TXS0102DCUR and TXS0104EPWR logic levels SPECs concerns.

Da-Wei Kuo

Prodigy 20 points

If the following two levelshifters' logic levels SPECs does not match with the main chip logic level.

Will there be any risks involved?

e.g.

Vol 0.4 > VIL 0.15
main chip

TXS0102DCUR

VOH VDDIO*0.85(2.805V) < VIH VCCI-0.4V(2.9V).
VOL VDDIO*0.15(0.495V) > VIL 0.15
VDDIO = VCCI = 3.3V

main chip

TXS0104EPWR

VOH EVDD-0.45V( 1.35V) > VCCI-0.2V( 1.6V)
VOL 0.45V > VIL 0.15V
main chip

TXS0104EPWR

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316760 points

The TXS values are not actually switching levels; see [FAQ] Why are the TXS01xx VIH/VIL specifications so stringent? The TXS will pass through low-level voltages.

0 Jack Guan over 1 year ago

TI__Mastermind 40216 points

Hey Da-Wei,

In addition to Clemens' response, you may also see the footnote below the recommended operating conditions:

Here is an app note for further info:

Factors Affecting VOL for TXS and LSF Auto-bidirectional Translation Devices

Please let us know if you have any further questions.

Thanks,

Jack

0 Da-Wei Kuo over 1 year ago in reply to Clemens Ladisch

Prodigy 20 points

Hi Clemen

Thanks for the information, I get the idea of VIL. but why is VIH also stringent.

How can VIH affect VOH if N2 is disconnected?

BTW, what level should refer to if I want to ensure that level shifter is translating correctly?

0 Clemens Ladisch over 1 year ago in reply to Da-Wei Kuo

Guru 316760 points

For voltages lower then VCCA, the TXS works as an analog switch. It is expected that the pull-up resistor forces the high-level voltage to be near VCCA; a pull-down resistor or other load would not make sense.

What is your actual application? How many signals in each direction are there?

0 Da-Wei Kuo over 1 year ago in reply to Clemens Ladisch

Prodigy 20 points

Thanks for the explaination, It’s clear to me now.

0 Da-Wei Kuo over 1 year ago

Prodigy 20 points

I have a further question here.

If VIL = 0.15V VOL = 0.4V Can I assume that the voltage drop across the pass-gate transistor is 0.25V?

Cause in our application, Device VOL max is 0.495V, and CPU VIL max is 0.54V.

So when our device sends a low signal to the CPU, the voltage will over the CPU SPEC. 0.495V + 0.25V > 0.54V

0 Clemens Ladisch over 1 year ago in reply to Da-Wei Kuo

Guru 316760 points

The worst-case V_OL of the TXS is specified for a test current of 1 mA. In other words, the worst-case resistance of the switch is 250 Ω, and changing the current will change the actual V_OL.

To reduce the voltage drop over the switch, use a smaller current, i.e., use larger pull-up resistors (or better remove them, and use only the internal pull-ups).

0 Da-Wei Kuo over 1 year ago in reply to Clemens Ladisch

Prodigy 20 points

Hi Clemen

So in this case I should be looking at actual VoL instead of theoretical value right?

If the actual Vol is in spec it should be fine right?

0 Clemens Ladisch over 1 year ago in reply to Da-Wei Kuo

Guru 316760 points

Correct.

0 Jack Guan over 1 year ago in reply to Da-Wei Kuo

TI__Mastermind 40216 points

Hey Da-Wei,

Yes, the actual VOL of your application would be dependent on the VIL value into our device given under a certain VOL/IOL condition from the Device. You may also see TXS-EVM for further evaluation with the your system setup.

Regards,

Jack

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TXS0102DCUR and TXS0104EPWR logic levels SPECs concerns.