Pull-up and Pull-down for #OE of SN74LVC8T245DBR

prasanna kumara G

Dear team,

We are using SN74LVC8T245DBR in our design,

When i go through the datasheet it says "

To ensure the high-impedance state during power up or power down, OE should be tied to VCC through a pullup
resistor"

If we pull down #OE to low permanently(without pull-up), What will happen to output during power up and power down.

Let me know if there is problem if we pull down #OE to low permanently as below

Is there any functionality issue if we connect OEn pin to low( pulled low) permanently.

Is there any damages to IC if we do like above circuit and what will be the output during powering ON or Powering OFF of IC,

Regards,
Prasanna G

over 7 years ago

0 aozer over 7 years ago

TI__Mastermind 23895 points

Hello Prasanna,

OE needs to be pulled high and should not be permanently pulled low. It is recommended to do this to allow proper isolation during power up or power down to prevent any damage to your devices. If you leave OE permanently pulled low there will be no isolation between the two ports.

0 prasanna kumara G over 7 years ago in reply to aozer

Expert 1585 points

Hello,

May i know how the device will get damage if we pull OE permanently to ground. Here device means SN74LVC8T245DBR or device connected to this IC.

Regards,
Prasanna G

0 Nirav Patel over 7 years ago in reply to prasanna kumara G

TI__Expert 6335 points

Prasanna,

I believe that Adrian was reffering to other devices connected to the translator, not the translator itself. You can see this E2E post for more details:

Best Regards,
Nirav

Logic

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Pull-up and Pull-down for #OE of SN74LVC8T245DBR