
2012 Microchip Technology Inc.
DS22298A-page 3
MCP2021A/2A
1.0
FUNCTION DESCRIPTION
The MCP2021A/2A provides a physical interface
between a microcontroller and a LIN half-duplex bus. It
is intended for automotive and industrial applications
with serial bus baud rates up to 20 Kbaud. This device
will translate the CMOS/TTL logic levels to LIN logic
levels, and vice versa. The device offers optimum EMI
and ESD performance; it can withstand high voltage on
the LIN bus. The device supports two low-power
modes to meet automotive industry power consump-
tion requirements. The MCP2021A/2A also provides a
+5V or 3.3V 70 mA regulated power output.
1.1
Modes of Operation
The MCP2021A/2A works in five modes: POWER-ON-
RESET mode, POWER-DOWN mode, READY mode,
OPERATION mode, and TRANSMITTER OFF mode.
For an overview of all operational modes, please refer
to
Table 1-1. For the operational mode transition,
FIGURE 1-1:
STATE DIAGRAM
1.1.1
POWER-ON-RESET MODE
Upon application of VBB, or whenever the voltage on
VBB is below the threshold of regulator turn off voltage
VOFF (typically 4.50V), the device enters POWER-ON-
RESET mode (POR). During this mode, the device
maintains the digital section in a reset mode and waits
until the voltage on VBB pin rises above the threshold of
regulator turn on voltage VON (typically 5.75V) to enter
to the READY mode. In POWER-ON-RESET mode,
the LIN physical layer and voltage regulator are dis-
abled, and RESET output (MCP2022A only) is forced
to LOW.
POR
(2)
VREG OFF
RX OFF
TX OFF
READY
VREG ON
RX ON
TX OFF
TX OFF
VREG ON
RX ON
TX OFF
POWER-DOWN
VREG OFF
RX OFF
TX OFF
OPERATION
VREG ON
RX ON
TX ON
VBB>VON
CS/LWAKE=1&
FAULT/TXE=0&
VREG_OK=1
(1)
CS/LWAKE=0
CS/LWAKE=1 &
FAULT/TXE=1
(3) &
TXD=1&
VREG_OK=1
(1)
CS/LWAKE=1&
FAULT/TXE=1
(3)&
TXD=1
CS/LWAKE=1&
FAULT/TXE=0
CS/LWAKE=0
CS/LWAKE=1 OR
Voltage Rising Edge on LBUS
CS/LWAKE=0
Note 1: VREG_OK : Regulator Output Voltage > 0.8VREG_NOM.
2: If the voltage on pin VBB falls below VOFF, the device will enter POWER ON RESET mode from all other
modes, which is not shown in the figure.
3: FAULT/TXE = 1 represents input high and no fault conditions. FAULT/TXE = 0 represents input low or a