TXS0108E: Powe up sequence

Kazuhiko Hirano

Part Number: TXS0108E

Hello,

Q1
Datasheet 6.3 (3) says “VCCA must be less than or equal to VCCB”.
But, datasheet 6.1 says VCCA could be -0.5V to 4.6V and VCCB could be -0.5V to 6.5V.
So, power up sequence could be VCCA (1.8V) gets up first and then VCCB(3.3V) gets up with some delay?
Device is not damaged with this power up sequence?

Q2
If the above power up sequence is OK, my customer has a question about B port output voltage after VCCA (1.8V) gets up but before VCCB(3.3V) gets up.
OE is connected to VCCA. If A port input voltage is “low”, B port output voltage is also “low” after VCCA (1.8V) gets up but before VCCB(3.3V) gets up?

Best regards,

K.Hirano

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 243180 points

1. Staying inside the absolute maximum ratings prevents damage. Staying inside the recommended operating conditions guarantees that the device works correctly. When V_CCA > V_CCB, a current flows into V_CCA and out of V_CCB; See the Biasing Requirements for TXS, TXB, and LSF Auto-Bidirectional Translators application note.

2. That current might partially power up V_CCB. To ensure that all outputs are disabled, pull OE low.

0 Kazuhiko Hirano over 1 year ago in reply to Clemens Ladisch

TI__Genius 11613 points

Clemens,

Thank you for your responses.

For Q2, my customer is expecting B port output voltage is also “low” after VCCA (1.8V) gets up but before VCCB(3.3V) gets up.
Can they expect that 100% with EN = High?

Best regards,

K.Hirano

0 Clemens Ladisch over 1 year ago in reply to Kazuhiko Hirano

Guru 243180 points

Below 1.65 V, correct operation is not guaranteed; the output might be high or low.

0 Kazuhiko Hirano over 1 year ago in reply to Clemens Ladisch

TI__Genius 11613 points

Clemens,

Let me confirm a bit more.
Below 1.65V means VCCB is below 1.65V?
So, my customer's case, they can not expect B port output voltage is low, right?

Best regards,

K.Hirano

+1 Clemens Ladisch over 1 year ago in reply to Kazuhiko Hirano

Guru 243180 points

Correct.

OE should be connected to V_CCB.

Logic

Logic forum

TXS0108E: Powe up sequence