Datasheet

75% SAMPLEPOINT

500 mVThreshold

900 mVThreshold

NOISEMARGIN

RECEIVERDETECTIONWINDOW

SN65HVD233-HT

SLLS933F –NOVEMBER 2008–REVISED AUGUST 2012

www.ti.com

Figure 27. Typical SN65HVD230 Differential Output Voltage Waveform

The CAN driver creates the difference voltage between CANH and CANL in the dominant state. The dominant

differential output of the SN65HVD230 is greater than 1.5 V and less than 3 V across a 60-Ω load. The minimum

required by ISO 11898 is 1.5 V and the maximum is 3 V. These are the same limiting values for 5-V supplied

CAN transceivers. The bus termination resistors drive the recessive bus state and not the CAN driver.

A CAN receiver is required to output a recessive state with less than 500 mV and a dominant state with more

than 900-mV difference voltage on its bus inputs. The CAN receiver must do this with common-mode input

voltages from –2 V to 7 V. The SN65HVD230 family receivers meet these same input specifications as 5-V

supplied receivers.

Common-Mode Signal

A common-mode signal is an average voltage of the two signal wires that the differential receiver rejects. The

common-mode signal comes from the CAN driver, ground noise, and coupled bus noise. Obviously, the supply

voltage of the CAN transceiver has nothing to do with noise. The SN65HVD230 family driver lowers the common-

mode output in a dominant bit by a couple hundred millivolts from that of most 5-V drivers. While this does not

fully comply with ISO 11898, this small variation in the driver common-mode output is rejected by differential

receivers and does not affect data, signal noise margins, or error rates.

Interoperability of 3.3-V CAN in 5-V CAN Systems

The 3.3-V–supplied SN65HVD23x family of CAN transceivers are electrically interchangeable with 5-V CAN

transceivers. The differential output is the same. The recessive common-mode output is the same. The dominant

common-mode output voltage is a couple hundred millivolts lower than 5-V–supplied drivers, while the receivers

exhibit identical specifications as 5-V devices.

Electrical interoperability does not assure interchangeability however. Most implementers of CAN buses

recognize that ISO 11898 does not sufficiently specify the electrical layer and that strict standard compliance

alone does not ensure interchangeability. This comes only with thorough equipment testing.

Bus Cable

ISO 11898 specifies a maximum bus length of 40 m and maximum stub length of 0.3 m with a maximum of 30

nodes. However, with careful design, users can have longer cables, longer stub lengths, and many more nodes

to a bus. A large number of nodes requires a transceiver with high input impedance, such as the SN65HVD233.

Product Folder Links: SN65HVD233-HT