MCP201
1.2
Internal Protection
1.0
DEVICE OVERVIEW
The MCP201 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.
1.2.1
ESD PROTECTION
For component-level ESD ratings, please refer to the
maximum operation specifications.
The MCP201 provides a half-duplex, bidirectional
communications interface between a microcontroller
and the serial network bus. This device will translate
the CMOS/TTL logic levels to LIN level logic, and vice
versa.
1.2.2
GROUND LOSS PROTECTION
The LIN bus specification states that the LIN pin must
transition to the recessive state when ground is
disconnected. Therefore, a loss of ground effectively
forces the LIN line to a hi-impedance level.
The LIN specification 1.3 requires that the transceiver
of all nodes in the system be connected via the LIN pin,
referenced to ground and with a maximum external
termination resistance of 510Ω from LIN bus to battery
supply. The 510Ω corresponds to 1 Master and 16
Slave nodes.
1.2.3
THERMAL PROTECTION
The thermal protection circuit monitors the die
temperature and is able to shut down the LIN
transmitter and voltage regulator. Refer to Table 1-1 for
details.
The MCP201 provides a +5V 50 mA regulated power
output. The regulator uses a LDO design, is short-
circuit-protected and will turn the regulator output off if
it falls below 3.5V. The MCP201 also includes thermal
shutdown protection. The regulator has been specifi-
cally designed to operate in the automotive environ-
ment and will survive reverse battery connections,
+40V load dump transients and double-battery jumps
(see Section 1.6 “Internal Voltage Regulator”).
There are three causes for a thermal overload. A
thermal shut down can be triggered by any one, or a
combination of, the following thermal overload
conditions.
• Voltage regulator overload
• LIN bus output overload
• Increase in die temperature due to increase in
environment temperature
Driving the TXD and checking the RXD pin makes it
possible to determine whether there is a bus contention
(Rx = low, Tx = high) or a thermal overload condition
(Rx = high, Tx = low).
1.1
Optional External Protection
1.1.1
TRANSIENT VOLTAGE
PROTECTION (LOAD DUMP)
Note:
After recovering from a thermal, bus or
voltage regulator overload condition, the
device will be in the Ready1 mode. In order
to go into Operational mode, the CS/
WAKE pin has to be toggled.
An external 27V transient suppressor (TVS) diode,
between VBAT and ground, with a 50Ω resistor in series
with the battery supply and the VBAT pin, serves to pro-
tect the device from power transients (see Figure 1-2)
and ESD events. While this protection is optional, it
should be considered as good engineering practice.
1.1.2
REVERSE BATTERY PROTECTION
An external reverse-battery-blocking diode can be
used to provide polarity protection (see Figure 1-2).
This protection is optional, but should be considered as
good engineering practice.
TABLE 1-1:
SOURCES OF THERMAL OVERLOAD(1,2)
TXD
RXD
Comments
L
H
LIN transmitter shutdown, receiver and voltage regulator active, thermal overload
condition.
H
L
Regulator shutdown, receiver active, bus contention.
Legend: x = Don’t care, L = Low, H = High
Note 1: LIN transceiver overload current on the LIN pin is 200 mA.
2: Voltage regulator overload current on voltage regulator greater than 50 mA.
© 2007 Microchip Technology Inc.
DS21730F-page 3
MICROCHIP [ MICROCHIP ]
