TCAN330_16 Datasheet, PDF (29/40 Pages) Texas Instruments – 3.3-V CAN Transceivers with CAN FD (Flexible Data Rate)

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TCAN330, TCAN332, TCAN334, TCAN337
TCAN330G, TCAN332G, TCAN334G, TCAN337G
SLLSEQ7D – DECEMBER 2015 – REVISED APRIL 2016
System Examples (continued)
11.3.2 Differential Signal
CAN is a differential bus where complementary signals are sent over two wires and the voltage difference
between the two wires defines the logical state of the bus. The differential CAN receiver monitors this voltage
difference and outputs the bus state with a single ended logic level output signal.
RECEIVER DETECTION WINDOW
NOISE MARGIN
75% SAMPLE POINT
NOISE MARGIN
900 mV Threshold
500 mV Threshold
Figure 39. Typical Differential Output Waveform
The CAN driver creates the differential voltage between CANH and CANL in the dominant state. The dominant
differential output of the TCAN33x is greater than 1.5 V and less than 3 V across a 60-Ω load as defined by the
ISO11898 standard. 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 when less than 500 mV of differential voltage exists on the
bus, and a dominant state when more than 900 mV of differential voltage exists on the bus. The CAN receiver
must do this with common-mode input voltages from –2 V to 7 V. The TCAN33x family receivers meet these
same input specifications as 5 V supplied receivers.
11.3.3 Common-Mode Signal and EMC Performance
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. Since the bias voltage
of the recessive state of the device is dependent on V_CC, any noise present or variation of V_CC has an effect on
this bias voltage seen by the bus. The TCAN33x family has the recessive bias voltage set higher than 0.5 x V_CC
to match common mode in recessive mode to dominant mode. This results in superior EMC performance.
12 Power Supply Recommendations
To ensure reliable operation at all data rates and supply voltages, each supply should be decoupled with a 100-
nF ceramic capacitor located as close to the V_CC supply pins as possible. The TPS76333 is a linear voltage
regulator suitable for the 3.3 V supply.
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