LSF0102: Design with LSF0102

Max Guan

Intellectual 1350 points

Part Number: LSF0102
Other Parts Discussed in Thread: PCA9306

Hi,

my customer wants to use LSF0102 in the design and would like to know:

1. The LSF0102 supports both pushpull and opendrian. How the IC work with the config accordingly?

2. Will there be leakage concern from A to B or revert? If so how could customer improve the design to avoid it?

Thanks

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 297310 points

1. There is nothing special about these modes. When you are driving it with open-drain signals, you need pull-up resistors, so you have a valid high-level input voltage in any case. (The LSF's outputs always are open drain.)

2. The LSF is a passive switch; for low signals, the A and B pins are connected directly together. There also is a leakage current from Vref_B to Vref_A; it is limited only by the 200 kΩ resistor.

See [FAQ] How do the LSF translators work?

0 Max Guan over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 1350 points

Thank you Clemens.

We had discussion on PCA9306 about similar leakage questions. And may I know if below connection could work for LSF0102 as well?

Most likely it will also settle the Vref leakage concerns.

0 Dylan Hubbard over 3 years ago in reply to Max Guan

TI__Mastermind 45115 points

Hey Max,

Is this device being used for I2C?

0 Max Guan over 3 years ago in reply to Dylan Hubbard

TI__Intellectual 1350 points

Hi Dylan, correct it is for I2C.

0 Dylan Hubbard over 3 years ago in reply to Max Guan

TI__Mastermind 45115 points

Hey Max,

Then yes this will also apply for the LSF device.

0 Max Guan over 3 years ago in reply to Dylan Hubbard

TI__Intellectual 1350 points

Hi Dylan,

Thank you for your confirmation on that.

Could the LSF0102 could work with same voltage transition in this case? For example both sides pulled high to 3.3V or 1.8V?

And could EN pin be tied GPIO with 200kOhm or it could only be pulled to any of later pull-high rails?

Thank you.

Max

0 Clemens Ladisch over 3 years ago in reply to Max Guan

Guru 297310 points

The LSF0102 and PCA9306 are essentialy identical.

The 200 kΩ resistor is needed only when Vref1/2 are connected, to limit the current flowing through these pins. When you leave VrefX open and connect EN to the lower voltage, you can connect it directly.

0 Max Guan over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 1350 points

Thank you Clemens.

And to double confirm. This connection could support 1.8V to 1.8V or 3.3V to 3.3V transition correct?

0 Clemens Ladisch over 3 years ago in reply to Max Guan

Guru 297310 points

Yes.

0 Max Guan over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 1350 points

Thank you.

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LSF0102: Design with LSF0102