TCAN1042-Q1_17 Datasheet, PDF (18/40 Pages) Texas Instruments – Automotive Fault Protected CAN Transceiver with CAN FD

TCAN1042-Q1, TCAN1042V-Q1, TCAN1042H-Q1
TCAN1042HV-Q1, TCAN1042G-Q1, TCAN1042GV-Q1
TCAN1042HG-Q1, TCAN1042HGV-Q1
SLLSES9B – FEBRUARY 2016 – REVISED MAY 2017
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Feature Description (continued)
9.3.3 Undervoltage Lockout
The supply terminals have undervoltage detection that places the device in protected mode. This protects the
bus during an undervoltage event on either the V_CC or V_IO supply terminals.
Table 2. Undervoltage Lockout 5 V Only Devices (Devices without the "V" Suffix)⁽¹⁾
V_CC
> UV_VCC
< UV_VCC
DEVICE STATE
Normal
Protected
BUS OUTPUT
Per TXD
High Impedance
(1) See the V_IT section of the Electrical Characteristics.
(2) Mirrors bus state: low if CAN bus is dominant, high if CAN bus is recessive.
RXD
Mirrors Bus⁽²⁾
High Impedance
Table 3. Undervoltage Lockout I/O Level Shifting Devices (Devices with the "V" Suffix)
V_CC
> UV_VCC
< UV_VCC
> UV_VCC
< UV_VCC
V_IO
> UV_VIO
> UV_VIO
< UV_VIO
< UV_VIO
DEVICE STATE
Normal
STB = High: Standby Mode
STB =Low: Protected Mode
Protected
Protected
BUS OUTPUT
Per TXD
Recessive
High Impedance
High Impedance
High Impedance
RXD
Mirrors Bus⁽¹⁾
Bus Wake RXD Request⁽²⁾
High (Recessive)
High Impedance
High Impedance
(1) Mirrors bus state: low if CAN bus is dominant, high if CAN bus is recessive.
(2) Refer to Remote Wake Request via Wake Up Pattern (WUP) in Standby Mode
NOTE
After an undervoltage condition is cleared and the supplies have returned to valid levels,
the device typically resumes normal operation within 50 µs.
9.3.4 Unpowered Device
The device is designed to be 'ideal passive' or 'no load' to the CAN bus if it is unpowered. The bus terminals
(CANH, CANL) have extremely low leakage currents when the device is unpowered to avoid loading down the
bus. This is critical if some nodes of the network are unpowered while the rest of the of network remains in
operation. The logic terminals also have extremely low leakage currents when the device is unpowered to avoid
loading down other circuits that may remain powered.
9.3.5 Floating Terminals
These devices have internal pull ups on critical terminals to place the device into known states if the terminals
float. The TXD terminal is pulled up to V_CC or V_IO to force a recessive input level if the terminal floats. The
terminal is also pulled up to force the device into low power Standby mode if the terminal floats.
9.3.6 CAN Bus Short Circuit Current Limiting
The device has two protection features that limit the short circuit current when a CAN bus line is short-circuit fault
condition: driver current limiting (both dominant and recessive states) and TXD dominant state time out to
prevent permanent higher short circuit current of the dominant state during a system fault. During CAN
communication the bus switches between dominant and recessive states, thus the short circuit current may be
viewed either as the instantaneous current during each bus state or as an average current of the two states. For
system current (power supply) and power considerations in the termination resistors and common-mode choke
ratings, use the average short circuit current. Determine the ratio of dominant and recessive bits by the data in
the CAN frame plus the following factors of the protocol and PHY that force either recessive or dominant at
certain times:
• Control fields with set bits
• Bit stuffing
• Interframe space
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