AR1000_16 Datasheet, PDF (13/61 Pages) Microchip Technology – AR1000 Series Resistive Touch Screen Controller

AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
3.6 Status LED
The LED and associated resistor are optional.
FIGURE 3-5:
LED SCHEMATIC
The LED serves as a status indicator that the controller
is functioning. It will slow flash when the controller is
running with no touch in progress. It will flicker quickly
(mid-level on) when a touch is in progress.
If the LED is used with SPI communication, then the
LED will be off with no touch and flicker quickly
(mid-level on) when a touch is in progress.
Note:
If the SIQ pin is not used, it must be left as
a No Connect and NOT tied to circuit VDD or
VSS.
3.7 WAKE Pin
The AR1000’s WAKE pin is described as “Touch
Wake-Up/Touch Detection”. It serves the following
three roles in the controller’s functionality:
• Wake-up from touch
• Touch detection
• Measure sensor capacitance
The application circuit shows a 20 KΩ resistor
connected between the WAKE pin and the X- pin on the
controller chip. The resistor is required for product
operation, based on all three of the above roles.
3.8 ESD Considerations
ESD protection is shown on the 4-wire, 5-wire, and
8-wire interface applications schematics.
The capacitance of alternate ESD diodes may
adversely affect touch performance. A lower
capacitance is better. The PESD5V0S1BA parts shown
in the reference design have a typical capacitance of 35
pF. Test to ensure that selected ESD protection does
not degrade touch performance.
ESD protection is shown in the reference design, but
acceptable protection is dependent on your specific
application. Ensure your ESD solution meets your
design requirements.
3.9 Noise Considerations
Touch sensor filtering capacitors are included in the
reference design.
Warning: Changing the value of the capacitors may
adversely affect performance of the touch system.
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DS40001393C-page 13