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AN66308 - CY8CMBR2044 CapSense® Design Guide, Doc. No. 001-66308 Rev. *F

Revision History

Document Revision History

Document Title: AN66308 - CY8CMBR2044 CapSense

Design Guide

Document Number: 001-66308

Revision

Issue Date

Origin of

Change

Description of Change

12/30/2010

ANBA

New Design Guide.

03/03/2011

ANBA

Multiple chapter enhancements for content and reader clarity.

06/01/2012

UDYG

Multiple chapter enhancements for content and reader clarity.

01/07/2013

SLAN

Added C

recommendations to PCB Layout Guidelines.

01/21/2016

VAIR

Added Glossary.

02/06/2017

SLAN

Updated to new template.

Completing Sunset Review.

07/04/2017

AESATP12

Updated logo and copyright.

Summary of Contents for CapSense CY8CMBR2044

Page 1: ...AN66308 CY8CMBR2044 CapSense Design Guide Doc No 001 66308 Rev F Cypress Semiconductor 198 Champion Court San Jose CA 95134 1709 Phone USA 800 858 1810 Phone Intnl 408 943 2600 http www cypress com...

Page 2: ...ANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE To the extent permitted by applicable law Cypress reserves the right to make changes to this document without further notice Cypress does not assume any...

Page 3: ...pSense Schematic Design 15 3 1 CY8CMBR2044 Configuration Options 15 3 1 1 CapSense Buttons CSx 15 3 1 2 General Purpose Outputs GPOx 15 3 1 3 Modulation Capacitor CMOD 15 3 1 4 Button Auto Reset ARST...

Page 4: ...Time TS 34 5 2 3 Average Current in NO TOUCH State IAVE_NT 35 5 2 4 Average Current in TOUCH State IAVE_T 35 5 2 5 Average Standalone Current IAVE_SA 35 5 2 6 Average Current IAVE 35 5 2 7 Average Po...

Page 5: ...and mechanical design considerations for the CY8CMBR2044 Low power design considerations for the CY8CMBR2044 Additional resources and support for designing CapSense into your system Cypress s CapSens...

Page 6: ...prototype 12 Test and evaluate system functionality and CapSense performance Meets specifications 13 Production Yes No Topics covered in this document 1 Understand CapSense technology 4 Mechanical Des...

Page 7: ...pSense capacitive touch sensing to your user interface This device uses hardware to perform system configuration eliminating the need for software tools firmware development and device programming The...

Page 8: ...ing even with closely spaced buttons Configurable LED ON Time after button release Button output reset if touched for excessive time User controlled Button Scan Rate Serial Debug Data output o Simplif...

Page 9: ...ence documentation Read about the sourcefile hex file in the PSoC Designer User Guide Bracketed Bold Displays keyboard commands in procedures Enter or Ctrl C File Open Represents menu paths File Open...

Page 10: ...sed in more detail in Capacitive Sensing Method Figure 2 1 CapSense Implementation in a CY8CMBR2044 Device CY8CMBR2044 CMOD Sensor Capacitors Each sensor input pin is connected to a sensor pad by trac...

Page 11: ...order of magnitude greater than CF CP usually ranges from 10 pF to 20 pF but in extreme cases it can be as high as 40 pF CF usually ranges from 0 1 pF to 0 4 pF Capacitive Sensing Method CY8CMBR2044...

Page 12: ...sensor scan and the accumulated result is a digital output value known as raw count which is directly proportional to CX This raw count is interpreted by high level algorithms to resolve the sensor s...

Page 13: ...cases a change in CP detunes the system resulting in unfavorable button performance either too sensitive or insensitive or even a nonoperational button In either situation you must retune the system...

Page 14: ...Review System Integration Retuning for any changes Tuning process Production Fine Tuning Design Validation Production Typical capacitive user interface Design Cycle Firmware Development Feasibility St...

Page 15: ...es a connection to one of the capacitive sense inputs You must ground all unused CapSense CSx inputs pins General Purpose Outputs GPOx There are four active LOW outputs on the CY8CMBR2044 controller G...

Page 16: ...r Auto Reset period Button is touched for more than the Auto Reset period After the GPOx is turned off because of Button Auto Reset feature and after the button is released do not touch the button for...

Page 17: ...by allowing only one CSx to be in the TOUCH state at a time If a finger contacts multiple CSx buttons only the first one to sense a TOUCH state will turn ON FSS also is useful when a button can produc...

Page 18: ...range from 0 ms to 2000 ms Figure 3 6 LED ON Timing CS0 GPO0 LED ON Time The LED ON Time duration D is configurable from the Delay pin For different values of resistors connected to the Delay pin the...

Page 19: ...e ON OFF is enabled LED ON Time applies only to one GPOx at a time meaning the LED ON Time counter resets every time a CSx transitions to a NO TOUCH state Figure 3 7 illustrates how LED ON Time operat...

Page 20: ...CMBR2044 Button shorting Button Shorted to VDD If any button is found to be shorted to VDD it is disabled Figure 3 9 Button Shorted to VDD CY8CMBR2044 Button shorting VDD Button to Button Short If two...

Page 21: ...ST and CS2 CS3 Failing 5ms pulse GPO3 GPO2 GPO1 High GPO0 High 5ms pulse Scan Rate Sleep Use this pin to set the button scan rate and sleep mode operation of the CY8CMBR2044 Do not leave this pin floa...

Page 22: ...apacitance for all buttons When Serial Debug Data is enabled this information is output on a single CSx pin To enable Serial Data Out pull down the CSx pin where you want the serial data to appear wit...

Page 23: ...ton status least significant bit LSB contains CS0 status 15 GPO_Status Gives GPO status LSB contains GPO0 status 16 0x00 17 CS1_Cp CS1 parasitic capacitance pF in Hex 18 CS0_Baseline_MSB Unsigned 16 b...

Page 24: ...F Table 3 6 Serial Debug Data Arranged in Multichart Raw Count Array Baseline Array Signal array MSB LSB MSB LSB MSB LSB 0 0x00 FW_Revision CS_Status GPO_Status 0x00 CS2_Cp 1 0x00 CS0_Cp 0x00 CS1_Cp 0...

Page 25: ...and feature settings and recommends whether the design is fit for mass production General Layout Guidelines The table below summarizes the layout guidelines for the CY8CMBR2044 These guidelines are d...

Page 26: ...elp you with button development Noise conditions can vary button to button based on the end system environment If the noise conditions are unknown use medium noise conditions as the starting point The...

Page 27: ...nRate Sleep pin Refer to Section 3 4 Scan Rate and Table 3 4 Table C outputs the button response time based on the inputs in Tables A and B Figure 3 14 CP Power Consumption and Response Time Calculato...

Page 28: ...csv To know more about MultiChart see AN2397 CapSense Data Viewing Tools 4 Click on Enable disable log file This will automatically store the data to the log file Log this data for at least 300 sampl...

Page 29: ...are outside of best design practices If the button board does not pass the Design Toolbox will provide recommendations There are four areas that can be changed to remedy a failing design button size t...

Page 30: ...d overlap D Overlay thickness To increase the CapSense signal strength choose an overlay material with a higher dielectric constant decrease the overlay thickness and increase the button diameter The...

Page 31: ...our system to maintain an appropriate distance between the CapSense controller and possible sources of ESD If it is not possible to maintain adequate distance place a protective layer of a high breakd...

Page 32: ...as conducted noise Examples include power and communication lines Because the CapSense controllers are low power devices you must avoid conducted emissions The following guidelines will help to reduc...

Page 33: ...wer consumption calculations described in the following sections The average power consumed by the CY8CBMR2044 is determined by calculating the parameters below 1 Button Scan rate TR 2 Scan time TS 3...

Page 34: ...Rate And the second is the time it takes to respond to any subsequent TOUCH after it wakes up 80 ms Scan Time TS Approximate scan time can be calculated using Equation 7 Where KCSX button sensitivity...

Page 35: ...rent in TOUCH State IAVE_T Equation 9 Where TS Scan time ISLEEP current consumed by CY8CMBR2044 during low power sleep mode from Table 5 2 IACTIVE current consumed by CY8CMBR2044 during active operati...

Page 36: ...TOUCH state is calculated as follows using Equation 14 and the maximum values for ISLEEP and IACTIVE Equation 14 The average current in TOUCH state is calculated as follows using Equation 15 Equation...

Page 37: ...de Scan all buttons with 20 ms Scan Rate Scan time Sleep time NO button touched for 2 secs Yes Scan all buttons with user defined scan rate Is any button active Yes No No Because low power sleep mode...

Page 38: ...sheet for the CapSense CY8CMBR2044 device is available at www cypress com CY8CMBR2044 Design Toolbox The interactive Design Toolbox will enable you to design a robust and reliable CY8CMBR2044 CapSense...

Page 39: ...n about advanced capacitive touch interface topics Cypress Developer Community Connect with the Cypress technical community and exchange information CapSense Product Selector Guide See the complete pr...

Page 40: ...Design Guide Doc No 001 66308 Rev F 40 7 Appendix Schematic Example Schematic 1 Four Buttons with Four GPOs In the above schematic the device is configured as CS0 CS3 pins 560 to CapSense buttons o F...

Page 41: ...nd o Modulator capacitor XRES pin Floating o For external reset Toggle FSS pin Ground o Toggle ON OFF disabled o FSS disabled ARST pin 5 k to Ground o Button Auto Reset enabled Auto Reset Period 20 se...

Page 42: ...s CS0 CS2 o CS3 not used in design GPO0 GPO2 pins LED and 560 to VDD GPO3 floating GPO0 GPO1 pins interfaced to Master o CapSense buttons driving three LEDs GPO0 GPO2 o GPO0 GPO1 interfaced to master...

Page 43: ...R11 Acronyms Acronym Description AC Alternating current ARST Auto Reset CF Finger capacitance CP Parasitic capacitance CS CapSense CSD CapSense Sigma Delta EMC Electromagnetic Compatibility ESD Elect...

Page 44: ...ween Raw Count and Baseline If the difference is negative or if it is below Noise Threshold the Difference Count is always set to zero Capacitive Sensor A conductor and substrate such as a copper butt...

Page 45: ...tate of the sensor Sensor state is reported ON if the Difference Count is higher than Finger Threshold Hysteresis and it is reported OFF if the Difference Count is below Finger Threshold Hysteresis Ga...

Page 46: ...ged in a specific linear fashion to detect the physical position in single axis of a finger Low Baseline Reset A parameter that represents the maximum number of scan samples where the Raw Count is abn...

Page 47: ...nmental changes Noise CapSense Noise The variation in the Raw Count when a sensor is in the OFF state no touch measured as peak to peak counts Noise Threshold A parameter used to differentiate signal...

Page 48: ...sensor from reporting the ON status for an indefinite period of time When Sensor Auto Reset is disabled the Baseline is updated only when the Difference Count is less than the Noise Threshold Sensor...

Page 49: ...parameters required for CapSense operation VREF Programmable reference voltage block available inside PSoC used for CapSense and ADC operation Widget A user interface element in the CapSense componen...

Page 50: ...Description of Change 12 30 2010 ANBA New Design Guide A 03 03 2011 ANBA Multiple chapter enhancements for content and reader clarity B 06 01 2012 UDYG Multiple chapter enhancements for content and r...

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