LSF0108: LSF0108

Rohini E

Prodigy 80 points

Part Number: LSF0108
Other Parts Discussed in Thread: TXV0108, TXB0304

Tool/software:

Hi Team,

We are using LSF0108 in one of our designs to level translate signals between FPGA IO(1.2V) and USB3320

The max signal frequency is 60MHz and the data are bi-directional.

We have connected 2.5V to VREFB to maintain the BIAS Voltage

Could you let us know below circuitry is ok for the scenario mentioned

Thanks,

Rohini

10 months ago

0 Clemens Ladisch 10 months ago

Guru 319150 points

This might work. But I do not know if the pull-up resistors are sized correctly. Both the other devices must be able to sink the total current through both resistors, and the low-pass filter formed by the pull-up resistors and the trace/device capcitances must not filter out your 60 MHz signals. I do not know these parameters.

A buffered, direction-controlled translator like the TXV0108 might be a better idea; ULPI has the DIR signal for this.

0 Rohini E 10 months ago in reply to Clemens Ladisch

Prodigy 80 points

Hi Clemens,

Thank you for the reply

1. I have updated the Pullup values for

Data frequency of 60MHz

IOL of MAX10 is 10mA

IOL of USB3320 is 8mA

Pin Capacitance @1.8V device is 4pF

Pin capacitance @1.2V device is 10pF

As per calculated below calculation we are using 475E(1% Tolerance) Pullup on 1.2V side and 576E(1% Tolerance) pullup on 1.8V side. Please confirm the tuned pullup values are good to go

USB	Va	1.2				MAX10
	Ra	475
	Ca	2.3
	DATARATE	152.5553013	MBps

	Vb	1.8				USB3320
	Rb	576
	Cb	4
	DATARATE	72.33796296	MBps	5.651315789	Iol

2. LSF0108 bias voltage is 0.8V and we are translating signals from 1.8V to 1.2V and vise versa

To maintain the Bias voltage, we have connected 2.5V to VrefB but pullups(576E) on I/Os are connected to 1.8V. Hope this is fine

Awaiting for your reply

Thanks,

Rohini

0 Clemens Ladisch 10 months ago in reply to Rohini E

Guru 319150 points

The MAX10's drive strength at 1.2 V is only 2 mA, but your total pull-up current is more than 5 mA. And you have to include the capacitances of the traces and of the LSF.

As far as I can see, ULPI has pull-down resistors on the data lines, so you must not use a translator that requires pull-ups.

0 Rohini E 10 months ago in reply to Clemens Ladisch

Prodigy 80 points

Hi Clements,

Will TXB0304 for our application

Main consideration is 1.2V to 1.8V Bidirectional Translation and 60MHz data flow support

Thanks & regards,

Rohini

0 Clemens Ladisch 10 months ago in reply to Rohini E

Guru 319150 points

No; the TXB does not work with pull-up/-down resistors, and it does not support more than 50 MHz at these voltages.

0 Rohini E 10 months ago in reply to Clemens Ladisch

Prodigy 80 points

Do you have any suggestion for our application

Main consideration is 1.2V to 1.8V Bidirectional Translation and 60MHz data flow support

Thanks & regards,

Rohini

0 Clemens Ladisch 10 months ago in reply to Rohini E

Guru 319150 points

TXV0108.

Consider redesigning your system to use 1.8 V I/Os on the FPGA.

Logic

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LSF0108: LSF0108