LSF0102: LSF0102 VS TXS0102

Shay Mor

Intellectual 870 points

Part Number: LSF0102
Other Parts Discussed in Thread: TXS0102, TPS54527, LSF0204

Hi,

I'm considering using the LSF0102 component, but i worry about the leakage between VCCB(3.3V) to VCCA(1.8).

1. What is the diffrent between LSF0102 VS TXS0102 about the leakage?

2. Does this TXS0102 have more or less leakage between the VCCB(3.3V) to VCCA(1.8V)?

3. in my design i connect the VCCA line to power supply with 50K FB resistor (TPS54527-output=1.8V), if I use the LSF0102 and turn on the VCCB (3.3) what will be the voltage level in the output supply (TPS54527-output=1.8V) when the power supply is off(EN pin of TPS54527= "0")

Attached photos:

over 5 years ago

0 Dylan Hubbard over 5 years ago

TI__Mastermind 45675 points

Hey Shay,

The supply circuitry for both devices is quite similar, so they are likely to have similar leakage. There's a lot to explain for question 3 which I will use the video to help with. It will explain the bias circuitry of the device (in greater detail) which should answer your questions with certain scenarios of your power supply.

https://training.ti.com/tlm-lsf-bias?context=1134826-1139264-1134790

0 Shay Mor over 5 years ago in reply to Dylan Hubbard

Intellectual 870 points

Thanks,

I already saw this video,

1. Is the 200K is must? if I what to change this 200K value can I? if yes, what is the min and max value?

2. Why the 200k in this LSF0102 is not an internally?

3. Is the FET transistor on VCCB and VCCA is only for protection the chip?

0 Dylan Hubbard over 5 years ago in reply to Shay Mor

TI__Mastermind 45675 points

Hey Shay,

Yes the 200k is a must as indicated in the video. We do have some LSF device that have it internal like the LSF0204. Its there to properly bias the device, as you see in the video, its connected to the gates of the data channel FETs.

0 Shay Mor over 5 years ago in reply to Dylan Hubbard

Intellectual 870 points

in LSF0204 when either VCC Input is 0V, are all I/Os Outputs are Disabled and Become High Impedance?

0 Shay Mor over 5 years ago in reply to Dylan Hubbard

Intellectual 870 points

Why the 200k in this LSF0102 is not an internally?

0 Clemens Ladisch over 5 years ago in reply to Shay Mor

Guru 316440 points

Then Vref_A is 0 V, current can still flow from Vref_B to Vref_A. The only way to disable the LSF is to pull then EN pin low.

In theory, it's possible to use the LSF in a different way (connect EN directly to the lower supply, and use Vref_A/Vref_B as an additional channel). This requires a pull-up resistor on the output even when down-shifting, and in practice, nobody does this.

0 Dylan Hubbard over 5 years ago in reply to Shay Mor

TI__Mastermind 45675 points

Hi Shay,

There are devices with the resistor internal, they would be the LSF02xx line of devices.

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LSF0102: LSF0102 VS TXS0102