SPRUJ55D September 2023 – July 2025 AM263P2 , AM263P2-Q1 , AM263P4 , AM263P4-Q1
The ADCSOCxCTRL.EXTCHSEL field for each SOC can be used to automatically control an external mux with digital output pins ADCxEXTMUX[1:0]. This functionality enables the application to add additional ADC channels using an external mux, with minimal software overhead. The ADCxEXTMUXy outputs can be mapped to GPIO pins by configuring the associated IOMUX to use the ADC_EXTCH_XBAR signal accordingly. The EXTCHSEL field supports up to 2-bit muxes, but fewer mux selection output pins can be configured if desired.
To select a specific channel on the external mux, configure ADCSOCxCTRL.CHSEL to select the ADC pin that is connected to the mux output, and configure ADCSOCxCTRL.EXTCHSEL to select the desired mux input channel. There are a variety of potential mux topologies possible. A basic example can be a single external mux connected to a single ADC input channel.
Figure 7-114 ADC with External Input MuxWhen using an external channel mux, make sure to comprehend the mux selection and switching delay in the sample/hold time requirement for the SOC. This requirement includes the propagation delay for the output X-BAR (if this is used to configure the mux selection pin), any mux switching delays, and the total resistance and capacitance added to the ADC input network by the external mux device. For more information on calculating the acquisition window size, see Section 7.5.2.20.2.
There is also an External mux preselect function to allow some of the settling time to be pipelined with during the previous samples conversion time when ADC SOC sequencing is deterministic.
Refer to the ADC_selectSOCExtChannel() & ADC_enableExtMuxPreselect() APIs.
Refer to the ADC_selectSOCExtChannel() & ADC_enableExtMuxPreselect() APIs.