AN1075

Migrating Designs from MCP201 to MCP2021-500
Author:
Chuck Simmers
Microchip Technology Inc.
DEVICE MIGRATIONS
The original MCP201 LIN (Local Interconnect Network)
transceiver was designed to comply with LIN 1.2 and
1.3 physical layer specifications The MCP2021-500 is
designed to be pin- and functionally-compatible with
the earlier MCP201, and to meet the latest LIN 2.0 and
2.1 specifications. For most applications, the
MCP2021-500 can be dropped in place of a MCP201
in an existing design without printed circuit board or
firmware modifications.
Note:
The MCP2021/2/3/4 family of devices
support both LIN and K-line (ISO-9141)
buses, 5.0V and 3.3V system voltages,
and a new RESET output. The MCP2021500 is the drop-in replacement for the
MCP201.
down function. If the TXE function is not required, this
pin may be left floating. Refer to Section 1.3.5 or the
“MCP202x LIN Transceiver” data sheet, DS22018, for
more information on the TXE function.
The FAULT output definition is the same. Bus
contention detect has been debounced.
Voltage Regulator
There is no longer a need for input filter capacitor to be
8-10 times larger than output load capacitor In fact they
can both be 1.0 µF and the regulator will be stable over
the whole temperature range if the output capacitor has
a couple ohms of ESR. Quiescent current of the
regulator is, typically, 20% that of the MCP201 With
transmitter off, this drops an additional 10 µA. Output
voltage is 4.85V to 5.15V from 6.5V to 18V over full
load range and temperature range. Time to VREG ready
after POR is less than 400 µs instead of 2.5 ms. Thermal shutdown temperature is 165°C.
The following are some considerations to be made
when evaluating the upgrade to MCP2021-500.
All of the turn on points and turn off points are the same.
VREG turns on between 5.5V and 6V on VBAT and shuts
down when VBAT is 4V.
HARDWARE DIFFERENCES
SOFTWARE DIFFERENCES
The only difference exists on two pins of the MCP2021500.
The internal state-machine of the MCP2021-500 has
been simplified. The device will enter the ‘Operational’
as soon as the VREG output has stabilsed and CS/
LWAKE and FAULT/TXE are both high (‘1’). No low-tohigh edge is necessary.
CS/LWAKE
The CS/LWAKE input is now level sensitive rather than
edge-triggered. A low-to-high transition is no longer
necessary to enter the ‘Operational’ mode on powerup, or to toggle CS/LWAKE to clear a fault condition.
Any existing firmware that implements toggling will
work in a MCP2021-500 without modification.
FAULT/TXE
On the MCP201, this pin was designated FAULT/
SLPS. During power-on this pin was sampled to select
between fast and slow voltage slope rate control. This
function is not required in the MCP2021-500 due to its
time-based slew-rate waveshaping. The Transmit
Enable (TXE) function has taken its place.
REFERENCES
MCP201 Data Sheet, “LIN Transceiver with Voltage
Regulator”, DS21730
MCP202X Data Sheet, “LIN Transceiver with Voltage
Regulator”, DS22018
Note:
For additional information, please contact
your Microchip Automotive Products
Representative.
Existing designs that utilized this function with a
external pull-up or pull-down resistor, need to remove
the resistor. The pin should be routed to a microcontroller port pin to take advantage of the new TXE power-
© 2007 Microchip Technology Inc.
DS01075A-page 1
NOTES:
DS01075A-page 2
© 2007 Microchip Technology Inc.
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DS01075A-page 3
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DS01075A-page 4
© 2007 Microchip Technology Inc.
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