TCAN330 Datasheet, PDF (22/39 Pages) Texas Instruments – CAN Transceivers

TCAN330, TCAN332, TCAN334, TCAN337
TCAN330G, TCAN332G, TCAN334G, TCAN337G
SLLSEQ7A – DECEMBER 2015 – REVISED JANUARY 2016
www.ti.com
10.4 Device Functional Modes
10.4.1 CAN Bus States
The CAN bus has two logical states during operation: recessive and dominant. See Figure 31 and Figure 32.
Recessive bus state is when the high resistive internal input resistors of each node's receiver bias the bus to a
common mode of about 1.85 V across the bus termination resistors. Recessive is equivalent to logic high and is
typically a differential voltage on the bus of about 0 V. Recessive state is also the idle state.
Dominant bus state is when the bus is driven differentially by one or more drivers. Current is induced to flow
through the termination resistors and generate a differential voltage on the bus. Dominant is equivalent to logic
low and is a differential voltage on the bus greater than the minimum threshold for a CAN dominant. A dominant
state overwrites the recessive state.
During arbitration, multiple CAN nodes may transmit a dominant bit at the same time. In this case the differential
voltage of the bus will be greater than the differential voltage of a single driver.
The host microprocessor of the CAN node will use the TXD terminal to drive the bus and will receive data from
the bus on the RXD pin.
Transceivers with low power Standby Mode have a third bus state where the bus terminals are weakly biased to
ground via the high resistance internal resistors of the receiver. See Figure 31 and Figure 32.
Normal and Silent Modes
Standby and Shutdown
Modes
CANH
Vdiff
Vdiff
CANL
CANH
1.85 V _A
Bias
Unit
B
CANL
RXD
Recessive
Dominant
Recessive
Figure 31. Bus States (Physical Bit
Representation)
Time, t
A. Normal and Silent Modes
B. Standby and Shutdown Modes
Figure 32. Simplified Recessive Common Mode
Bias Unit and Receiver
The devices have four main operating modes:
1. Normal mode (all devices)
2. Silent mode (TCAN330, TCAN337)
3. Standby mode with wake (TCAN334)
4. Shutdown mode (TCAN330, TCAN334)
Table 3. CAN Transceivers with Silent Mode
S
HIGH
LOW/NC
Device MODE
Reduced Power Silent
(Listen) Mode
Normal Mode
DRIVER
Disabled (OFF)⁽¹⁾
Enabled (ON)
RECEIVER
Enabled (ON)
Enabled (ON)
(1) See Figure 31 for bus state.
(2) Mirrors bus state: low if CAN bus is dominant, high if CAN bus is recessive.
RXD PIN
Mirrors Bus State⁽²⁾
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