SN75176B: CL

Hi Kengo,

1. There are no maximum capacity requirements for CL - most applications either do not have a discrete CL (as the transmission line typically adds capacitance ) and if it is used it typically is around 50pF  to help filter out higher frequency content. In reality there is a max capacitance that can be added, but this is going to be based on frequency content of signal and the length of the transmission line (higher capacitance is going to degrade max data rate and longer buses will also degrade max data-length) 

2. The wave will have a slower rise time across the load due the capacitor and it may not reach the maximum voltage due to higher frequencies being filtered out. Too large of a capacitor will change the load impedance of the system. For smaller capacitors this effect is small - for larger capacitors you will create an impedance mismatch between transmission line and load which will cause signal reflections which will further degrade signal integrity on the bus. We don't have a specific app note that covers this. 

Why does you/your customer want to use the load capacitance? Depending on why they want to use this may lead me to better solutions - because the load capacitance is typically not added and if it is - its generally a low value (pF range) 

Please let me know! 

Best,

Parker Dodson