NCV7382
http://onsemi.com
9
Functional Description
Initialization
After power on, the chip automatically enters the
V
BAT
-standby mode. In this intermediate mode the INH
output will become HIGH (V
S
) and therefore the ECU -
voltage regulator will provide the V
CC
-supply. The
transceiver will remain in the V
BAT
standby mode until the
controller sets it to normal operation (EN = High). Bus
communication is only possible in normal mode. The
NCV7382 switches itself to the V
BAT
-standby mode if V
CC
is missing or below the undervoltage lockout threshold.
Operating Modes
The EN pin is used to switch the NCV7382 into different
operating modes.
Normal Mode
All of the NCV7382 is active. Switching to normal mode
can only be done with EN = high.
Sleep Mode
The sleep mode (EN = LOW) can only be reached from
normal mode and permits a very low power consumption
because the transceiver and the external voltage regulator
are disabled. If V
CC
has been switched off, a wakeup
request from the bus line (remote wakeup) will cause the
NCV7382 to enter the V
BAT
-standby mode (V
CC
is present
again) and sets the RxD output to low until the device enters
the normal operation mode (active LOW interrupt at RxD).
If the INH pin is not connected to the regulator or the
inhibitable external regulator is not the one that provides
the V
CC
- supply, the normal mode is directly accessible by
logic high on the EN pin. (Wakeup via mode change/local
wakeup.)
In order to prevent an unintended wakeup caused by
disturbances in the automotive environment, incoming
dominant signals from the bus have to exceed the wakeup
delay time.
Thermal Shutdown Mode
If the junction temperature T
J
is higher than 155°C, the
NCV7382 could be switched into the thermal shutdown
mode. Transmitter will be switched off.
If T
J
falls below the thermal shutdown temperature (typ.
140°C), the NCV7382 will be switched to the previous
state.
Table 1. Mode Control
EN V
CC
Comment INH RxD
0 0 V
BAT
-standby, Power On Vs 0
0 1 V
BAT
-standby, V
CC
On Vs X
1 1 Normal Mode Vs V
CC
= Recessive
0 = Dominant
0 0 Sleep Mode Floating 0
0 1 Sleep Mode
Regulator not disabled
Directly switch to normal mode with EN = 1
Floating V
CC
0 0/1 Remote wakeup request Vs 0 - Active low wakeup
interrupt
LIN BUS Transceiver
The transceiver consists of a bus-driver (1.2 V @
40 mA) with slew rate control, current limit, and a receiver
with a high voltage comparator with filter circuitry.
BUS Input/Output
The recessive BUS level is generated from the integrated
30 k pullup resistor in series with a diode. The diode
prevents the reverse current on V
BUS
when V
BUS
> V
S
.
No additional termination resistor is necessary to use the
NCV7382 on LIN slave nodes. If this IC is used for LIN
master nodes, it is necessary to terminate the bus with
an external 1.0 kW resistor in series with a diode to V
BAT
or INH (See Section Short Circuit to Ground).
TxD Input
During transmission the signal on TxD will be
transferred to the BUS driver for generating a BUS signal.
To minimize the electromagnetic emission of the bus line,
the BUS driver has integrated slew rate control and wave
shaping.
Transmitting will be interrupted in the following cases:
• Sleep Mode
• Thermal Shutdown
• V
BAT
-standby
The CMOS compatible input TxD directly controls the
BUS level:
TxD = low → BUS = low (dominant level)
TxD = high → BUS = high (recessive level)
