Datasheet

 2010-2013 Microchip Technology Inc. DS20002230E-page 11
MCP2003/4/3A/4A
1.5.10 EXPOSED THERMAL PAD (EP)
Do not electrically connect, or connect to Vss.
1.6 MCP2003/4 and MCP2003A/4A
Difference Details
The differences between the MCP2003/4 and the
MCP2003/4A devices are isolated to the wake-up func-
tionality. The changes were implemented to make the
device more robust to LIN bus conditions, outside of
the normal operating conditions. The MCP2003/4 will
wake-up from Power Down mode during any LIN falling
edge held low longer than 20 µs.
In the case where a LIN system is designed to minimize
stand-by current by disconnecting all bus pull-ups
resistors (including the external master pull-up resistor
to V
BB), the original MCP2003/4 could wake up, if the
floating bus drifted to a valid low level. The MCP2003/
4A revisions were modified to require a rising edge
after a valid low level. This will prevent an undesired
system wake-up in this scenario, while maintaining
functional capability with the original version.
It should be noted that the original MCP2003/4 meets
all LIN transceiver specification requirements and mod-
ules can be designed to pass all LIN system require-
ments. However, when all bus pull-up resistors are
disconnected, the MCP2003/4 requires the module
designer to write firmware to monitor the LIN Bus after
any wake-up event to prevent the transceiver from
automatically transitioning from Ready mode to Opera-
tional mode.
If the MCP2003/4 is placed into Operational mode, V
BB
to LBUS pull-up resistor is automatically connected,
which will raise the LIN bus to a recessive level; then
putting the device to Power-Down mode may cause
L
BUS to be floating, and thus wake up all bus nodes. To
prevent this, the designer should ensure
TXD(MCP2003) or TXE(MCP2004) is held low until valid
bus activity is verified (see Figure 1-6). This will ensure
the transceiver transitions from Ready mode to Trans-
mitter Off mode, until bus activity can be verified.
In the case of valid bus activity, the transceiver can shift
to Operation mode, while if there is no bus activity, the
device can be again placed into Power Down. The
design practices needed to accomplish this are fully
detailed in Tech Brief TB3067 - “MCP2003 Power-
Down Mode and Wake-Up Handling in Case of LIN
Bus Loss” (DS93067).
The revised MCP2003/4A devices now eliminate the
need for firmware to prevent system wide wake-up.
The revised devices now require a longer valid bus low
(see updated t
BDB value in Section 2.3 “DC Specifi-
cations” and Figure 2-7), which enables a rising edge
detect circuit. The device will now only wake up after a
rising edge, following a low longer than t
BDB. While the
module designer can still hold T
XD (MCP2003) or
T
XE(MCP2004) low during wake-up, to enter Transmit-
ter Off mode from Ready mode, it is not required to pre-
vent an advertent system wake-up.
In addition to the longer t
BDB value, the time from wake-
up detect to V
REN enable is shortened as documented
in Section 2.3 “DC Specifications”.
FIGURE 1-6: MCP2003/2004 SWITCHING TIMING DIAGRAM FOR THE FORCED POWER-
DOWN MODE SEQUENCE
TXD
V
REN
CS
Ready
Mode
Transmitter OFF
Mode
Power Down
Mode after Master
Sleep instruction
Power Down
Mode
tTx2CS >= 100ns
tCSactive >= 100µs
TXD to 0
forced
externally
TXD state depending
on how the Slave
Microcontroller is
powered
LBUS
State
LIN bus
disconnected