Philips TJA1020 User Guide

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TJA1020

LIN transceiver

Product speciﬁcation Supersedes data of 2001 Dec 17

2002 Jul 17

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

FEATURES General

• Baud rate up to 20 Kbaud

• Very low ElectroMagnetic Emission (EME)

• High ElectroMagnetic Immunity (EMI)

• Low slope mode for an even further reduction of EME

• Passive behaviour in unpowered state

• Input levels compatible with 3.3 and 5 V devices

• Integrated termination resistor for Local Interconnect

Network (LIN) slave applications

• Wake-up source recognition (local or remote).

Low power management

• Very low current consumption in sleep mode with local and remote wake-up.

Protections

• Transmit data (TXD) dominant time-out function

• Bus terminal and battery pin protected against

transients in the automotive environment (ISO7637)

• Bus terminal short-circuit proof to battery and ground

• Thermally protected.

GENERAL DESCRIPTION

The TJA1020 is the interface between the LIN master/slave protocol controller and the physical bus in a Local Interconnect Network (LIN). It is primarily intended forin-vehiclesub-networksusingbaudratesfrom2.4 upto 20 Kbaud.

The transmit data stream of the protocol controller at the TXD input is converted by the LIN transceiver into a bus signal with controlled slew rate and wave shaping to minimize EME. The LIN bus output pin is pulled HIGH via an internal termination resistor. For a master application an external resistor in series with a diode should be connected between pin INH or pin BAT and pin LIN. The receiver detects the data stream at the LIN bus input pin and transfers it via pin RXD to the microcontroller.

In normal transceiver operation the TJA1020 can be switched in the normal slope mode or the low slope mode. In the low slope mode the TJA1020 lengthens the rise and fall slopes of the LIN bus signal, thus further reducing the already very low emission in normal slope mode.

In sleep mode the power consumption of the TJA1020 is verylow,whereasin failure modes the power consumption is reduced to a minimum.

QUICK REFERENCE DATA

SYMBOL PARAMETER MIN. TYP. MAX. UNIT

V I

BAT

supply voltage on pin BAT 5 12 27 V supply current on pin BAT in sleep mode 1 3 8 µA supply current on pin BAT in standby mode; bus recessive 100 400 1000 µA supply current on pin BAT in normal slope mode; bus recessive 100 400 1000 µA supply current on pin BAT in normal slope mode; bus dominant 1 3.5 8.0 mA

LIN

esd(HBM)

DC voltage on pin LIN −27 − +40 V virtual junction temperature −40 − +150 °C electrostatic discharge voltage; human body model;

−4 − +4 kV

pins NWAKE, LIN and BAT

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGES

TJA1020T SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1 TJA1020U − bare die; die dimensions 1480 × 1760 × 375 µm −

2002 Jul 17 2

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

BLOCK DIAGRAM

handbook, full pagewidth

BAT

NWAKE

NSLP

TXD

RXD

WAKE-UP

TIMER

SLEEP/

NORMAL

TIMER

TXD

TIME-OUT

TIMER

CONTROL

TEMPERATURE

PROTECTION

INH

LIN

TJA1020T

RXD/

INT

BUS

TIMER

FILTER

MGU241

GND

Fig.1 Block diagram.

PINNING

SYMBOL PIN DESCRIPTION

RXD 1 receive data output (open-drain);

active LOW after a wake-up event

NSLP 2 sleep control input (active LOW);

controls inhibit output; resets wake-up source ﬂag on TXD and wake-up request on RXD

NWAKE 3 local wake-up input (active LOW);

negative edge triggered

TXD 4 transmit data input; active LOW

output after a local wake-up event GND 5 ground LIN 6 LIN bus line input/output BAT 7 battery supply INH 8 battery related inhibit output for con-

trolling an external voltage regulator;

active HIGH after a wake-up event

handbook, halfpage

RXD

NSLP

NWAKE

TXD

3 4

TJA1020T

MGU242

Fig.2 Pinning diagram.

INH

BAT

LIN

6 5

GND

2002 Jul 17 3

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

FUNCTIONAL DESCRIPTION

The TJA1020 is the interface between the LIN master/slave protocol controller and the physical bus in a Local Interconnect Network (LIN). The LIN transceiver is optimized for the maximum specified LIN transmission speed of 20 Kbaud providing optimum EMC performance due to wave shaping of the LIN output.

Operating modes

The TJA1020 provides two modes of normal operation, one intermediate mode and one very low power mode. Figure 3 shows the state diagram.

handbook, full pagewidth

(NSLP = 1; after 0−>1)

and TXD = 0

STANDBY

INH = HIGH

TERM. = 30 kΩ

RXD = LOW

> t

gotonorm

SLOPE MODE

INH = HIGH

TERM. = 30 kΩ

RXD = LINDATA

trx OFF

LOW

trx ON

(NSLP = 1; after 0−>1)

(NWAKE = 0; after 1−>0)

(NSLP = 0; after 1−>0)

(NSLP = 1; after 0−>1)

and TXD = 1

(LIN = 0; after 1−>0)

and no wake-up event

and NSLP = 0

and TXD = 0

> t

gotonorm

> t

NWAKE

> t

)

BUS

(NSLP = 0; after 1−>0)

> t

gotosleep and no

wake-up event

> t

gotosleep

> t

gotonorm

NORMAL

SLOPE MODE

INH = HIGH

TERM. = 30 kΩ

RXD = LINDATA

trx ON

(NSLP = 1; after 0−>1)

SLEEP

INH = FLOATING

TERM. =

HIGH-OHMIC

RXD = FLOATING

trx OFF

and TXD = 1

switching on BAT

MGU243

> t

gotonorm

trx: transmitter. TERM.: slave termination resistor, connected between pins LIN and BAT.

Fig.3 State diagram.

2002 Jul 17 4

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

Table 1 Operating modes

MODE NSLP TXD (OUTPUT) RXD INH TRANSMITTER REMARKS

Sleep 0 weak pull-down ﬂoating ﬂoating off no wake-up request detected Standby

Normal slope mode

Low slope mode

(1)

0 weak pull-down if

LOW; note 3 HIGH off wake-up request detected; in remote wake-up; strong pull-down if local wake-up; note 2

1 weak pull-down HIGH:

recessivestate

LOW:

dominant state

1 weak pull-down HIGH:

recessivestate

LOW:

dominant state

this mode the microcontroller can read the wake-up source: remote or local wake-up

HIGH normal slope

notes 2, 3 and 4

mode

HIGH low slope mode notes 2, 3 and 5

Notes

1. The standby mode isentered automatically upon any local or remote wake-up event duringsleep mode. Pin INH and the 30 kΩ termination resistor at pin LIN are switched on.

2. The internal wake-up source flag (set if a local wake-up did occur and fed to pin TXD) will be reset when entering normal slope or low slope mode (NSLP goes HIGH).

3. The wake-up interrupt (on pin RXD) is released when entering normal slope or low slope mode (NSLP goes HIGH).

4. The normal slope mode is entered if TXD is set HIGH (set by the microcontroller to recessive) during a positive edge on NSLP. In the event of a short-circuit to ground on pin TXD, the transmitter will be disabled.

5. The low slope mode is entered if pin TXD is pulled LOW (actively set dominant by the microcontroller or due to a failure on TXD) during the positive edge on NSLP.

Sleep mode

This mode is the most power saving mode of the TJA1020 and the default state after power-up (first battery supply). Despiteitsextremelowcurrentconsumption,theTJA1020 can still be waken up remotely via pin LIN, or waken up locally via pin NWAKE, or activated directly via pin NSLP. Filters at the inputs of the receiver (LIN), of pin NWAKE andofpin NSLP are preventing unwanted wake-up events due to automotive transients or EMI. All wake-up events have to be maintained for a certain time period (t t

NWAKE

and t

gotonorm

BUS

The sleep mode is initiated by a falling edge on the pin NSLP driven by the microcontroller. After a filter time continuously driven sleep command (pin NSLP = LOW), pin INH becomes floating.

The sleep mode can be activated independently from the actual level on pin LIN or NWAKE. So it is guaranteed that the lowest power consumption is achievable even in case of a continuous dominant level on pin LIN or a continuous LOW on pin NWAKE.

Standby mode

The standby mode is entered automatically whenever a local or remote wake-up occurs while the TJA1020 is in its sleep mode. These wake-up events activate pin INH and enable the slave termination resistor at the pin LIN. As a result of the HIGH condition on pin INH the voltage regulator and the microcontroller can be activated.

Thestandby mode is signalledby a LOW levelon pin RXD which can be used as an interrupt for the microcontroller.

In sleep mode the internal slave termination between pins LIN and BAT is disabled to minimize the power dissipation in case pin LIN is short-circuited to ground. Only a weak pull-up between pins LIN and BAT is present.

2002 Jul 17 5

In the standby mode (pin NSLP is still LOW), the condition of pin TXD (weak pull-down or strong pull-down) indicates thewake-up source: weak pull-down for aremotewake-up request and strong pull-down for a local wake-up request.

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

Settingpin NSLPHIGHduring standby mode results in the following events:

• An immediate reset of the wake-up source flag; thus

releasing the possible strong pull-down at pin TXD before the actual mode change (after t

gotonorm

) is

performed

• A change into normal slope mode if the HIGH level on

pin NSLP has been maintained for a certain time period (t

gotonorm

) and pin TXD is HIGH

• A change into low slope mode if the HIGH level on pin

NSLP has been maintained for a certain time period (t

gotonorm

) and pin TXD ispulled LOW by the application. In the event of a short-circuit to ground or an open-wire on pin TXD, the LIN output remains recessive (fail safe).

• A reset of the wake-up request signal on pin RXD if the HIGH level on pin NSLP has been maintained for a certain time period (t

gotonorm

Normal slope mode

In the normal slope mode the transceiver is able to transmitandreceivedata via the LIN bus line. The receiver detects the data stream at the LIN bus input pin and transfers it via pin RXD to the microcontroller (see Fig.1): HIGH at a recessive level and LOW at a dominant level on the bus. The receiver has a supply voltage related threshold with hysteresis and an integrated filter to suppress bus line noise. The transmit data stream of the protocol controller at the TXD input is converted by the transmitter into a bus signal with controlled slew rate and wave shaping to minimize EME. The LIN bus output pin is pulled HIGH via an internal slave termination resistor. For a master application an external resistor in series with a diode should be connected between pin INH or BAT on one side and pin LIN on the other side.

The normal slope mode is entered by a HIGH level on pin TXD and a HIGH level on pin NSLP maintained for a certain time period (t

), coming from the sleep or

gotonorm

standby mode. The TJA1020 switches to sleep mode in case of a LOW

level on pin NSLP, maintainedduring a certain time period (t

gotosleep

Low slope mode

In the low slope mode the transmitter output stage drives the LIN bus line with lengthened rise and fall slopes. This will further reduce the already outstanding EME in the normalslopemode. The low slope mode is perfectly suited for applications where transmission speed is not critical. The mode selection is done by the LIN transceiver after a positive edge on pin NSLP, maintained for a certain time period (t

gotonorm

). If pin TXD is LOW at that time, the low slope mode is entered, otherwise the normal mode is entered. The transition to the low slope mode will be executedduring an open pin TXD (fail-safe),ashort-circuit from pin TXD to ground (fail-safe) or an intended LOW level of pin TXD programmed by the microcontroller. The transmitter is enabled after a LOW-to-HIGH transition on pin TXD. In the event of a short-circuit to ground on pin TXD, the transmitter will be disabled.

Wake-up

There are three ways to wake-up a TJA1020 which is in sleep mode:

1. Remote wake-up via a dominant bus state

2. Local wake-up via a negative edge at pin NWAKE

3. Mode change (pin NSLP is HIGH) from sleep mode to

normal slope/low slope mode.

Remote and local wake-up

A falling edge at pin NWAKE followed by a LOW level maintained for a certain time period (t

NWAKE

) results in a local wake-up. The pin NWAKE provides an internal pull-up towards pin BAT.

If, during power-up, pin NWAKE is LOW for a certain period of time (t

) this will also result in a local

NWAKE

wake-up. A falling edge at pin LIN followed by a LOW level

maintained for a certain time period (t

) and a rising

BUS

edge at pin LINrespectively (see Fig.4) results in a remote wake-up.

After a local or remote wake-up pin INH is activated (it goes HIGH) and the internal slave termination resistor is switched on. The wake-up request is indicated by a LOW active wake-up request signal on pin RXD to interrupt the microcontroller.

The only difference between the normal slope mode and the low slope mode is the transmitter behaviour.

2002 Jul 17 6

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

Wake-up via mode transition

It is also possible to set pin INH HIGH with a mode transition towards normal slope/low slope mode via pin NSLP. This is useful for applications with a continuously powered microcontroller.

Wake-up source recognition

The TJA1020 can distinguish between a local wake-up request on pin NWAKE and a remote wake-up request via a dominant bus state. The wake-up source flag is set in case the wake-up request was a local one. The wake-up source can be read on pin TXD in the standby mode. If an external pull-up resistor on pin TXD to the power supply voltage of the microcontroller has been added a HIGH level indicates a remote wake-up request (weak pull-down at pin TXD) and a LOW level indicates a local wake-up request (strong pull-down at pin TXD; much stronger than the external pull-up resistor).

The wake-up request flag (signalled on pin RXD) as well as the wake-up source flag (signalled on pin TXD) are reset immediately, if the microcontroller sets pin NSLP HIGH.

TXD dominant time-out function

A ‘TXD Dominant Time-out’ timer circuit prevents the bus line from being driven to a permanent dominant state (blocking all network communication) if pin TXD is forced permanently LOW by a hardware and/or software application failure. The timer is triggered by a negative edge on pin TXD. If the duration of the LOW level on pin TXDexceedstheinternaltimervalue(t

),thetransmitter

dom

is disabled, driving the bus line into a recessive state. The timer is reset by a positive edge on pin TXD.

Fail-safe features

Pin TXD provides a pull-down to GND in order to force a predefined level on input pin TXD in case the pin TXD is unsupplied.

Pin NSLP provides a pull-down to GND in order to force the transceiver into sleep mode in case the pin NSLP is unsupplied.

Pin RXD is set floating in case of lost power supply on pin BAT.

The current of the transmitter output stage is limited in order to protect the transmitter against short-circuit to pins BAT or GND.

A loss of power (pins BAT and GND) has no impact to the bus line and the microcontroller. There are no reverse currents from the bus. The LIN transceiver can be disconnected from the power supply without influencing the LIN bus.

The output driver at pin LIN is protected against overtemperature conditions. If the junction temperature exceeds the shutdown junction temperature T

j(sd)

, the thermal protection circuit disables the output driver. The driver is enabled again if the junction temperature has been decreased below T

and a recessive level is

j(sd)

present at pin TXD.

2002 Jul 17 7

Philips Semiconductors Product speciﬁcation

LIN transceiver TJA1020

handbook, full pagewidth

LIN

LIN recessive

0.4V

BAT

LIN dominant

sleep mode standby mode

BUS

Fig.4 Wake-up behaviour.

BAT

0.6V

ground

MBL371

BAT

2002 Jul 17 8

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