TCAN1042-Q1 Datasheet, PDF (16/32 Pages) Texas Instruments – Automotive Fault Protected CAN Tranceiver

TCAN1042-Q1, TCAN1042V-Q1, TCAN1042H-Q1
TCAN1042HV-Q1, TCAN1042G-Q1, TCAN1042GV-Q1
TCAN1042HG-Q1, TCAN1042HGV-Q1
SLLSES9 – FEBRUARY 2016
www.ti.com
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
GOOD
BAD
DEVICE STATE
Normal
Protected
BUS OUTPUT
Per Device State and TXD
High Impedance
RXD
Mirrors Bus
High Impedance (3-state)
(1) See the V_IT section of the Electrical Characteristics.
Table 3. Undervoltage Lockout I/O Level Shifting Devices (Devices with the "V" Suffix)
V_CC
GOOD
BAD
GOOD
BAD
V_IO
GOOD
GOOD
BAD
BAD
DEVICE STATE
Normal
Protected
Protected
Protected
BUS OUTPUT
Per STB and TXD
High Impedance
Recessive
High Impedance
RXD
Mirrors Bus
High (Recessive)
High Impedance (3-state)
High Impedance (3-state)
NOTE
After an undervoltage condition is cleared and the supplies have returned to valid levels,
the device typically resumes normal operation within 300 µs.
9.3.4 Unpowered Device
The device is designed to be an '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 so they will not load 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 STB
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 several protection features that limit the short circuit current when a CAN bus line is shorted.
These include driver current limiting (dominant and recessive). The device has 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 with the data and control fields bits,
thus the short circuit current may be viewed either as the instantaneous current during each bus state, or as a
DC average current. 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
• TXD dominant time out (fault case limiting)
These ensure a minimum recessive amount of time on the bus even if the data field contains a high percentage
of dominant bits.
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TCAN1042GV-Q1 TCAN1042HG-Q1 TCAN1042HGV-Q1