MC33662LEF Datasheet, PDF (24/31 Pages) Freescale Semiconductor, Inc – LIN 2.1 / SAEJ2602-2, LIN Physical Layer

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
As described below and depicted in Figure 29 and
Table 7, the 33662L, 33662J, and 33662S have two
operational modes, Normal and Sleep. In addition, there are
two transitional modes: Awake mode and Preparation to
Sleep mode. The Awake mode allows the device to go into
Normal mode. The Preparation to Sleep mode allows the
device to go into Sleep mode.
NORMAL OR SLOW BAUD RATE
In the Normal mode, the LIN bus can transmit and receive
information.
The 33662L and 33662S (20 kbps) have a slew rate and
timing compatible with Normal Baud Rate and LIN protocol
specification 1.3, 2.0, and 2.1.
The 33662J (10 kbps) has a slew rate and timing
compatible with Low Baud Rate.
From Normal mode, the three devices can enter into Fast
Baud Rate (Toggle function).
FAST BAUD RATE
In Fast Baud Rate, the slew rate is around 10 times faster
than the Normal Baud Rate. This allows very fast data
transmission (> 100 kbps) -- for instance, for electronic
control unit (ECU) tests and microcontroller program
download. The bus pull-up resistor might be adjusted to
ensure a correct RC time constant in line with the high baud
rate used.
Fast Baud Rate is entered via a special sequence (called
toggle function) as follows:
1- EN pin set LOW while TXD is HIGH
2- TXD stays HIGH for 12.5 µs min
3- TXD set LOW for 12.5 µs min
4- TXD pulled HIGH for 12.5 µs min
5- EN pin set LOW to HIGH while TXD still HIGH
The device enters into the Fast Baud Rate if the delay
between Step 1 to Step 5 is 45 µs maximum. The toggle
function is described in Figures 22. Once in Fast Baud Rate,
the same toggle function just described previously is used to
bring the device back into Normal Baud Rate.
Fast Baud Rate selection is reported to the MCU by RXD
pin. Once the device enters in this Fast Baud Rate, the RXD
pin goes at low level for t₅. When the device returns in Normal
Baud Rate with the same toggle function, the RXD pin stays
high. Both sequences are illustrated in Figures 22 and 23.
PREPARATION TO SLEEP MODE
To enter the Preparation to Sleep mode, EN must be low
for a delay higher than t_LWUE.
If the WAKE pin state doesn’t change during t_SD and t_LWUE
then the 33662 goes into Sleep mode.
If the WAKE pin state changes during t_SD and if t_WF is
reached after end of t_SD then the device goes into Sleep
mode after the end of t_SD timing.
If the WAKE pin state changes during t_SD and t_WF delay
has been reached before the end of t_SD then the device goes
into Awake mode.
If the WAKE pin state changes before t_SD and the delay
t_WF ends during t_SD then the device goes into Awake mode.
If EN goes high for a delay higher than t_LWUE, the 33662
returns to Normal mode.
SLEEP MODE
To enter into Sleep mode, EN must be low for a delay
longer than t_SD and the Wake pin must stay in the same state
(High or Low) during this delay.
The device conditions to not enter in Sleep mode but enter
in Awake mode are detailed in the Preparation into Sleep
mode chapter. See Figure 26.
In Sleep mode, the transmission path is disabled and the
device is in Low Power mode. Supply current from V_SUP is
very low (6.0 µA typical value). Wake-up can occur from LIN
bus activity, from the EN pin and from the WAKE input pin. If
during the preparation to Sleep mode delay (t_SD), the LIN bus
goes low due to LIN network communication, the device still
enters into the Sleep mode. The device can be awakened by
a recessive to dominant start, followed by a dominant to
recessive state after t > t_WUF.
After a Wake-up event, the device enters into Awake
mode.
In the Sleep mode, the internal 725 kOhm pull-up resistor
is connected and the 30 kOhm is disconnected.
DEVICE POWER-UP (Awake Transitional Mode)
At power-up (V_SUP rises from zero), when V_SUP is above
the Power On Reset voltage, the device automatically
switches after a 160 µs delay time to the Awake transitional
mode. It switches the INH pin to a HIGH state and RXD to a
LOW state. See Figure 24.
DEVICE WAKE-UP EVENTS
The 33662L, 33662J, and 33662S can be awakened from
Sleep mode by three wake-up events:
• Remote wake-up via LIN bus activity
• Via the EN pin
• Toggling the WAKE pin
Remote Wake from LIN Bus (Awake Transitional Mode)
The device is awakened by a LIN dominant pulse longer
than t_WUF. Dominant pulse means: a recessive to dominant
transition, wait for t > t_WUF, then a dominant to recessive
33662
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Analog Integrated Circuit Device Data
Freescale Semiconductor