Other Parts Discussed in Thread: SN65HVD96, THVD8000
My questions relate to the TIDA-01171 AC-coupled rs-485 reference design.
We are considering this or a similar solution for a rs-485 design requiring isolation between a 'master' Head Unit and the 'slave' Sensors. The series capacitors used in this reference design could provide the necessary isolation with the overall design still allowing for rs-485 communications.
The reference design presents two nodes, but can this topology be extended to cater for many nodes ? Our situation will always include one Head Unit, but the number of Sensors will vary depending on the customer requirement. The reference is with a 120R terminating resistor at each node, but how are terminating resistors managed with multiple nodes ? Is it still with one such 120R resistor at the two ends ? If so then how are capacitor values calculated when only two nodes are with a terminating resistor while others are without ? Or should a non-120R resistor be used with each node with the series capacitor chosen based on that resistance value ?
The reference schematic shows 1nF series capacitors on each node. How was the capacitance value calculated ? In general how is each series capacitor value calculated when there can be a variable number of nodes ? And what baud-rate is 1nF suitable for ? Our rs-485 comms is currently operating at 19,200 baud.
Can you provide design guidelines in addition to the information already included with TIDA-01171 that would aid in calculating component values in a multi-node system taking into account terminating resistors and baud-rate ? Actually, are terminating resistors required ?
Another question relates to the "SymPol" SN65HVD96 Transceiver which is integral to this solution. Unfortunately in our application we cannot choose VCC of 5V, which is the recommended for this IC, so is there an alternate to this IC that can operate from 3.3Vdc or lower ?
I also note the following information on your website "A fully assembled board has been developed for testing and performance validation only, and is not available for sale.". Is it possible to acquire these dev kits, and if so how ?
Thank-you.
