7.3.6 Frequency Synchronization

Another feature of the LM2586 is the ability to synchronize the switching frequency to an external source, using the sync pin (pin 6). This feature allows the user to parallel multiple devices to deliver more output power.

A negative falling pulse applied to the sync pin will synchronize the LM2586 to an external oscillator (see Figure 24 and Figure 25).

Use of this feature enables the LM2586 to be synchronized to an external oscillator, such as a system clock. This operation allows multiple power supplies to operate at the same frequency, thus eliminating frequency-related noise problems.

Figure 24. Frequency Synchronization

Figure 25. Waveforms of a Synchronized 12-V Boost Regulator

The scope photo in Figure 25 shows a LM2586 12-V boost regulator synchronized to a 200-kHz signal. There is a 700-ns delay between the falling edge of the sync signal and the turning on of the switch.

Figure 26. Boost Regulator