SPRAD21I May 2022 – September 2025 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP , AM62A1-Q1 , AM62A3 , AM62A3-Q1 , AM62A7 , AM62A7-Q1 , AM62D-Q1 , AM62P , AM62P-Q1
Series resistor (22Ω) on the clock outputs are recommended to be added near to the processor clock output (for MCSPI, MCASP) pins since the clock is also being used for retiming. The series resistor additionally supports possible reflection control (signal distortion).
For MMC0, MMC1, MMC2, OSPI0, GPMC0 interfaces, an unbonded pad is used (internal) for retiming (loopback). We do not use the same clock that is sent across the PCB to the attached device for our capture clock. We branch the output clock into two paths inside the device, where the clock is sent to two separate IO cells. One IO cell is connected to a package ball, which is used to source a clock to the attached device. The other IO cell is unbounded (not connected to any package ball). The clock used as the receive capture clock is sent out through the unbonded IO cell and looped back into the device before being used as the capture clock. We do this so the clock has the same delay that is inserted on the clock going out to the attached device and the same delay that is inserted on the data coming back in from the attached device. The unbonded IO cell pad never experiences the voltage step that is produced on the source end of a PCB signal trace. A low value series resistor (0Ω to start) is recommended (provisioned) to control possible signal reflections (signal integrity purpose).