El escenario
An automotive diagnostic interface needs to connect a 3.3V microcontroller to the 12V K-line bus using the L9637 transceiver, with proper pull-up and supply filtering.
Qué hay en este dibujo
Lee las decisiones que hay detrás.
01
Use L9637 as the K-line transceiver with VS tied to vehicle battery for bus sensing
02
Power both transceiver and MCU from the 3.3V regulated rail for direct logic-level compatibility
03
Include a 1k pull-up on K-line to battery voltage and a 100pF filter capacitor for EMI suppression
Reuse this diagram as a template for any ISO 9141/ISO 14230 K-line interface where an L9637 or similar transceiver connects a 3.3V MCU to a 12V vehicle bus.