THVD1500: Logic input capacitance

Hi Shaofeng,

We don't specify input pin capacitance on this device, or most of  our RS-485 transceivers. The input capacitance won't be very large and should be less than 10pF (10pF is probably high). This is a standard TTL input so the capacitance isn't going to be extremely large. 

Generally speaking any pull-up or pull-down resistors are going to be between 1K and 10K - our typical application schematic in datasheet for this device uses 10k. The pin leakage is going to be +/-5uA - but typically hovers right around 0uA - so only a few mV worst case offset with 1k to 10k resistors.  Essentially you can just put 10K resistors as pull-ups and pull-downs on this device and it is very unlikely there would be a problem unless your customers driver input circuit adds a lot of capacitance and/or they are driving the input with an open collector/open drain type driver (not suggested ) its just usually not an issue for sizing resistors. Since they want a pull-down they aren't driving the inputs with open drain/collector drivers so 10k should be fine. 

Best,

Parker Dodson