TXS0104E: uart level shift from 3.3V to 1.8V

Hey Lanjie,

lanjie Liu103016 said:

②B2、B3input 1.8V,A2、A3 output 3.3V

Based on what you said here, you may have distortion or stray voltages. This part requires that during operation, Vcca is less than or equal to Vccb. The I/O pins of A (A1-A4) must be at the same potential as Vcca and B1 - B4 must be at the Vccb potential. If I am understanding the list of info that you included than you are violating this rule. 

As for the data rate, are you just transmitting one bit per symbol or are you using some other kind of signaling technique? I'd assume it's just a binary transmission, with that assumption then your data rate is 115200bps or .115Mbps. The max data rate for open-drain is 2Mbps and for push-pull it is 24Mbps. Both of these rates are well above what you need and this part should have no problems for your UART application.

To answer your question about better devices, the TXB could be a better option. Both parts can handle the data rates you seek with little issue, the key distinction I would make between them is power consumption. Due to the construction of the TXS architecture, it has internal 10K resistors that will always be drawing current, in your scenario it will be approximately 510 uA. The TXB design uses buffers however and has little to no standby current draw. This architecture change comes at the expense of max load capacitance however, TXB needs to have low (<70pF) loads, while the TXS can drive higher (>70pF). One exception to this is if you have low data rates (which you do) the load capacitance can be increased slightly for both parts since that requirement is for signal integrity at the max data rate.

I would recommend switching to the TXB0104 for the power conservation reasons above unless you have high line / load capacitance.

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Best Regards,

Nick