
MC33399
Automotive “Local Interconnect Network” Physical Interface
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6
Device Wake-up Events
The device can be waked up from sleep mode from three
wake-up events:
- LIN bus activity
- Internal node wake-up described below (EN pin).
- Wake up from Wake pin
Fig 5, 6, 7, 8 and 9 show device application circuit and
detail of wake up operations.
Wake-up From LIN Bus
A wake-up from LIN pin switched from recessive state to
dominant (switch from Vsup to GND) can occur. This is
achieved by a node sending a wake-up frame on the bus.
This condition will internally wake-up the interface, which will
switch high the INH pin to enable the voltage regulator.The
device will switch into the “wait for normal mode”. The
microcontroller and the complete application will be powered
up. The microcontroller will have to switch the EN pin to a
high level to allow the device to leave the “wait for normal
mode” and turn it into “normal mode” in order to allow
communication on the bus.
Wake-up From Internal Node Activity
The application can internally wake-up. In this case the
micro controller of the application will set the device enable
pin in the high state. The device will switch into ”normal
mode”.
Wake-up From Wake Pin
The application can wake up with the activation of an
external switch. Refer to pin description.
Mode of Operation
The device has two main modes of operation:
Normal Mode
This is the normal transmitting and receiving mode. All
features are available.
Sleep Mode
In this mode the transmission path is disabled and the
device is in low power mode. Supply current from Vsup is
20uA typical. Wake-up can occur from LIN bus activity, from
node internal wake-up through the EN pin and from Wake
input pin.
Device Power Up
At system power up (Vsup rises from zero) the device
automatically switches into the “wait for normal mode”. It
switches the INH pin in high state to Vsup level. The
microcontroller of the application will then confirm the normal
mode by setting the EN pin high.
Special Automotive Requirements
ESD
The LIN pin has high Human Body Model ESD immunity
and handle more than +-4kV.
Electromagnetic Compatibility
Emission on LIN Bus Output Line
Emission level on LIN bus output is internally limited and
reduced by active slew rate control of the output bus driver.
Susceptibility
On the LIN bus pin: The device offers high susceptibility
immunity level from external disturbance occurring at the LIN
bus pin in order to guarantee communication during external
disturbance. On the Wake input pin:an internal filter is
implemented to reduce the false wake up during external
disturbance.
Noise Filtering
Noise filtering is used to protect the electronic module
against illegal wake-up spikes on the bus. Integrated receiver
filters suppress any HF noise induced into the bus wires. The
cut-off frequency of these filters is a compromise between
propagation delay and HF suppression.
Figure 4. Device State Machine
Normal Mode
INH: high (INH HS switch ON)
Communication: ON
Wait Normal Mode
INH: high (INH internal High
Side switch ON)
Communication: OFF
EN = 1
Sleep Mode
INH: high impedance (INH HS switch
OFF)
Communication: OFF
EN = 0
Local wake-up event
System Unpowered, VBAT = 0
A : VBAT >7V
B : VBAT <7V
C : Bus wake up event
D : Wake up from Wake switch
A
B
C
EN = 1
B
B
Go to sleep command
D
F
Freescale Semiconductor, Inc.
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