SN74AVC4T774: #OE pin with 1.8V directly input

Kay Chen53

Part Number: SN74AVC4T774
Other Parts Discussed in Thread: TS3A5223,

Hi there:

I'd like to check our customer application for SN74AVC4T774, the schematic as attached. TS3A5223 as a switch to control the SN74AVC4T774

about the #OE (PCIe_SPI_OE) this signal will connect to 1.8V voltage level directly when EEC_SG_EN pull Hi level.

Is that OK with this connection?

over 6 years ago

0 Kay Chen53 over 6 years ago

Expert 2225 points

update application for switch/router application

0 ShreyasRao over 6 years ago in reply to Kay Chen53

TI__Guru 58600 points

hi Kay,

It is not going to damage the device if connected directly to supply or cause any malfunctions/ reliability issues.
As long as the switch from low to high and high to low can be made to control the DIR, this is fine.

0 Kay Chen53 over 6 years ago in reply to ShreyasRao

Expert 2225 points

Hi Shreyas

Thanks, update the application schematic from customer, would that be the same as mention before?

0 ShreyasRao over 6 years ago in reply to Kay Chen53

TI__Guru 58600 points

Dont think anything changed from what was existing previously.

I do not see concerns on this configuration connecting the OE signal with a pullup resistance to the device.

0 Hsieh Andy over 6 years ago in reply to ShreyasRao

Prodigy 20 points

i am Accton RD Andy, my qusetion as below.

In the SN74AVC4T774 Datasheet, it is stated that the OE pin needs a pullup resistor, but it does not mention that it can be directly connected to the VCC.

That is, when TS3A5223RSWR SEL pin is low, TS3A5223RSWR Pin3 is connected to Pin5 (1.8V), while TS3A5223RSWR Pin3 is connected to SN74AVC4T774 OE pin.

This will damage SN74AVC4T774 OE pin damage?

0 ShreyasRao over 6 years ago in reply to Hsieh Andy

TI__Guru 58600 points

hi Hsieh,

OE pin is CMOS input device and hence will not consume current into or out of the pin more than the leakage current listed on the datasheet.
The OE pin wont be damaged during normal operation.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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SN74AVC4T774: #OE pin with 1.8V directly input