SNVSBW1B December 2021 – October 2023 LM63460-Q1
PRODUCTION DATA
Use the EN/SYNC pin of the LM63460-Q1 to synchronize the internal oscillator to an external clock signal ranging from 200 kHz to 2.2 MHz. The internal oscillator can be synchronized by AC coupling a positive clock edge to EN/SYNC, as shown in Figure 8-1.
It is recommended to keep the parallel combination value of RENT and RENB in the 100-kΩ range. RENT is required for synchronization, but RENB can be left unmounted. The external clock must be off before start-up to allow proper start-up sequencing.
Referring to Figure 8-2, the AC-coupled voltage edge at EN/SYNC must exceed the SYNC amplitude threshold, VEN_SYNC, to trip the internal synchronization pulse detector. In addition, the minimum EN/SYNC rising pulse and falling pulse durations must be longer than tSYNC_EDGE and shorter than the blanking time, tB. A 3.3-V or higher amplitude pulse signal coupled through a 1-nF capacitor, CSYNC, is suggested.
After a valid synchronization signal is applied for 2048 cycles, the clock frequency quickly changes to that of the applied signal. Synchronization overrides spread spectrum, turning it off.