LSF0108-Q1: Using LSF0108-Q1 as a switching device without level-shifting

Gennady Burdo

Part Number: LSF0108-Q1

Hi.

We are using LSF0108-Q1 just as ON/OFF switch for QSPI 1.8V interface. Signals are driven by a push-pull drivers at 1.8V level. Expected output level after the LSF0108-Q1 switches need to be 0 - 1.8V levels as well. We want to make sure that we understand the datasheet correctly

Assuming we are driving EN pin directly by a push-pull driver to drive the EN pin. Its voltage level to enable LSF0108-Q1 switch conduction state needs to be 2.6V (*1.8V + 0.8V) or higher, correct? Having EN pin voltage level reach only 1.8V will cause output clamping to about 1.2V, correct?
Assuming the following implementation, voltage on A1 pin will not reach 1.8V unless a pull-up to 1.8V resistor on A1 is used, correct?

9 days ago

+1 Nathan Co 9 days ago

TI__Prodigy 190 points

Hi Gennady,

We are still looking into this and will provide an update shortly.

Regards,

Nathan

0 Nathan Co 8 days ago

TI__Prodigy 190 points

Hi Gennady,

It is generally recommended to use an open drain driver to configure the enable pin. As per this logic minute video: Using the Enable Pin with the LSF Family | Video | TI.com

However, if you continue using the push pull driver, please refer to the diagram of a device with similar architecture below.

As you said the outputs will clamp at 1.2V if you bias the EN pin to VrefA but the pull-up resistors on the output side will drive the remainder of the signal to 1.8V.

0 Gennady Burdo 7 days ago in reply to Nathan Co

Prodigy 10 points

Thanks a lot, Nathan.

We will update our design.

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LSF0108-Q1: Using LSF0108-Q1 as a switching device without level-shifting