TAS5548 How to Synchronize Two Parts

Sadanori Kato

Hi,

Is it possible to share an external crystal in order to synchronize two TAS5548s and decrease the external components as below ?

Best regards,
Kato

over 9 years ago

0 Mike Tripoli over 9 years ago

Genius 3295 points

Hi Kato,

Judging from what I see in the datasheet, it "looks like" this is a "standard" oscillator circuit wherein the crystal is in parallel with an inverter (internally). As such, one should be able to externally buffer the "output" side (pin 12) to drive the input of another device. The only question is if one can "overdrive" the input this way on the second device, leaving the output (pin 12) of the second device unconnected. A single gate buffer should do it. Seems reasonable to do...

Mike Tripoli

0 Sadanori Kato over 9 years ago in reply to Mike Tripoli

Guru 36540 points

Hi Mike-san,

Thank you for your quick response.

Do you have results of that your customers have adopted this method ?

Best regards,
Kato

0 Mike Tripoli over 9 years ago in reply to Sadanori Kato

Genius 3295 points

Hi Kato-san,

I have experience with this "technique", not this specific device. In the past, the devices I've used have either been designed to allow this type of operation ("crystal" or "clock" input on the same pin) or through working with the manufacturer of the device verified that the input can be "over-driven" by a clock pulse as opposed to using a crystal. It should be an easy thing to test; as I say, use a buffer with high output current. For instance, this device should do it:

http://www.ti.com/lit/ds/symlink/sn74lvc1g126.pdf

Mike Tripoli

0 Sadanori Kato over 9 years ago in reply to Mike Tripoli

Guru 36540 points

Hi Mike-san,

Thank you for your support.

I modified the schematic to syncronize two parts as below since the XTALI and XTALO pins are the 1.8V tolerant.
Is my understanding correct ?

Best regards,
Kato

0 Mike Tripoli over 9 years ago in reply to Sadanori Kato

Genius 3295 points

Hi Kato-san,

You'll want to use the "output" side of the circuit, pin 12.

Mike Tripoli

0 Sadanori Kato over 9 years ago in reply to Mike Tripoli

Guru 36540 points

Hi Mike-san,

Thank you for confirming.
I understood as the following schematic.

Best regards,
Kato

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TAS5548 How to Synchronize Two Parts