NCV7425

http://onsemi.com

5

Table 4. MODE SELECTION

Mode

RxD

INH

LIN

Transceiver

30 kW on LIN

RSTN

Normal −

Slope (Note 3)

ON

Low = Dominant State

High = Recessive State

High if STB = High

during state transition;

Floating otherwise

Normal Slope

ON

High

Normal − Low

Slope (Note 4)

ON

Low = Dominant State

High = Recessive State

High if STB = High

during state transition;

Floating otherwise

Low Slope

ON

High

Stand−by

(Note 5)

ON

Low after LIN

wake−up, high

otherwise (Note 6)

Floating

OFF

OFF

under−voltage

monitor

Sleep

OFF

(Note 6)

Floating

OFF

OFF

Low

3. The normal slope mode is entered when pin EN goes HIGH while TxD is in HIGH state during EN transition.

4. The low slope mode is entered when pin EN goes HIGH while TxD is in LOW state during EN transition. LIN transmitter gets on only after

TxD returns to high after the state transition.

5. The stand−by mode is entered automatically after power−up.

Standby mode

−

−LIN TRX: off

−INH: floating

−LIN term.: current source

−RxD pin: High/Low

−RSTN pin:

Normal mode

(normal slope )

−

−LIN TRX: on

−INH: High/floating

−LIN term.: 30kW

−RxD pin: LIN data

−RSTN pin: High

Normal mode

(low slope )

−

−LIN TRX: on

−INH: High/floating

−LIN term.: 30kW

−RxD pin: LIN data

−RSTN pin: High

Sleep mode

−

−LIN TRX: off

−INH: floating

−LIN term.: current source

−RxD pin:

−RSTN pin: Low

EN changes 0−>1 while TxD=1

EN changes 1−>0 while STB=1

EN changes 1−>0 while STB=0

PD20090610 .01

Figure 4. State Diagram

Normal Slope Mode

In normal slope mode the transceiver can transmit and

receive data via LIN bus with speed up to 20 kBaud. The

transmit data stream of the LIN protocol is present on the

TxD pin and converted by the transmitter into a LIN bus

signal with controlled slew rate to minimize EMC emission.

The receiver consists of the comparator that has a threshold

with hysteresis in respect to the supply voltage and an input

filter to remove bus noise. The LIN output is pulled HIGH

via an internal 30 k

W pull−up resistor. For master

applications it is needed to put an external 1 k

W resistor with

The mode selection is done by EN=HIGH when TxD pin is

HIGH. If STB pin is high during the standby−to−normal

slope mode transition, INH pin is pulled high. Otherwise, it

stays floating.

Low Slope Mode

In low slope mode the slew rate of the signal on the LIN

bus is reduced (rising and falling edges of the LIN bus signal

are longer). This further reduces the EMC emission. As a

consequence the maximum speed on the LIN bus is reduced

up to 10 kBaud. This mode is suited for applications where

the communication speed is not critical. The mode selection