Accelerate EMI qualification of automotive touchscreens with new capacitive touch controllers
July 01, 2019
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Key Facts:
- maXTouch® TD touchscreen controllers significantly increase signal-to-noise ratio
- Family supports touchscreens from nine- to 20-inch touchscreens with thick cover lenses
- Functional safety features designed to meet Automotive SPICE Level 3 capability and ASIL B
- EMI optimisation tool uses waveform shaping to save costly EMC test chamber time
The TD family of touch controllers features a new differential mutual signal acquisition method that significantly increases the Signal-to-Noise Ratio (SNR). This allows the use of very thick glass or plastic cover lenses and multi-finger thick gloved touch support up to the equivalent of 4.5 mm polymethyl methacrylate (PMMA).
The MXT1067TD, MXT1189TD and MXT1665TD devices add several variants that are cost-optimised for nine- to 13-inch automotive touchscreens to Microchip’s portfolio and are complemented by the recently introduced MXT449TD, MXT641TD, MXT2113TD and MXT2912TD devices supporting up to 20-inch touchscreens. Each device addresses aspects of the increasing demand for functional safety features and is designed in accordance with the Automotive SPICE Level 3 capability and ISO 26262 Automotive Safety Integrity Level (ASIL) B requirements.
All devices in the TD family feature a unique waveform shaping capability to optimise the performance of the touch controller’s radiated emissions through an EMI optimisation tool. Working with product experts in Microchip’s worldwide application design centres, this tool allows developers to enter user-defined RF limits and tune the shape of the transmitted burst waveform used for the touch-sensing acquisition.
Waveform shaping is achieved through firmware parameters derived from the tool and helps designers to position the fundamental burst frequency to work together with other in-vehicle applications, such as the remote keyless entry system. The resulting parameters are then simply added to the maXTouch configuration file, which customises the touch controller performance to the individual customer design.
The MXT1067TD, MXT1189TD and MXT1665TD devices add several variants that are cost-optimised for nine- to 13-inch automotive touchscreens to Microchip’s portfolio and are complemented by the recently introduced MXT449TD, MXT641TD, MXT2113TD and MXT2912TD devices supporting up to 20-inch touchscreens. Each device addresses aspects of the increasing demand for functional safety features and is designed in accordance with the Automotive SPICE Level 3 capability and ISO 26262 Automotive Safety Integrity Level (ASIL) B requirements.
All devices in the TD family feature a unique waveform shaping capability to optimise the performance of the touch controller’s radiated emissions through an EMI optimisation tool. Working with product experts in Microchip’s worldwide application design centres, this tool allows developers to enter user-defined RF limits and tune the shape of the transmitted burst waveform used for the touch-sensing acquisition.
Waveform shaping is achieved through firmware parameters derived from the tool and helps designers to position the fundamental burst frequency to work together with other in-vehicle applications, such as the remote keyless entry system. The resulting parameters are then simply added to the maXTouch configuration file, which customises the touch controller performance to the individual customer design.
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