EVM for SN65HVD232 CAN Transceiver

Hi Govind,

Unfortunately, none of the 3.3V CAN transceivers in our portfolio have an EVM specifically made for them.

With that being said the SN65HVD257 EVM that you mentioned can easily be used for 3.3V CAN transceivers, but I think the SN65HVD255EVM would be the best suited, since the SN65HVD257 EVM is made for redundant networks and has additional logic devices populated on it.

http://www.ti.com/tool/SN65HVD255DEVM

On the SN65HVD255EVM, you could switch the U1 IC from the SN65HVD255 to one of the SN65HVD232. Since pin 5 and 8 are No Connect "NC" it doesn’t matter what position you leave the jumpers in.

Are you just looking for a 3.3V CAN transceiver without any modes? (no low power mode) We have other devices in the portfolio with different modes. This is our full family of 3.3V CAN trasnceivers:

Thanks,

John

Dear Mr. John,

Thanks a lot for your clear explanation. 

The additional features i copuld see in SN65HVD233/4/5 are Autobaud rate detection and Lookback Mode. But, i am not sure whether those features are required for my application or not. From data sheet i foud application areas as Device Net and Smart distribution systems. 

My Application is: We are developing a drive board for Elevator applications. 20 drive boards (20 CAN nodes) will be connected in the Bus. these 20 boards control the Motor drive boards. 

Couid ypu please help me in finding the appropriate transceivers??

Best Regards,

Govind.

Dear Mr. John,

Short and Specific questions Would be: 

1. Loopback for Diagnostic Functions and Loopback for autobaud function are specifically  for Device Net data buses .. ?? ?? what is the basic purpose of these pins.

2. Why the Vref pin (Vcc/2) is need to be connected to Split termination network?? What is basic function of this pin??

(I have worked on CAN circuit  used in power train application (automotive), i have not connected any reference voltage to split termination network)

Kindly clarify. These clarifications are required for me to select appropriate Tansceiver and EVM. 

Thanks & Regards,

Govind. 

Hi Govind,

The features that your system will need are very application dependent and I will not be able to tell you what will work best. I can however describe the features in a little more detail and you can see if they are of interest to you.

The loopback feature in the SN65HVD233, disables the driver for the CAN bus and the receiver from the bus. This feature is used for diagnostics to verify that the local TXD and RXD paths are working without any issues (rules out board faults). While in this mode messages cannot be transmitted to the bus or received from the bus.

The auto-baud feature on the SN65HVD235 is used for systems where module can be "hot-plugged" into a system that is operating and sending bus traffic where the module is not already programmed with a data rate of the system it is about to be plugged into. The idea is that the receive path from the bus to the RXD pin is fully active, and the TXD to RXD path within the transceiver is also active, but the TXD to bus drive path is set to inactive. This means that the node can receive traffic from the bus, but cannot send traffic onto the bus. The thing that makes this different than a simple silent mode, is that the TXD to RXD path is active and the node will see what it transmits to the bus without anyone on the bus seeing the traffic.

Therefore, when the module gets plugged into the system a startup routine can be written where the CAN controller will scan through a set of predefined data rates (let's say for this example that the available data rates are only 125KBPS, 250KBPS, 500KBPS and 1MBPS and the data rate on the bus is 250KBPS). The CAN controller would first start with the 125KBPS data rate and listen to the bus. I a message is transmitted on the bus and the node does not calculate the same CRC or receive a full frame because it is sampling too slowly, then it would calculate an error and attempt to send an error frame to the bus. Since the driver is turned off the error would not be transmitted to the bus, but the local controller would see the error frame and know that the data rate was not the correct, since it saw an error. The node would update its data rate to the next available data rate and wait for another message to be transited on the bus. The next data rate for this example is 250KBPS which happens to be the data rate on the bus. Therefore, the node would see a message on the bus, and calculate the same CRC that is being sent on the bus. Once receiving a correct frame the node would know if had the correct data rate chosen and could transition to normal mode. This entire routine could happen without the node ever interfering with the bus traffic.

In terms of VREF pin, it is a reference voltage output pin that is used to further stabilize the common mode point of the bus. If this is not something that you want and the device you select has this pin, you can either leave the pin floating our connect a capacitor to ground from it.

Thanks,

John

Hello John,

Thank you very much for clear explanation. I am going ahead with SN65HVD235/232 transceivers and SN65HVD255D EVM.

Thanks for your support.

Regards,

Govind.

Hello Mr. John,

I have decided to used SN65HVD232 transciver. While calculating the input current consumption of IC (To decide power supply current rating as i am using multiple ICs) i got few doubts.

As per data sheet, 

High-level output current, IOH  Driver =  -40mA & Reciver = - 8mA.

Low-level output current, IOL  Driver =  40mA & Reciver = -8mA.

Supply current Icc = 17mA Max.

So, maximum current from 3.3V supply = 48+8+17= 73mA Maximum.

Is this calculation method correct ..??

Kindly suggest.

Regards,

Govind.

Hi Govind,

The maximum 17-mA current is for both driver and receiver when un-loaded.  This means that is a good upper limit for the consumption during a recessive state (since the output driver will not need to source any current to establish a differential voltage).  For the dominant state, though, you also need to budget for the current that would flow through the load.  For a typical 60-Ohm load, the HVD232's maximum output voltage is 3 V.  This means that the driver must source an extra 50 mA to the load (3 V / 60 Ohms), making the overall current consumption in this state 17 mA + 50 mA = 67 mA.

When sizing a power supply, it is good practice to consider potential fault conditions as well.  For example, if there were a short on the HVD232's driver output its output current could be as high as 250 mA (i.e., the short-circuit output current spec).  This is much higher than the 50-mA you could expect under normal conditions.  If a power supply were not designed to be able to source this additional current, then this fault condition could cause the voltage rail to droop and potentially power off other components in the system sharing the same supply rail.

Best regards,
Max