MCP2021/2
LIN Transceiver with Voltage Regulator
Features
• The MCP2021 and MCP2022 are compliant with
LIN Bus Specifications 1.3, 2.0, and 2.1 and are
compliant to SAE J2602
• Support Baud Rates up to 20 Kbaud with
LIN-compatible output driver
• 43V load dump protected
• Very low EMI meets stringent OEM requirements
• Wide supply voltage, 6.0V - 18.0V continuous:
- Maximum input voltage of 30V
• Extended Temperature Range: -40 to +125°C
• Interface to PIC EUSART and standard USARTs
• Local Interconnect Network (LIN) bus pin:
- Internal pull-up resistor and diode
- Protected against ground shorts
- Protected against loss of ground
- High current drive
• Automatic thermal shutdown
• On-Board Voltage Regulator:
- Output voltage of 5.0V with tolerances of
±3% overtemperature range
- Available with alternate output voltage of
3.3V with tolerances of ±3% overtemperature
range
- Maximum continuous input voltage of 30V
- Internal thermal overload protection
- Internal short circuit current limit
- External components limited to filter
capacitor only and load capacitor
• Two low-power modes:
- Receiver on, Transmitter off, voltage
regulator on (
≅
85 µA)
- Receiver monitoring bus, Transmitter off,
voltage regulator off (
≅
16 µA)
Description
The MCP2021/2 provides a bidirectional, half-duplex
communication physical interface to automotive, and
industrial LIN systems to meet the LIN bus specification
Revision 2.0. The device incorporates a voltage
regulator with 5V @ 50 mA or 3.3V @ 50 mA regulated
power supply output. The regulator is short circuit
protected, and is protected by an internal thermal shut-
down circuit. The regulator has been specifically
designed to operate in the automotive environment and
will survive reverse battery connections, +43V load
dump transients, and double-battery jumps. The device
has been designed to meet the stringent quiescent
current requirements of the automotive industry.
MCP2021/2 family members:
• 8-pin PDIP, DFN and SOIC packages:
- MCP2021-330, LIN-compatible driver,
8-pin, 3.3V regulator
- MCP2021-500, LIN-compatible driver,
8-pin, 5.0V regulator
• 14-lead PDIP, TSSOP and SOIC packages with
RESET output:
- MCP2022-330, LIN-compatible driver,
14-pin, 3.3V regulator
- MCP2022-500, LIN-compatible driver,
14-pin, 5.0V regulator
Package Types
DFN-8, PDIP-8, SOIC-8
MCP2021
RXD
CS/LWAKE
V
REG
TXD
1
2
3
4
8
7
6
5
FAULT/TXE
V
BB
L
BUS
V
SS
PDIP-14, SOIC-14, TSSOP-14
RXD
CS/LWAKE
V
REG
TXD
RESET
NC
NC
1
2
14
13
FAULT/TXE
V
BB
L
BUS
V
SS
NC
NC
NC
MCP2022
3
4
5
6
7
12
11
10
9
8
©
2009 Microchip Technology Inc.
DS22018E-page 1
MCP2021/2
Block Diagram
Short Circuit
Protection
Thermal
Protection
RESET
Voltage
Regulator
V
BB
Ratiometric
Reference
Wake-Up
Logic and
Power Control
V
REG
Internal Circuits
RXD
~30 kΩ
CS/LWAKE
TXD
FAULT/TXE
Thermal
Protection
Short Circuit
Protection
OC
L
BUS
V
SS
DS22018E-page 2
©
2009 Microchip Technology Inc.
MCP2021/2
1.0
DEVICE OVERVIEW
1.2
1.2.1
Internal Protection
ESD PROTECTION
The MCP2021/2 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 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.
The LIN specification 2.0 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.
The MCP2021-500 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 MCP2021/2 also includes
thermal shutdown protection. The regulator has been
specifically designed to operate in the automotive
environment and will survive reverse battery connec-
tions, +43V load dump transients and double-battery
jumps. The other members of the MCP2021-330 family
output +3.3V at 50 mA with a turn-off voltage of 2.5V.
(see
Section 1.6 “Internal Voltage Regulator”).
For component-level ESD ratings, please refer to the
maximum operation specifications.
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.
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.
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
1.1.1
Optional External Protection
REVERSE BATTERY PROTECTION
FIGURE 1-1:
An external reverse-battery-blocking diode should be
used to provide polarity protection (see Example 1-1).
THERMAL SHUTDOWN
STATE DIAGRAMS
Output
Overload
LIN bus
shorted
to V
BB
Operation
Mode
Transmitter
Shutdown
1.1.2
TRANSIENT VOLTAGE
PROTECTION (LOAD DUMP)
An external 43V transient suppressor (TVS) diode,
between V
BB
and ground, with a 50Ω transient
protection resistor (R
TP
) in series with the battery
supply and the V
BB
pin serve to protect the device from
power transients (see
Example 1-1)
and ESD events.
While this protection is optional, it should be
considered as good engineering practice.
Voltage
Regulator
Shutdown
Temp <
SHUTDOWNTEMP
Temp <
SHUTDOWN
TEMP
EQUATION 1-1:
R
TP
<= (V
BBmin
- 5.5) / 250 mA.
5.5V = V
UVLO
+ 1.0V,
250 mA is the peak current at power-on when
V
BB
= 5.5V
©
2009 Microchip Technology Inc.
DS22018E-page 3
MCP2021/2
1.3
Modes of Operation
1.3.4
OPERATION MODE
For an overview of all operational modes, please refer
to
Table 1-1.
In this mode, all internal modules are operational.
The MCP2021/2 will go into the Power-down mode on
the falling edge of CS/LWAKE.
1.3.1
POWER-ON-RESET MODE
Upon application of V
BB
, the device enters Power-On-
Reset mode (POR). During this mode, the part
maintains the digital section in a reset mode and waits
until the voltage on pin V
BB
rises above the “ON”
threshold (Typ. 5.75V) to enter to the Ready mode. If
during the operation, the voltage on pin V
BB
falls below
the “OFF” threshold (Typ. 4.25V), the part comes back
to the Power-On-Reset mode.
1.3.5
TRANSMITTER OFF MODE
Whenever the FAULT/TXE signal is low and the L
BUS
transmitter is off.
The transmitter may be re-enabled whenever the
FAULT/TXE signal returns high, either by removing the
internal fault condition or 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.
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.
1.3.2
POWER-DOWN MODE
In the Power-down mode, the transmitter and the
voltage regulator are both off. Only the receiver
section, and the CS/LWAKE pin wake-up circuits are in
operation. This is the lowest power mode.
If any bus activity (e.g. a BREAK character) or CS/
LWAKE going to a high level should occur during
Power-down mode, the device will immediately enter
the Ready mode, enable the voltage regulator, and
once the output has stabilized (approximately 0.3 ms to
1.2 ms), go to the Operation mode.
Note:
The above time interval < 1.2 ms assumes
12V V
BB
input and no thermal shutdown
event.
1.3.5.1
Wake-up
The Wake-up sub module observes the L
BUS
in order
to detect bus activity. Bus activity is detected when the
voltage on the L
BUS
stays below a threshold of
approximately 3V for at least a typical duration of 10 µs.
Such a condition causes the device to leave the Power-
down mode.
FIGURE 1-2:
CS/LWAKE
= false
The part will also enter the Ready mode, followed by
the Operation mode, if the CS/LWAKE pin should
become active true (‘1’).
The part may only enter the Power-down mode after
going through an Operation mode step.
OPERATIONAL MODES
STATE DIAGRAMS
Power-down
Mode
Bus Activity
OR
CS/LWAKE = true
1.3.3
READY MODE
Upon entering the Ready mode, the voltage regulator
and receiver threshold detect circuit are powered up.
The transmitter remains in power down mode. The
device is ready to receive data but not to transmit. If a
microcontroller is being driven by the voltage regulator
output, it will go through a Power-on Reset and initial-
ization sequence. The LIN pin is in the recessive state.
The device will stay in the Ready mode until the output
of the voltage regulator has stabilized and CS/LWAKE
pin is true (‘1’). After V
REG
is OK and CS/LWAKE pin is
true, the transmitter is enabled and the part enters the
Operation mode.
On Power-on of the V
BB
supply pin, the component will
stay in the Ready mode if CS/LWAKE is low. If CS/
LWAKE is high, the device will immediately enter the
Operation mode.
Transmitter
Off
Mode
FAULT/TXE
= false
CS/LWAKE
= false
Operation
Mode
Ready
Mode
V
BB
OK = true
FAULT/TXE = true
V
REG
OK = true
AND
CS/LWAKE = true
Start
POR
Note:
While the MCP2021/2 is in shutdown, T
XD
should not be actively driven high or it may
power internal logic through the ESD
diodes and may damage the device.
DS22018E-page 4
©
2009 Microchip Technology Inc.
MCP2021/2
TABLE 1-1:
State
POR
READY
OPERATION
OVERVIEW OF OPERATIONAL MODES
Transmitter
OFF
OFF
ON
Receiver
OFF
Activity
Detect
ON
Voltage
Regulator
OFF
ON
ON
Operation
Read CS/LWAKE, if LOW, then READY,
if HIGH, Operational mode
If CS/LWAKE high level, then Operation
mode
Bus Off state
Comments
If CS/LWAKE low level, then Power down Normal
If FAULT/TXE low level, then Transmitter- Operation
Off mode
mode
On LIN bus falling, go to READY mode.
On CS/LWAKE high level, go to
Operational mode
If CS/LWAKE low level, then Power down
If FAULT/TXE high, then Operation mode
Low Power
mode
POWER DOWN
OFF
Activity
Detect
ON
OFF
TRANSMITTER-
OFF
OFF
ON
1.4
Typical Applications
TYPICAL MCP2021 APPLICATION
+12
+12
EXAMPLE 1-1:
WAKE-UP
43V
(5)
220 kΩ
V
DD
TXD
RXD
I/O
I/O
(3)
R
TP
(5)
C
F
Master Node Only
+12
C
G
V
REG
TXD
V
BB
1 kΩ
RXD
CS/LWAKE
FAULT/TXE
V
SS
L
BUS
27V
(4)
LIN Bus
100nF
Note 1:
See
Figure 2-3
for correct capacity and ESR for stable operation.
.
2:
C
F
is the filter capacitor for the external voltage supply.
3:
This diode is only needed if CS/LWAKE is connected to 12V supply.
4:
Transient suppressor diode. Vclamp L = 43V.
5:
These components are required for additional load dump protection above 43V..
©
2009 Microchip Technology Inc.
DS22018E-page 5
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