MCP2003 datasheet(9/32 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS22230A-page 9

MCP2003/4

TABLE 1-2:

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 longer than approximately 10 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 re-enabled on the 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 deac-

tivates

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 re-enabled after a

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

Disabling can be caused by the LIN bus being exter-

nally held dominant, or by TXD being driven low. Addi-

tionally, on the MCP2004, 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.

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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