Clock

Source

EN/SYNC

VIN

EN/SYNC

VIN

14

LMR23630

SNVSAH2C – DECEMBER 2015 – REVISED JUNE 2017

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8.3.4 Enable/Sync

The voltage on the EN pin controls the ON or OFF operation of LMR23630. A voltage less than 1 V (typical)

shuts down the device while a voltage higher than 1.6 V (typical) is required to start the regulator. The EN pin is

an input and cannot be left open or floating. The simplest way to enable the operation of the LMR23630 is to

precision system UVLO level for the converter. System UVLO can be used for supplies operating from utility

power as well as battery power. It can be used for sequencing, ensuring reliable operation, or supply protection,

such as a battery discharge level. An external logic signal can also be used to drive EN input for system

sequencing and protection.

Figure 16. System UVLO by Enable Divider

The EN pin also can be used to synchronize the internal oscillator to an external clock. The internal oscillator can

be synchronized by AC-coupling a positive edge into the EN pin. The AC-coupled peak-to-peak voltage at the EN

pin must exceed the SYNC amplitude threshold of 2.8 V (typical) to trip the internal synchronization pulse

detector, and the minimum SYNC clock ON-time and OFF-time must be longer than 100 ns (typical). A 3.3-V or a

synchronized to an external clock from 200 kHz to 2.2 MHz. Figure 18 and Figure 19 show the device

synchronized to an external system clock.

Figure 17. Synchronize to External Clock