MCP2003B datasheet(7/32 Pages) MICROCHIP

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 2015-2016 Microchip Technology Inc.

DS20005463C-page 7

MCP2003B

1.5

Pin Descriptions

1.5.1

RECEIVE DATA OUTPUT (RXD)

The Receive Data Output pin is an open-drain (OD)

output and follows the state of the LIN pin, except in

Power-Down mode.

1.5.1.1

RXD Monitoring

The RXD pin is internally monitored. It has to be at a

high level (> 2.5V typical) while LBUS is recessive in

Operation mode. Otherwise, an internal fault will be

created and the device will transition to Transmitter Off

mode.

1.5.2

CHIP SELECT (CS)

This is the Chip Select Input pin. An internal pull-down

resistor will keep the CS pin low. This is done to ensure

that no disruptive data will be present on the bus while

the microcontroller is executing a Power-on Reset and

an I/O initialization sequence. The pin must detect a

high level to activate the transmitter. An internal Low-

Pass filter, with a typical time constant of 10 µs,

prevents unwanted wake-up (or transition to Power-

Down mode) on glitches.

If CS = 0 when the VBB supply is turned on, the device

goes to Ready mode as soon as internal voltages sta-

bilize, and stays there as long as the CS pin is held low

(0). In Ready mode, the receiver is on and the LIN

transmitter driver is off.

If CS = 1 when the VBB supply is turned on, the device

will proceed to Operation mode, or TXOFF (refer to

Figure 1-2), as soon as internal voltages stabilize.

This pin may also be used as a local wake-up input

(refer to Example 1-1). In this implementation, the

microcontroller I/O controlling the CS should be

converted to a high-impedance input allowing the

internal pull-down resistor to keep CS low. An external

switch, or other source, can then wake-up both the

transceiver and the microcontroller (if powered). Refer

to Section 1.3 “Modes of Operation”, for detailed

operation of CS.

1.5.3

WAKE-UP INPUT (WAKE)

The WAKE pin has an internal 800 kΩ pull-up to VBB.

A falling edge on the WAKE pin causes the device to

wake from Power-Down mode. Upon waking, the

MCP2003B will enter Ready mode.

1.5.4

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.

TABLE 1-2:

PINOUT DESCRIPTIONS

Pin Name

8-Lead

SOIC

2x3 DFN

3x3 DFN

Normal Operation

RXD

Receive Data Output (OD), HV tolerant

Chip Select (TTL), HV tolerant

WAKE

Wake-up, HV tolerant

TXD

Transmit Data Input (TTL), HV tolerant

VSS

Ground

LBUS

LIN Bus (bidirectional)

VBB

Battery Positive

VREN

Voltage Regulator Enable Output

—

Exposed Thermal Pad. Do not electrically

connect or connect to Vss.

Legend: TTL = TTL Input Buffer; OD = Open-Drain Output

Note:

A voltage regulator sensing circuit is

connected to RXD. This sensing circuit

internally monitors the RXD pin when

LBUS is recessive (RXD = 1). It will not

allow the device to switch (or stay) in

Operation Mode if the RXD pin is left

open. The RXD pin must be connected to

a valid supply through a pull-up resistor as

RXD is an open drain pin.

Note:

It is not recommended to tie CS high, as

this can result in the device entering

Operation

mode

before

the

microcontroller is initialized and may

result in unintentional LIN traffic. The CS

pin is internally pulled down to ground with

190 k

 when CS is less than VIL, and

 when CS is greater than VIH. The

current on CS is limited to about 2 µA

when CS is greater than VIH.

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