I get the following problem with the tocuh controller ADS7843, when use capacitores for noise filter on X+,Y+,X-,Y- inputs. If the capacitores are present we can not move the cursor properly. Because mismatch exist between the pen and the cursor on the touch panel.
The funcion used for calibrate is tc_calibrate and the funcion used for test is ts_test my system is linux 22.214.171.124 and ts.lib 1.0. The circuit is the same that appears in the application note "Touch Screen Controller Tips" http://focus.ti.com/docs/prod/folders/print/ads7843.html
If i take the capacitores and the TVS all work fine, but i need protect that input.
It sounds like it could be a few different possibilities. Would you mind providing the schematics around the ADC? Also, the capacitor values, if you don't mind. Many thanks and we look forward to assisting you with this.
Tanks for reply i attach the schematics, the capacitor value is .01uF and the TVS have 56pf .
Thanks for the schematic. Does the problem arise only when C162/V42 through C165/V45 are installed or is it all transorbs? Can you perhaps get some oscilloscope screen shots of the SCLK, SDI, SDO and /CS input as well?
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.