Core engineering and protocols for Interposer Capacitance Detection.
Attaching any physical probe, wire, or interposer board inevitably adds parasitic capacitance and alters the transmission line impedance of the PCB trace. TPMShield incorporates high-precision analog sensing circuits into its I/O pads that measure trace capacitance down to 0.1 picofarads.
During power-on reset, TPMShield executes a microsecond Time-Domain Reflectometry (TDR) pulse check along the SPI bus traces. If the measured trace characteristics deviate from the factory-calibrated baseline profile, the chip flags an interposer presence, locks its secure NVRAM, and refuses to negotiate bus session keys.