MCP2021/2/1P/2P
DS22018F-page 6
2005-2012 Microchip Technology Inc.
FIGURE 1-1:
Thermal Shutdown State Diagrams.
1.3
Modes of Operation
For an overview of all operational modes, please refer
1.3.1
POWER-ON RESET MODE
Upon application of VBB, the device enters Power-on
Reset mode (POR). During this mode, the part main-
tains the digital section in a Reset mode and waits until
the voltage on pin VBB rises above the “ON” threshold
(Typ. 5.75V) to enter to the Ready mode. If during the
operation, the voltage on pin VBB falls below the “OFF”
threshold (Typ. 4.25V), the part comes back to the POR
mode.
1.3.2
POWER-DOWN MODE
In the Power-Down mode, the transmitter and the
voltage regulator are off. Only the receiver wake-up
from LIN bus section, and the CS/LWAKE pin wake-up
circuits are in operation. This is the lowest power mode.
If pin CS/LWAKE goes to a high level during Power-
Down mode, the device immediately enters Ready
mode and enables the voltage regulator; and after the
output has stabilized (approximately 0.3 ms to 1.2 ms),
the device goes to Operation mode or Transmitter-Off
for MCP2021P/2P).
LIN bus activity will also change the device from
Power-Down mode to Ready mode. MCP2021/2
wakes up on dominant level of LIN bus, and
MCP2021P/2P on a falling edge that follows a domi-
nant level lasting 20 s of time.
The Power-Down mode can be reached through either
Operation mode or Transmitter-Off mode.
1.3.3
READY MODE
Upon entering Ready mode, the voltage regulator and
receiver-threshold-detect circuit are powered up. The
transmitter remains in off state. The device is ready to
receive data as soon as the regulator is stabilized, but
not to transmit. If a microcontroller is being driven by
the voltage regulator output, it will go through a POR
and initialization sequence. The LIN pin is in the reces-
sive state for MCP2021/2 and in floating state for
MCP2021P/2P.
The device will stay in Ready mode until the output of
the voltage regulator has stabilized and the CS/LWAKE
pin is true (‘1’). After VREG is stable and CS/LWAKE is
high, MCP2021/2 will enter Operation mode; and
MCP2021P/2P will enter either Operation mode or
Transmitter-Off mode, depending on the level of the
1.3.4
OPERATION MODE
In this mode, all internal modules are operational.
The device will go into the Power-Down mode on the
falling edge of CS/LWAKE.
For the MCP2021P/2P devices, the pull-up resistor is
switched on only in this mode.
Operation
Mode
Transmitter
Shutdown
LIN Bus
Voltage
Shutdown
Regulator
Output
Temperature <SHUTDOWNTEMP
Overload
to VBB
Overload
Temperature <SHUTDOWNTEMP
Note:
The above time interval <1.2 ms assumes
12V VBB input and no thermal shutdown
event.