MLX80020 Datasheet, PDF (16/26 Pages) Melexis Microelectronic Systems – Enhanced LIN Transceiver

MLX80020
Enhanced LIN Transceiver
4.4 Sleep Mode
The most power saving mode of the MLX80020 is the sleep mode. The MLX80020 offers two procedures to
enter the sleep mode:
 The mode is selected when the pin EN is driven LOW in normal mode for longer than the specified
filter time (t_{EN_deb}). The mode change into sleep mode is possible even in case of dominant voltage
levels on the LIN bus, pins WAKE or TxD.
 If the MLX80020 is in standby mode after power-on or wake-up, a sleep counter is started and
switches the transceiver into sleep mode after the specified time (typ. 350ms) even when the
microcontroller of the ECU will not confirm the normal operation by setting the EN pin to logic HIGH.
This new feature allows faulty blocked LIN nodes to reach always the most power saving mode.
Being in sleep mode the INH pin becomes floating and the ECU voltage regulator can be switched off in
order to minimize the current consumption of the complete LIN node. The transmitter is disabled and the pin
RxD is disconnected from the receive path and is floating. The slave termination resistor (LIN pull up resistor
with decoupling diode between pins LIN and Vs) is disconnected and only a weak LIN pull up resistor is
applied to the LIN bus (see chapter 5.4 fail-safe features)
4.5 Wake Up
When in sleep mode the MLX80020 offers thee wake-up procedures:
 In applications with continuously powered ECU a wake up via mode transition to normal mode is
possible (see chapter 4.3 Normal Mode)
 Remote wake-up via LIN bus traffic
After a falling edge on the LIN bus followed by a dominant voltage level for longer than the specified
value(t_{wu_remote}) and a rising edge on pin LIN will cause a remote wake up (see fig.4 page )
 Local wake-up via a negative edge on pin WAKE
A negative edge on the pin WAKE and a dominant voltage level for longer than the specified
time(t_{wu_local}) will cause a local wake-up. The current for an external switch has to be provided by an
external pull up resistor R_WK. For a reverse current limitation in case of a closed external switch and
a negative ground shift or an ECU loss of ground a protection resistor R_{WK_prot} between pin WAKE
and the switch is recommended. (see fig.5 page )
The pin WAKE provides a weak pull up current towards the battery voltage that provides a HIGH
level on the pin in case of open circuit failures or if no local wake up is required. In such applications
it is recommended to connect the pin WAKE directly to pin Vs in order to prevent influences due to
EMI.
4.6 Wake Up Source Recognition
The device can distinguish between a local wake-up event (pin WAKE) and a remote wake-up event. The
wake-up source flag is set after a local wake-up event and is indicated by an active LOW on pin TxD.
The wake-up flag can be read if an external pull up resistor towards the microcontroller supply voltage has
been added (see fig.5 ) and the MLX80020 is still in stanby mode:
 LOW level indicates a local wake-up event
 HIGH level indicates a remote wake up event
The wake-up request is indicated by an active LOW on pin RxD and can be used for an interrupt..
When the microcontroller confirms a normal mode operation by setting the pin EN to HIGH, both the wake-up
request on pin RxD as well as the wake-up source flag on pin TxD are reset immediately.
MLX80020 – Datasheet
3901080020
Page 16 of 26
November 2015
Rev 006