About LSF0204 application

Shu-Cheng LIN

Other Parts Discussed in Thread: LSF0204

Hi Sirs,

Sorry to bother you.

We would like use LSF0204 for Fast SPI signal, some thing need confirm.

1.If we application for Fast SPI signal, do we need external pull up resistor?? because we only saw 100MHz for OD signal, how about PP bandwidth??

2.At datasheet page 13 note "However, if either output is push-pull, data must be unidirectional or the outputs must be 3-state and be controlled by some direction-control mechanism to prevent HIGH-to-LOW contentions in either direction.".If we application is bi-direction, we must use open drain type?

Thanks for your reply.

over 9 years ago

0 Clemens Ladisch over 9 years ago

Guru 317480 points

In theory, SPI signals are not bidirectional. Assuming that you did not need a level shifter, how would your circuit handle the changing directions?

0 Shu-Cheng LIN over 9 years ago in reply to Clemens Ladisch

Guru 11785 points

Hi Ladisch

Thanks for your reply.

For SPI spec

"A multi I/O SPI device is capable of supporting increased bandwidth or throughput from a single device. A dual I/O (two-bit data bus) interface enables transfer rates to double compared to the standard serial Flash memory devices. A quad I/O (four-bit data bus) interface improves throughput four times."

We focus at IO 0-3, the data line is bi-direction.

So could you help double confirm our question again?

Many thanks!!

0 Clemens Ladisch over 9 years ago in reply to Shu-Cheng LIN

Guru 317480 points

What are the actual chips you're trying to connect together?

0 Shu-Cheng LIN over 9 years ago in reply to Clemens Ladisch

Guru 11785 points

Hi Clemens,
If don't care link chip.
Only focus SPI IO0-3 data line.
What is the max bandwidth on LSF0204??
Push pull max rate???
Open drain max rate??? >100MHZ??
Also i saw The 3-dB point of the LSF family is ≈600MHz this description on datasheet
It's confuse us...
Thanks for your reply.

0 Clemens Ladisch over 9 years ago in reply to Shu-Cheng LIN

Guru 317480 points

The bandwidth depends on the parameters of your circuit (voltage, drive strength, pull-up resistors, capacitance). See the datasheet.

The -3 dB point is explained in the datasheet; it is not important for digital signals.

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About LSF0204 application