MCP2021_12 Datasheet, PDF (5/52 Pages) Microchip Technology – LIN Transceiver with Voltage Regulator

1.0 DEVICE OVERVIEW
The MCP2021/2/1P/2P provides a physical interface
between a microcontroller and a LIN half-duplex bus. It
is intended for automotive and industrial applications
with serial bus speeds up to 20 Kbaud.
The MCP2021/2/1P/2P provides a half-duplex, bidirec-
tional communications interface between a microcon-
troller and the serial network bus. This device will
translate the CMOS/TTL logic levels to LIN-level logic,
and vice versa.
The LIN specification 2.0 requires that the trans-
ceiver(s) of all nodes in the system be connected via
the LIN pin, referenced to ground, and with a maximum
external termination resistance load of 510Ω from LIN
bus to battery supply. The 510Ω corresponds to 1 Mas-
ter and 16 Slave nodes.
The MCP2021/2/1P/2P-500 provides a +5V, 50 mA,
regulated power output. The regulator uses an LDO
design, is short-circuit protected, and will turn the
regulator output off if it falls below 3.5V.
The MCP2021/2/1P/2P also includes thermal-
shutdown protection.
The regulator is specifically designed to operate in the
automotive environment and will survive +43V load
dump transients, double-battery jumps, and reverse
battery connections when a reverse blocking diode is
used. The other members of the MCP2021/2/1P/2P-
330 family output +3.3V at 50 mA with a turn-off voltage
of 2.5V. (See Section 1.6 “Internal Voltage
Regulator”).
MCP2021/2 wakes from Power-Down mode on a
dominant level on LBUS. MCP2021P/2P wakes at a
transition from recessive level to dominant level on
LBUS.
1.1 Optional External Protection
1.1.1 REVERSE BATTERY PROTECTION
An external reverse-battery-blocking diode should be
used to provide polarity protection (see Figure 1-6).
1.1.2
TRANSIENT VOLTAGE
PROTECTION (LOAD DUMP)
An external 43V transient suppressor (TVS) diode,
between VBB and ground, with a 50Ω transient protec-
tion resistor (RTP) in series with the battery supply and
the VBB pin protect the device from power transients
(see Figure 1-6) and ESD events. While this protection
is optional, it is considered good engineering practice.
The resistor value is chosen according to Equation 1-1.
MCP2021/2/1P/2P
EQUATION 1-1:
RTP <= (VBBmin - 5.5) / 250 mA.
5.5V = VUVLO + 1.0V,
250 mA is the peak current at Power-On when
VBB = 5.5V
1.2 Internal Protection
1.2.1 ESD PROTECTION
For component-level ESD ratings, please refer to the
Section 2.1 “Absolute Maximum Ratings†”.
1.2.2 GROUND LOSS PROTECTION
The LIN Bus specification states that the LIN pin must
transition to the recessive state when ground is discon-
nected. Therefore, a loss of ground effectively forces
the LIN line to a hi-impedance level.
1.2.3 THERMAL PROTECTION
The thermal protection circuit monitors the die temper-
ature and is able to shut down the LIN transmitter and
voltage regulator if it detects a thermal overload.
There are three causes for a thermal overload. A ther-
mal shut down can be triggered by any one, or a com-
bination of, the following thermal overload conditions:
• Voltage regulator overload
• LIN bus output overload
• Increase in die temperature due to increase in
environmental temperature
Driving the TXD and checking the RXD pin makes it
possible to determine whether there is a bus contention
(i.e., Rx = low, Tx = high) or a thermal overload condi-
tion (i.e., Rx = high, Tx = low).
© 2005-2012 Microchip Technology Inc.
DS22018F-page 5