MPR084Q Freescale Semiconductor, MPR084Q Datasheet - Page 10

• Manufacturer Part Number: MPR084Q
• Description: IC CTLR TOUCH SENSOR PROX 16-QFN
• Manufacturer: Freescale Semiconductor
• Type: Capacitiver

Specifications of MPR084Q

• Number Of Inputs/keys: 8 Key
• Data Interface: I²C, Serial
• Voltage - Supply: 1.8 V ~ 3.6 V
• Current - Supply: 1.62mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QFN Exposed Pad
• Output Type: Voltage
• Interface: I²C
• Input Type: Logic
• Supply Voltage: 3.3 V
• Dimensions: 5 mm L x 5 mm W x 1 mm H
• Supply Current: 41µA
• Ic Interface Type: I2C
• Supply Voltage Range: 1.8V To 3.6V
• Sensor Case Style: QFN
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +85°C
• Filter Terminals: SMD
• Rohs Compliant: Yes
• For Use With: KITMPR084EVM - KIT EVAL 8-PAD TOUCH MPR084
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MPR084
10
3
3.1
When using a capacitive touch sensor system the raw data must be filtered and interpreted. This process can be done many
different ways but the method used in the MPR084 is explained in this chapter.
3.2
The touch pad interface has to distinguish touch status through varying user conditions (different finger sizes in bare hands or
gloves) and environmental conditions (electrical and RF noise, sensor contamination with dirt or moisture).
The touch pad circuitry reports touch status as one of the following two conditions:
The touch pad is only touched in one position, ideally near the middle of one of the eight pads. If a touch occurs between pads,
untouched will be reported.
3.3
Since it is unlikely that in a real world case a single independent touch will occur two specific multi-touch response cases are
outlined. Methods for changing the sensitivity of the device will be discussed in another Chapter, but the important part is that the
sensitivity is determined by the strength of an input signal. If more than one input signal is above the selected sensitivity then the
touch sensor controller interprets this in a specific way. This functionality is broken down into two different cases.
3.3.1
Any time multiple touches are detected at the same time the touch sensor controller recognizes this case and accounts for it. The
number of allowed reported touches is settable using the Maximum Number of Touched Positions Register
case where this register is set to 1, all touches past the first will be ignored and unreported.
A special case is when exact 2 keys are involved in the interaction. In most cases one of the two electrodes will receive a stronger
signal than the other. If the difference in capacitance is statistically significant between the pad with the stronger signal will be
reported
This functionality is sometimes called 1-Keyed Lockout. by changing the Maximum Number of Touched Positions Register
(Section
3.3.2
Another case is when one touch pad is touched and held and a second touch pad is then touched and held. For this situation the
second touch will be ignored and the first touch will continue to be reported.
If the second touch is released before the first touch then the second touch will be completely ignored. But, if the first touch is
released before the second then the system will report that the first key is released and that the second key is now touched. This
functionality is sometimes called 2-Key Rollover.
3.4
The Touch Pad Configuration Register configures a variety of the MPR084 features. Each of these features is described in
following sections. The I
1.
2.
3.6). this value can be set. Thus the n-key lockout is determined by this register.
Touch Detection
Introduction
Understanding the Basics
Touch Pad untouched
Touch Pad touched on one of eight pads.
Conditional Output Scenarios
Simultaneous Touches
Sequential Touches
Touch Pad Configuration Register
Reset:
W
R
2
C slave address of the Touch Pad Configuration Register is 0x03.
TPSE
1
7
= Unimplemented
Figure 14. Touch Pad Configuration Register
6
0
0
BKA
5
0
ACE
4
0
TPRBE
3
0
TPTBE
2
0
1
0
0
Freescale Semiconductor
(Section
TPE
0
1
3.6). In the
Sensors