SN65HVDA195-Q1

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SLLS961A – JULY 2009 – REVISED OCTOBER 2009

Table 1. Operating Modes

LIN BUS

MODE

EN

RXD

INH

TRANSMITTER

COMMENTS

TERMINATION

Sleep

Low

Floating

Weak current pullup

High impedance

Off

Wake-up event detected, waiting

Standby

Low

Low

30 k

Ω (typ)

High

Off

on MCU to set EN

Normal

High

LIN bus data

30 k

Ω (typ)

High

On

LIN transmission up to 20 kbps

Normal Mode

This is the normal operational mode, in which the receiver and driver are active, and LIN transmission up to the

LIN specified maximum of 20 kbps is supported. The receiver detects the data stream on the LIN bus and

outputs it on RXD for the LIN controller, where recessive on the LIN bus is a digital high, and dominate on the

LIN bus is digital low. The driver transmits input data on TXD to the LIN bus. Normal mode is entered as EN

transitions high while the SN65HVDA195 is in sleep or standby mode.

Sleep Mode

Sleep mode is the power saving mode for the SN65HVDA195 and the default state after power up (assuming EN

is low during power up). Even with the extremely low current consumption in this mode, the SN65HVDA195 can

still wake up from LIN bus via a wake-up signal, a low on NWake, or if EN is set high. The LIN bus and NWake

are filtered to prevent false wake-up events. The wake-up events must be active for their respective time periods

The sleep mode is entered by setting EN low.

While the device is in sleep mode, the following conditions exist:

•

The LIN bus driver is disabled and the internal LIN bus termination is switched off (to minimize power loss if

LIN is short circuited to ground). However, the weak current pullup is active to prevent false wake-up events

in case an external connection to the LIN bus is lost.

•

The normal receiver is disabled.

•

INH is high impedance.

•

EN input, NWake input, and the LIN wake-up receiver are active.

Wake-Up Events

There are three ways to wake up the SN65HVDA195 from sleep mode:

•

Remote wake-up via recessive (high) to dominant (low) state transition on LIN bus. The dominant state must

from disturbances on the LIN bus or if the bus is shorted to ground).

•

wake-ups from disturbances on NWake)

•

Local wake-up via EN being set high

Standby Mode

This mode is entered whenever a wake-up event occurs via LIN bus or NWake while the SN65HVDA195 is in

sleep mode. The LIN bus slave termination circuit and INH are turned on when standby mode is entered. The

application system powers up once INH is turned on, assuming the system is using a voltage regulator

connected via INH. Standby mode is signaled via a low level on RXD.

When EN is set high while the SN65HVDA195 is in standby mode the device returns to normal mode and the

normal transmission paths from TXD to LIN bus and LIN bus to RXD are enabled.

Copyright © 2009, Texas Instruments Incorporated

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