LM61460: Synchronisation

Franz Haselsteiner

Part Number: LM61460

Is the possible synchronisation frequency independent from resistor on RT?

For example wth RT=33k2 nominal switching frequency would be 400kHz. Can the oscillator be synchronized to 300kHz or 540kHz?

We want to change the frequency depending on running system application between these values.

Thanks

over 3 years ago

0 Jimmy Hua over 3 years ago

TI__Guru 50120 points

Hi Franz,

The EN/SYNC feature of this device allows external synchronization. Please refer to Section 8.3.2 for more information.

You can have the RT resistor set the initial startup switching frequency. Once the start-up sequence is properly initialized, an external clock can be injected through an AC coupling capacitor into the EN/SYNC pin of the device to dynamically control the switching frequency. This external clock should then override the RT resistor.

Regards,

Jimmy

0 Franz Haselsteiner over 3 years ago in reply to Jimmy Hua

Prodigy 20 points

There is no restriction on synchronisation frequency, depending on RT?

So I can use RT=33k2 and synchronize after start up to 1MHz.

Or I can use RT=6k and synchronize to 300kHz.

Is this correct?

0 Jimmy Hua over 3 years ago in reply to Franz Haselsteiner

TI__Guru 50120 points

Hi Franz,

The external synchronization can be between 200kHz and 2.2MHz as stated in the datasheet. If the external synchronization is removed, the RT resistor should set the internal clock back to the set RT value.

Regards,

Jimmy

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LM61460: Synchronisation