MCP2021-330E-P MICROCHIP [Microchip Technology], MCP2021-330E-P Datasheet - Page 7

• Manufacturer Part Number: MCP2021-330E-P
• Description: LIN Transceiver with Voltage Regulator
• Manufacturer: MICROCHIP [Microchip Technology]

1.3.5
Whenever the FAULT/TXE signal is low, or permanent
dominant on TXD/LBUS is detected, the L
transmitter is off.
The transmitter may be re-enabled whenever the
FAULT/TXE signal returns high, either by removing the
internal fault condition or when the CPU returning the
FAULT/TXE high. The transmitter will not be enabled if
the FAULT/TXE pin is brought high when the internal
fault is still present.
If TX-OFF mode is caused by TXD/LBUS permanent
dominant level, the transmitter can recover when the
permanent dominant status disappears.
The transmitter is also turned off whenever the voltage
regulator is unstable or recovering from a fault. This
prevents unwanted disruption of the bus during times of
uncertain operation.
1.3.6
The Wake-Up sub-module observes the L
to detect bus activity. Bus activity is detected when the
voltage on the L
imately 0.4V
The MCP2021/2 device is level sensitive to L
inant level longer than 20 µs will cause the device to
leave the Power-Down mode. The MCP2021P/2P
device is falling-edge sensitive to L
transition from recessive to dominant followed by at
least 20 µs dominant level can wake up the device.
Putting CS/LWAKE to high level also wakes up the
device. Refer to
1.3.7
The MCP202xP is a minor variation of the MCP202x
device that adds improved state machine control as
well as the ability to disconnect the internal 30kΩ pull-
up between LIN and VBB in all modes except normal
operation. These changes allow the system designer
to better handle fault conditions and reduce the overall
system current consumption. The differences between
the two device versions are as follows:
1.
2.
© 2005-2012 Microchip Technology Inc.
Switchable LIN-VBB Pull-Up Resistor:
On the MCP202xP device, the internal 30kΩ
pull-up resistor is disconnected in all modes
except Operation Mode. On the MCP202x
device, this pull-up resistor is always connected.
(See the
MCP2021P/2P Block Diagram
Power Down Wake-up on LIN Traffic:
The MCP202xP device requires a LIN falling
edge to generate a valid Wake condition due to
bus traffic. The MCP202x device will generate a
Wake anytime LIN is at a valid dominant level.
TRANSMITTER-OFF MODE
WAKE-UP
DIFFERENCE DETAILS BETWEEN
MCP2021/2 AND MCP2021P/2P
BB
MCP2021/2 Block Diagram
for at least a typical duration of 20 µs.
BUS
Figure 1-2
stays below a threshold of approx-
and
Figure
BUS
for details.)
1-3.
. Only the L
BUS
BUS
and the
in order
. Dom-
BUS
BUS
3.
To properly take advantage of the device differences
will require the system designer to implement some
microcontroller code to the power-up routine. This code
will monitor the status of the LIN bus to determine how
the dominant signal should be responded to. It will also
determine if the local LIN node needs to respond or can
‘Listen Only’. If the local LIN node does not need to
respond, it can enter Transmitter Off Mode, disconnect-
ing the 30kΩ pull-up, reducing module current while still
maintaining the ability to properly receive all valid LIN
messages.
Note:
Because of this, if the LIN bus becomes perma-
nently shorted, it becomes impossible to place
the MCP202x in a low power state.
State Machine Options:
The MCP202xP device is able to enter Trans-
mitter Off Mode from Ready Mode without tran-
sitioning
MCP202x device must enter Operation Mode
from Ready Mode. (See State Machine Dia-
grams,
This capability allows the system designer to
monitor the bus in Ready Mode to determine if
the system should transition to normal operation
and connect the internal pull-up or if Ready
Mode was reached due to an invalid condition.
In the case of an invalid condition, the
MCP202xP device can be placed into Power
Down mode without connecting the internal pull-
up and waking other nodes on the LIN Bus net-
work.
MCP2021/2/1P/2P
To enter Transmitter Off, the system must
set TXE ‘low’ before pulling CS high (see
Figure 1-5). Otherwise, if CS is pulled high
first, the MCP202xP will enter Operation
Mode due to the internal pull-up on TXE.
Figure 1-2
through
and
Operation
Figure 1-3
DS22018F-page 7
Mode.
for details).
The