity or touch detection are
updated to reflect the degree of uncertainty in the
readings. When a press is detected for the first time,
the threshold is automatically calibrated to choose a
smart threshold for the ‘release’ and next press. This
creates a system that dynamically optimizes the signal-
to-noise ratio for its environment.
Connect the sensor to this input. An additional resistor
of at least 4.7 k
is recommended for best noise
immunity. Sensors up to 40 pF in capacitance are
supported. Sensors work best when the base
capacitance is minimized. This will maximize the
percentage change in capacitance when a finger is
added to the circuit.
1.5.2
MTGRD0
When not scanning the pin for capacitance changes
(MTI1 functionality), the pin will be driven in phase with
MTI0 to minimize the voltage differential between the
two pins. If the MTGRD0 pin’s trace surrounds the
MTI0 pin’s trace, the waveform on MTGRD0 will shield
(or guard) MTI0 from the effect of nearby noise sources
or power planes.
1.5.3
MTO
1.1
Automatic Calibration
It measures the amount of capacitance on each sensor
pin and chooses the best of three possible waveforms
to capture a capacitive measurement.
It analyzes the two final settling voltages of the MTI0
pin to more closely match the waveform on the
MTGRD0 pin.
The settling time for the waveform is calibrated to
maximize sensitivity while minimizing the delay. This
provides the best trade-off between signal and noise
reduction.
Calibration results are stored in the on-board EEPROM
for faster recovery time on next power-up. These
memory locations are accessible for read/write through
the I
2
C communications to bypass the automatic
calibration, if required.
The mTouch™ sensing output pin is always driven to
either V
DD
or V
SS
by the device. The MTCH112
OUTCON register (see
Register 3-1)
determines the
behavior of the MTO/INT pin. The pin is always active-
low, but the states in which this output occurs can be
adjusted in the device’s OUTCON register. If no options
are selected for output states, the MTO pin acts as an
interrupt to a master device. The MTCH112 will pulse
low for at least 1 ms if any state changes occur. Further
information must be determined by communicating
through I
2
C with the device.
1.5.4
I
2
C – SERIAL DATA PIN (SDA)
1.2
Communications
• I
2
C, Slave mode
1.3
Touch Configurations
The SDA pin is the serial data pin of the I
2
C interface.
The SDA pin is used to write or read the registers and
Configuration bits. The SDA pin is an open-drain
N-channel driver. Therefore, it needs an external pull-
up resistor from the V
DD
line to the SDA pin. The rec-
ommended resistance value is 1.5 k. Except for Start
and Stop conditions, the data on the SDA pin must be
stable during the high period of the clock. The high or
low state of the SDA pin can only change when the
clock signal on the SCL pin is low. Refer to
Section 2.1.2 “I2C Operation”
for more details on I
2
C
Serial Interface communication.
• MTI0 is a dedicated capacitive sensor input
• MTI1/MTGRD0 can either be another capacitive
sensor or a guard driver for MTI0
1.4
• 13 bits
Signal Resolution
2012 Microchip Technology Inc.
Preliminary
DS41668A-page 3
MTCH112
1.5.5
I
2
C – SERIAL CLOCK PIN (SCL)
1.6.3
HARDWARE
The SCL pin is the serial clock pin of the I
2
C interface.
The I
2
C interface only acts as a slave and the SCL pin
accepts only external serial clocks. The input data from
the master device is shifted into the SDA pin on the
rising edges of the SCL clock, and output from the
device occurs at the falling edges of the SCL clock. The
SCL pin is an open-drain N-channel driver. Therefore,
it needs an external pull-up resistor from the V
DD
line to
the SCL pin. The recommended resistance value is
1.5 k. Refer to
Section 2.1.2 “I2C Operation”
for
more details on I
2
C Serial Interface communication.
For more details, see
Figure 1
and
Table 1.
Capacitive sensors are areas of metal connected
through a series resistor of 4.7 kΩ to one of the MTIx
pins. The following diagrams show some example
layout configurations along with the recommended
design guidelines. For more information about the
design of capacitive sensors, see AN1334,
“Techniques
for Robust Touch Sensing Design”.
FIGURE 1-1:
TWO-SENSOR LAYOUTS
— EXAMPLE
Single Layer PCB, Two Sensors
(1)
(2)
1.6
1.6.1
Performance
(3)
PROXIMITY DISTANCE
The maximum proximity distance will be highly
dependent on the level of noise in the environment. To
maximize the robustness of the controller, the noise
level is measured and used to define how much shift is
required in the signal before a reliable change in state
can be determined. These values were taken in a low-
noise environment. For more details, see
Figure 4-2.
MTIN1
MTIN0
NOTE:
1:
2:
3:
15 mm x 15 mm recommended.
Maximize separation distance.
Thickness of traces to pin: 0.1 – 0.5 mm
1.6.2
RESPONSE TIME
The response time is defined as the maximum amount
of time delay between the sensor’s capacitance signif-
icantly changing and the output being updated based
on the OUTCON register’s configuration.
This amount of time will be dependent on the LPCON
register, as it determines how long the device will sleep
after detecting no significant changes. The fastest
response time can be achieved by setting the LPCON
register for the minimum Sleep time (see
Register 3-6).
The controller only sleeps when idle and no changes in
the environment are detected. If a change occurs, the
device will operate without sleeping until the
disturbance or capacitance is removed. For more
details, see
Table 4-2.
Two Layer PCB, Two Sensors
(1)
(2)
MTIN1
MTIN0
NOTE:
1:
2:
3:
15 mm x 15 mm recommended.
Maximize separation distance.
Thickness of traces to pin: 0.1 – 0.5 mm
DS41668A-page 4
Preliminary
2012 Microchip Technology Inc.
Ground Plane or
Noise Source
(3)
Ground Plane or
Noise Source
MTCH112
FIGURE 1-2:
GUARD LAYOUTS —
EXAMPLE
Layout for Single Layer PCBs
(1)
(2) (3)
(4)
MTIN0
Layout for Thin PCBs
Front View
MTGRD0
(4)
(1)
(2) (3)
MTIN0
MTGRD0
Back View
MTIN0
Layout for Reverse-side Shielding
(Min. PCB layer separation of 1.5mm is recommended.)
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
