MCP2003 datasheet(10/34 Pages) MICROCHIP

10 / 34 page

MCP2003/4/3A/4A

DS22230D-page 10

Fault condition or by an external drive. While the

transmitter is disabled, the internal 30 k

Ω pull-up

resistor on the LBUS pin is also disconnected to reduce

current.

TABLE 1-3:

FAULT/TXE TRUTH TABLE

1.5.5

TRANSMIT DATA INPUT (TXD)

The Transmit Data Input pin has an internal pull-up.

The LIN pin is low (dominant) when TXD is low, and high

(recessive) when TXD is high.

For extra bus security, TXD is internally forced to ‘1’

whenever the transmitter is disabled regardless of

external TXD voltage.

1.5.5.1

TXD Dominant Timeout

If TXD is driven low for longer than approximately 25

mS, the LBUS pin is switched to recessive mode and

the part enters TOFF Mode. This is to prevent the LIN

node from permanently driving the LIN Bus dominant.

The transmitter is reenabled on TXD rising edge.

1.5.6

GROUND (VSS)

This is the Ground pin.

1.5.7

LIN BUS (LBUS)

The bidirectional LIN Bus pin (LBUS) is controlled by the

TXD input. LBUS has a current limited open collector

output. To reduce EMI, the edges during the signal

changes are slope controlled and include corner

rounding control for both falling and rising edges.

The internal LIN receiver observes the activities on the

LIN bus, and matches the output signal RXD to follow

the state of the LBUS pin.

1.5.7.1

Bus Dominant Timer

The Bus Dominant Timer is an internal timer that

deactivates the LBUS transmitter after approximately

25 milliseconds of dominant state on the LBUS pin. The

timer is reset on any recessive LBUS state.

The LIN bus transmitter will be reenabled after a

recessive state on the LBUS pin as long as CS is high.

Disabling can be caused by the LIN bus being

externally held dominant, or by TXD being driven low.

Additionally, on the MCP2004/2004A, the FAULT pin

will be driven low to indicate the Transmitter Off state.

1.5.8

BATTERY (VBB)

This is the Battery Positive Supply Voltage pin.

1.5.9

VOLTAGE REGULATOR ENABLE

OUTPUT (VREN)

This is the External Voltage Regulator Enable pin.

Open source output is pulled high to VBB in all modes,

except Power-Down.

1.5.10

EXPOSED THERMAL PAD (EP)

Do not electrically connect, or connect to Vss.

Note:

The FAULT/TXE pin is true (‘0’) whenever

the internal circuits have detected a short

or thermal excursion and have disabled

the LBUS output driver.

TXD

RXD

Out

LINBUS

I/O

Thermal

Override

FAULT/TXE

Definition

External

Input

Driven

Output

VBB

OFF

FAULT, TXD driven low, LINBUS shorted to VBB

(Note 1)

VBB

OFF

GND

OFF

GND

OFF

OK, data is being received from the LINBUS

VBB

FAULT, Transceiver in thermal shutdown

VBB

NO FAULT, the CPU is commanding the

transceiver to turn off the transmitter driver

Legend: x = don’t care

Note 1:

The FAULT/TXE is valid after approximately 25 µs after TXD falling edge. This is to eliminate false fault

reporting during bus propagation delays.

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