MLX80020 Datasheet, PDF (18/26 Pages) Melexis Microelectronic Systems – Enhanced LIN Transceiver

MLX80020
Enhanced LIN Transceiver
5. Fail-safe features
5.1 Loss of battery
If the ECU is disconnected from the battery, the bus pin is in high impedance state. There is no impact to the
bus traffic and to the ECU itself. Reverse current is limited to < 20µA
5.2 Loss of Ground
In case of an interrupted ECU ground connection there is no influence to the bus line. The current from the
ECU to the LIN bus is limited by the weak pull up resistance of the pin LIN, the slave termination resistor is
disconnected in order to fulfill the SAE J2602 requirements for the loss of ground current (<100µA @12V).
5.3 Short circuit to battery
The transmitter output current is limited to the specified value in case of short circuit to battery in order to
prevent high current densities and thermal hot spots in the LIN driver.
5.4 Short circuit to ground
If the LIN bus wiring is shorted to negative shifted ground levels, there is no current flow from the ECU
ground to the bus and no distortion of the bus traffic occurs.
The permanent failure current from battery to ground can be reduced dramatically by using the INH pin as
termination control pin for the master pull up resistor (See Figure 7: Application Circuitry).
If the controller detects a short circuit of the LIN bus to ground the transceiver can be set into sleep mode.
The INH pin is floating and therefore the master pull up resistor is disconnected from the bus line.
Additionally the internal slave termination resistor is switched off and only a weak pull up termination is
applied to the LIN bus (typ. 75A). If the failure disappears, the bus level will become recessive again and
will wake up the system even if no local wake up occurs or is possible.
5.5 Thermal overload
The MLX80020 is protected against thermal overloads. If the chip temperature exceeds the specified value,
the transmitter is disabled until thermal recovery and the following recessive to dominant transition on pin
TxD. The receiver is still working while thermal shutdown.
5.6 Undervoltage lock out
If the battery supply voltage is missing or decreased under the specified value(V_{S_UV}), the transmitter is
disabled to prevent undefined bus traffic.
5.7 Open Circuit protection
 The pin TxD provides a weak pull down. The transmitter can not be enabled.
 The pin EN provides a weak pull down to prevent undefined normal mode transitions.
 If the battery supply voltage is disconnected, the pin RxD is floating
 The pin WAKE provides a weak pull up current towards supply voltage Vs to prevent local wake-up
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MLX80020 – Datasheet
3901080020
Page 18 of 26
November 2015
Rev 006