LSF0102-Q1: Buffer Voltage level issue LSF0102QDCURQ1

JIJU RAJ K

Part Number: LSF0102-Q1
Other Parts Discussed in Thread: TXU0202-Q1

Hi,

This IC is used as a bidirectional UART. In the schematics shown below, The output A port is 1.8V level and output B is 3.3V.

The issue is the B2 voltage level is 1.8V. What is the issue?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 257900 points

The LSF is a passive switch and outputs open-drain signals. You need a pull-up resistor at B2, and a pull-up resistor at A1 would make the signal more robust.

For UART signals, a buffered translator like the TXU0202-Q1 would be a better solution.

0 JIJU RAJ K over 1 year ago in reply to Clemens Ladisch

Prodigy 25 points

Hi,

We removed the pull-up 200K, directly connected to 3.3V. After the change, we got 3.3V in the RX line.

Is any pull-up resistor needed in the VCCB and EN?

If it's directly connected to the buffer anything is happens in the buffer?

Regards,

JIJU RAJ K

0 Clemens Ladisch over 1 year ago in reply to JIJU RAJ K

Guru 257900 points

The 200 kΩ resistor is needed for the LSF to work correctly. Without it, a high current leaks into the lower supply, and the low-voltage outputs are not clamped to Vref_A.

Pins 2 and 7 are not power supplies but reference voltage inputs. And the LSF is not a buffer. See [FAQ] How do the LSF translators work?

0 JIJU RAJ K over 1 year ago in reply to Clemens Ladisch

Prodigy 25 points

Hi Clemens,

Is the TXU0202QDCURQ1 IC AECQ100 qualified?

Regards,

JIJU RAJ K

0 Clemens Ladisch over 1 year ago in reply to JIJU RAJ K

Guru 257900 points

ti.com/quality-reliability-packaging-download/report?opn=TXU0202QDCURQ1 lists the AEC Q100 tests.

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LSF0102-Q1: Buffer Voltage level issue LSF0102QDCURQ1