LSF0204: driving too strong?

user4979899

Expert 3080 points

Part Number: LSF0204

Hi Sir,

Here is the waveform from LSF0204 which measurement from 1.8V side I/O.

Net name:

MDC_BCM16K_1P8V_R

MDIO_BCM16K_1P8V_R

We found the mater driving too strong, and already tuning the pull up resistor value as 91 ohm, but still can see this waveform,

DO you have any idea how to tuning the pull up resistor value to fix it?

Thanks

over 5 years ago

0 Karan Kotadia over 5 years ago

TI__Genius 16725 points

Hi Anne,

Can you provide a schematic of your LSF device? Your issue is that the device has over shoot because of a strong pullup? Can you increase your pullup resistance?

What voltages is the LSF being used to translate?

Your removed the frequency of operation and voltage from your scope shot, I would like to know this.

Thanks!

-Karan

0 user4979899 over 5 years ago in reply to Karan Kotadia

TI__Expert 3080 points

Hi Karan,

I am asking if customer can provide the schematic or scope shot with frequency but didn't have feedback yet.

and it is for 1.8V to 3.3V translate in LSF0204.

0 Dylan Hubbard over 5 years ago in reply to user4979899

TI__Mastermind 44610 points

Hi Anne,

A faster dv/dt will result in overshoot like this. Since the pull-ups determine this slew rate, then using larger resistors to reduce that slew should help. 1k is overkill for most I2C speeds.

Logic

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LSF0204: driving too strong?