LSF0102: LSF0102DCUR Sch Review Check for I2C

chiu wesley

Prodigy 50 points

Part Number: LSF0102
Other Parts Discussed in Thread: TCA9802, TCA9554A, TCA9803

HI TI TEAM:

please Check Circuit we application for DDR4 SO-DIMM(3.3V) -->FPGA PS SIDE(1.8V)

USED I2C interface.

We hope to have better compatibility.

If you have any Concern, let me know.

Thank you a lot!

6 months ago

0 chiu wesley 6 months ago

Prodigy 50 points

LSF0102DCUR_2024-0512_SOD.pdf

0 chiu wesley 6 months ago in reply to chiu wesley

Prodigy 50 points

please Check PDF file circuit.Thank you^^

0 Jack Guan 6 months ago in reply to chiu wesley

TI__Mastermind 25431 points

Hey Chiu,

It looks OK- no immediate concerns from what I see. The external pullups used on the I/Os of the device will ultimately determine the achievable data rate, please ensure that they are sized correctly to meet system needs.

I2C Bus Pull-Up Resistor Calculation

Regards,

Jack

0 chiu wesley 6 months ago in reply to Jack Guan

Prodigy 50 points

HI Jack:

The part of our Concern is that the voltage of LSF0102 in VOL is not close to 0V (VOL> VIL voltage), which will cause Sodimm of EEPROM reading and writing errors, or cause other devices to respond without ACK.
So we consider using TCA9208. Is this part of TI recommended?
The speed of we use I2C is below 400K.

We hope to have better I2C compatibility!

0 chiu wesley 6 months ago in reply to chiu wesley

Prodigy 50 points

Hi Jack:

Sorry!Update model TCA9802

0 Clemens Ladisch 6 months ago in reply to chiu wesley

Guru 277650 points

Yes, the LSF is only a passive switch. To improve VOL, you can use an I²C buffer like the TCA980x.

0 chiu wesley 6 months ago in reply to Clemens Ladisch

Prodigy 50 points

Hi Jack:

We Modify Circuit change to TCA9802DGKT (U26 & U27) , please Check pdf file.

NL/ is DNP-->no mount.

If you have any Concern, let me know.

I have a Concern, TCA9802 B SIDE ---> To FPGA PS SIDE.
Is TCA9802 B SIDE Not Pull Hi it is correct? (R691 & R692 & R694 & R695 is no mount)

Thank you a lot^^

TCA9802_1.pdf

0 Clemens Ladisch 6 months ago in reply to chiu wesley

Guru 277650 points

Looks OK.

You are correct that pull-ups on the B side must be removed. (Switches like the TCA9554A require pull-ups, so you cannot use them on the B side. But they are fine on the A side.)

0 Jack Guan 6 months ago in reply to Clemens Ladisch

TI__Mastermind 25431 points

Hey Chiu,

No immediate concerns from my side. TCA9803 allows for VCCA > VCCB operation so current operation is OK. The EN pin is also internally pulled up to VCCA via a ~250kohm pullup so it can be left floating if desired as well.

Regards,

Jack

0 chiu wesley 6 months ago in reply to Clemens Ladisch

Prodigy 50 points

HI Clemens:

Thank you for your support^^

0 chiu wesley 6 months ago in reply to Jack Guan

Prodigy 50 points

HI Jack:

Thank you for your support^^

0 chiu wesley 6 months ago in reply to Clemens Ladisch

Prodigy 50 points

HI Jack & Clemens:

I want to know ,

If TCA9802 B SIDE PULL UP resistance (4.7K)
What will happen or problem?

0 Clemens Ladisch 6 months ago in reply to chiu wesley

Guru 277650 points

When another device pulls the line on side B low without sinking current from the TCA980x's current source, then the TCA980x might not detect that the low signal comes from another device, and might not propagate the low signal to the A side.

0 chiu wesley 6 months ago in reply to Clemens Ladisch

Prodigy 50 points

HI Clemens:

got it .Thank you a lot^^

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LSF0102: LSF0102DCUR Sch Review Check for I2C