LSF0204-Q1: SPI Application

Evan Wang

Part Number: LSF0204-Q1
Other Parts Discussed in Thread: TXB0304, TXB0106-Q1, , SN74AXC4T774-Q1

Hi TI Expert,

We try to find the AEC-Q100 version of TXB0304 on ti.com but the TXB0106-Q1 could not support 100Mbps under 1.8V VCCA <-> 3.3V VCCB scenario.

I think the LSF0204-Q1 might work but I'm not sure about that since the datasheet didn't mention the detailed operating condition.

In short, we need a AEC-Q100 level shifter supporting 1.8V <-> 3.3V for SPI interface with 100Mbps capability.

Kindly let us know whether LSF0204-Q1 will work or you have a better suggestion.

Thank you.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 321080 points

Just use the SN74AXC4T774-Q1.

0 Joshua Salinas over 2 years ago

TI__Mastermind 32760 points

Hello Evan,

If you are using this for SPI, then I would recommend TXU0304-Q1 or the AXC4T774 like Clemens mentioned. You shouldn't use auto-direction sensing devices unless your application requires it.

Regards,

Josh

0 Evan Wang over 2 years ago in reply to Joshua Salinas

TI__Genius 11630 points

Hi All,

Customer need the Quad mode SPI so auto-direction is needed.

Could you recommend another one to us?

Thank you.

0 Clemens Ladisch over 2 years ago in reply to Evan Wang

Guru 321080 points

To achive high speeds, the LSF would require very strong pull-up resistors, and thus would also require both other devices to have a very high drive strength (many tens of mA). This is unlikely to be the case.

There is no automotive-qualified device that can handle this.

0 Evan Wang over 2 years ago in reply to Clemens Ladisch

TI__Genius 11630 points

Hi Clemens,

Clemens Ladisch said:
To achive high speeds, the LSF would require very strong pull-up resistors, and thus would also require both other devices to have a very high drive strength (many tens of mA). This is unlikely to be the case.

The LSF0204-Q1 can support 100MHz but does it means we can support 100Mbps for QSPI?

I'm confused about the limitation here.

Could you kindly share more background of this limitation?

Thank you.

0 Clemens Ladisch over 2 years ago in reply to Evan Wang

Guru 321080 points

The LSF is a passive switch; the high output voltage is generated only by the pull-up resistors. To get fast rising edges, you must be able to overcome the circuit's capacitances quickly, so you need a high pull-up current. For a low signal, the devices on both sides must be able to sink the current through these resistors. The specific resistor values depend on the actual capacitance, but it is very likely that they are far outside the limits of what your devices can support.

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LSF0204-Q1: SPI Application