In this scenario the SoC or MCU on-chip oscillator cannot accept an LVCMOS or logic-compatible signal greater than the equivalent signal generated by the XTAL-oscillator combination. Thus, the downstream SoC/MCU oscillator is enabled and will internally amplify the signal to the correct level. Irrespective of the VDD (3.3 or 1.8 V), a NanoDrive level equivalent to AA3 is recommended. In this example, the full part number is SiT15xxAI-xx-AA3-32.768.