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Hello expert,
My customer is using SN74GTL2003 in their network card application, they got an issue that when they pullup 3.3V externally then the 1.8V signal will be always high and there is no function for the UART communication. May we know could we pullup 3.3V side(DREF) and there is no 1.8V(SREF) externally pullup but with the weak pullup from the chipset side(inside IC). We would like to know how can we put the pullup externally and get the right operation. Thanks a lot!
Best regards,
Ann Lien
Hi Clemens
Hers is the SCH
due to their confidential they can't provide total SCH.
The situation is they UART communication from CPU(1.8V) (marvell 7040 https://www.marvell.com/content/dam/marvell/en/public-collateral/embedded-processors/marvell-embedded-processors-armada-7040-product-brief-2017-12.pdf ) to chipset(3.3V) can't work. the mravell CPU have internal pull-high resistor.
1. 3.3V doesn't add pull-up resistor >>> only get 1.8V UART signal
2. 3.3V have pull-up resistor >> they have 3.3V output. but UART signal keep high both in 1.8V side and 3.3V side.
they have disconnect the remain chipset part so there is only connector now.
BRs
Brian
