I3C Low-Voltage Buffer

The I3C SDA and SCL pads are equipped with fast low-voltage buffers that, when used in conjunction with the Multi-Voltage I/O (MVIO), can operate at up to 12.5 MHz at a voltage level as low as 1V.

Important: The I3C Low-Voltage Buffer is auto-enabled when VDDIOxLVEN = 0 and the VDDIOx voltage drops below 1.62V if the bandgap reference is already enabled. Refer to section Standard GPIO Buffers as I3C Pads for more information.

To use these buffers, the VDDIOxLVEN bit must be set in the I/O Low-Voltage Control (IOLVCON) register for the appropriate voltage domain.(1) Additionally, all the I2C/SMBus buffers must be disabled through the Threshold TH bits in the corresponding RxyI2C register.(2) Refer to the “I2C Pad Control” section in the “I/O Ports” chapter.

  1. 1.The I3C Low-Voltage Buffers can only be used by the I3C module. When the I3C module is enabled with I3C Low-Voltage Buffers selected, all the other pad buffers are disabled.
  2. 2.When the I3C Low-Voltage Buffers are enabled, the Slew Rate Limiting Control SLEW bits in RxyI2C register are ignored, although the Pull-Up Selection PU bits in RxyI2C register remain operational. Since the MIPI I3C® Specification does not require the Target to have pull-ups, it is recommended to disable weak pull-ups on the I3C pads through the PU bits and the WPUx registers. Enabling pull-ups on I3C pads may affect I3C performance.
CAUTION: After the I3C Low-Voltage Buffer is enabled using the IOLVCON register, there is a small delay before the I3C Low-Voltage Buffers are actually activated, during which the I3C module requests for the bandgap reference voltage. The user can eliminate this delay by requesting for the bandgap reference beforehand by enabling the FVR module (set EN bit to 1 in FVRCON register).
CAUTION: The user must ensure to provide this delay when initializing the module after selecting the I3C Low-Voltage Buffer and before enabling the I3C module. If sufficient delay is not provided, then the I3C module may be unresponsive to the traffic on the bus after it is enabled until the bandgap reference becomes available. Refer to the “Module Setup and Usage”section for recommended module initialization process.