LSF0102: B-side outputs stuck at 1V whilst translating from 1.0V (A side) to 3.6V (B side)

leonardo sala

Part Number: LSF0102

Tool/software:

In spite of having followed this schematic (from the DS), with 1.0V instead of 1.2V (VrefA) and 3.6V instead of 1.8V (VrefB), B1 and B2 remain stuck at 1V, regardless of the A1 and A2 levels.

1 month ago

0 Jack Guan 1 month ago

TI__Mastermind 22141 points

Hey Leonardo,

Please note pullups would be needed on the high side (B-side in this case) as the device has open drain outputs. The measured voltage on the EN node should be roughly around 1.8V. Can you confirm on your end? You may also share your specific schematic for further debugging.

Thanks,

Jack

0 leonardo sala 1 month ago in reply to Jack Guan

Prodigy 10 points

Hello Jack!

Thanks for the quick reply.

Yes, we do have both:

1. The pull-ups

2. The 200kOhm resistor connecting VrefB and En to the 3.6V

On VrefB we are measuring a few mV; should we assume that the part is broken ?

VrefB was previously exposed to 3.6V directly: is it possibly a reason for the mulfunctioning ?

Thx

0 Jack Guan 1 month ago in reply to leonardo sala

TI__Mastermind 22141 points

Hey Leonardo,

It is possible the unit may be damaged since the 200kohm bias resistor was previously absent.

VREFB shouldn't be connected directly to 3.6V as this will result in a leakage current through the internal FET (limited by the 200kohm bias resistor). If configured correctly, it should be shorted to EN, and then pulled up via 200kohm to 3.6V. Here is a Logic Minute Video that covers this: https://www.ti.com/video/5614304068001

Can we swap out the unit and retest?

Regards,

Jack

+1 leonardo sala 1 month ago in reply to Jack Guan

Prodigy 10 points

Hi Jack,

yes, confirmed: the part was damaged indeed.

Thanks a lot, problem solved and 1.8V measured.on Vrefb

Logic

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LSF0102: B-side outputs stuck at 1V whilst translating from 1.0V (A side) to 3.6V (B side)