TXB0302: Test mode, only weak pullups driving both sides of TXB0302

ron Hall

Part Number: TXB0302

Circuit has a test mode where both sides of TXB0302 are tri-stated. 20K+ pullup on 3.3V side, 25K + pulldown on 2.5V side. 2nd data path has 40K and 20K pullups. I presume the output state of the TB0302 is indeterminate since none of the cases meet the sink/source requirements to force device to known state, which is OK in this mode. It appears these use cases will cause increased power dissipation within the IC. Is this continuous current / dissipation enough to cause damage to the device(output driver), assuming office ambient temperatures?

5 months ago

0 Jack Guan 5 months ago

TI__Mastermind 25431 points

Hey Ron,

The TXB0302 has internal 1k series resistance at the I/Os that are actively being driven at all times. Having external pullups will form a voltage divider resulting in lower VOH and heightened VOL values as shown in page 6 of the d/s and in Effects of pullup and pulldown resistors on TXS and TXB devices.

In any case, this will not cause damage to the device where the abs max cont. output current is 50mA:

Regards,

Jack

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TXB0302: Test mode, only weak pullups driving both sides of TXB0302