Figure 2-6 shows the different clock options for the ADS127L11EVM. The default position for jumper (JP7) 1-2 routes the PHI digital controller board clock to the CLK pin on the ADS127L11 (U3). If the ADS127L11EVM is used without the PHI board, then change the shunt on jumper (JP7) to position 2-3 to directly route the local clock to ADS127L11 (U3).

Jumper (JP6) selects either the local 25-MHz oscillator (Y1) on the ADS127L11EVM board, or an external clock supplied on the SMA connector (J14). The default position for jumper (JP6) 1-2 selects the local 25-MHz oscillator (Y1). The ADS127L11EVM-PDK-GUI software by default uses the 24-MHz PHI clock source, but can select the board clock source, 25-MHz (Y1) oscillator, or SMA connector (J14).

If the local 25-MHz oscillator (Y1) is used, then remove the shunt on jumper (JP3) to enable the oscillator. If an external clock source is used, use a CMOS square-wave signal with an amplitude equal to IOVDD (1.8 V with the PHI board) and a frequency within the specified range of the ADS127L11.

Figure 2-6 Clock Tree