Philips PCA82C252, TJA1053, TJA1054, TJA1054A Technical data

Philips Semiconductors Systems Laboratory Hamburg, Germany

APPLICATION HINTS Fault-tolerant CAN Transceiver

Application Hints

Fault-tolerant CAN Transceiver

PCA82C252 / TJA1053 / TJA1054 / TJA1054A

Application Hints FTCAN 3_1.PDF

Version 3.1

Date : 23

of November 2001

Philips Semiconductors

Philips Semiconductors Systems Laboratory Hamburg, Germany

APPLICATION HINTS Fault-tolerant CAN Transceiver

Revision History

Changes Version 1.0 -> 2.0 :

1. Chapter 3, calculation examples for PCA82C252 and TJA1053 added, new aspects

2. Chapter 4, calculation hints for termination resistors added, new aspects

Changes Version 2.0 -> 2.1 :

1. Chapter 6 added

2. Chapter 7 added

3. Chapter 8 added

Changes Version 2.1 -> 2.2 :

1. Chapter 5, clarification that external ESD diodes are optional for further improvements

2. Chapter 8 added, Software design hints ( previous chapter 8 re-numbered to chapter 9 )

3. Chapter 9, FAQ 9.6, No communication at CANH to VCC short circuit

Changes Version 2.2 -> 3.0 :

1. Foreword added

2. Chapter 2 added, Upgrading Note TJA1053 -> TJA1054

3. Chapter 3 added, Mode Control of the TJA1054

4. Chapter 5, formula 11 corrected, calculation example updated

5. Chapter 10, Software design hints dealing with the pin ERR added

Changes Version 3.0 -> 3.1 :

1. Editorial changes

2. Chapter 8, series resistor at pin WAKE, more details

3. Chapter 9 added, series resistor at pins TXD

Foreword

In this document, application related information for the various fault-tolerant transceiver implementations from Philips Semiconductors is collected. The different transceivers are a result of a continuous improvement of the fault-tolerant and system performance. The first available product in the mar ket was the PCA82C252, followed by the TJA1053 and lat er on by the TJA1054. In the mean time even the TJA1054 has become improved with respect to ESD capabilities. The so-called TJA1054A behaves identical to the TJA1054 but offers a higher ESD robustness on the bus- related pins. T hus wherever the T JA1054 is m entioned within th is document it could also be read as TJA1054A, except in case a certain transceiver type is mentioned explicitly.

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APPLICATION HINTS Fault-tolerant CAN Transceiver

Table of Contents :

1. Comparison PCA82C252 / TJA1053 / TJA1054 / TJA1054A.........................................................6

1.1. System parameters........................................................................................................................6

1.2. Device parameters.........................................................................................................................6

2. Upgrading a TJA1053 Design with the TJA1054...........................................................................7

2.1. Overview........................................................................................................................................7

2.2. Hardware Issues............................................................................................................................7

2.2.1. External Components..............................................................................................................7

2.2.2. Wake-up sensitivity at pin WAKE............................................................................................8

2.2.3. Current consumption...............................................................................................................8

2.2.4. Operating Voltage Range........................................................................................................8

2.3. Software Issues .............................................................................................................................9

2.3.1. Error signalling via pin ERR ....................................................................................................9

2.3.1.1. Software polls pin ERR.....................................................................................................9

2.3.1.2. Software reads pin ERR during CAN interrupt service only.............................................9

2.3.2. VCC Standby / PWON Standby..............................................................................................9

2.3.3. First Battery Connection, behaviour of pin INH.......................................................................9

2.3.4. Goto-Sleep / Wake-up Priority ................................................................................................9

2.3.5. Other issues ..........................................................................................................................10

2.4. Interoperability : Mixed Systems with TJA1053 and TJA1054 ....................................................10

2.4.1. Overview ...............................................................................................................................10

2.4.2. Hardware Interoperability Investigations...............................................................................10

2.4.3. Results of Hardware Interoperability Investigation................................................................11

1.5. Conclusion ...................................................................................................................................11

1.6. Migration Checklist.......................................................................................................................12

3. Mode Control with the TJA1054....................................................................................................13

3.1. Overview......................................................................................................................................13

3.2. Operating Modes .........................................................................................................................14

3.2.1. Normal Mode.........................................................................................................................14

3.2.2. Goto Sleep ............................................................................................................................15

3.2.3. Stby Sleep.............................................................................................................................15

3.2.4. PWON Stby...........................................................................................................................15

3.3. System Wake-up..........................................................................................................................15

3.3.1. Local wake-up .......................................................................................................................15

3.3.2. Remote wake-up ...................................................................................................................15

3.3.3. Mode change.........................................................................................................................15

3.4. State diagrams.............................................................................................................................16

3.4.1. PWON Flag ...........................................................................................................................16

3.4.2. Pin INH..................................................................................................................................16

3.4.3. Wake-up Flag........................................................................................................................16

3.4.4. Pin RXD.................................................................................................................................16

3.4.5. Pin ERR.................................................................................................................................17

4. Vcc Supply and Recommended Bypass Capacitance ...............................................................18

4.1. List of used Abbreviations............................................................................................................18

1.2. Summary......................................................................................................................................19

1.3. Average Supply Current at Absence of Bus Short-Circuit Conditions.........................................20

1.3.1. Maximum dominant supply current (without bus wiring faults) .............................................20

1.3.1.1. Example calculation................................................................................................... .....20

1.3.2. Thermal considerations (without bus wiring faults)...............................................................20

1.3.2.1. Example calculation................................................................................................... .....20

1.4. Average Supply Current at Presence of a Short-Circuit of one Bus Wire ..................................21

1.4.1. Maximum dominant supply current (with CANH shorted to GND)........................................21

1.4.1.1. Example calculation........................................................................................................21

Application Hints V3.1 Page 3 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

1.4.2. Thermal considerations (with CANH shorted to GND)..........................................................21

1.4.2.1. Example calculation................................................................................................... .....21

1.4.3. Vcc extra supply current in single fault condition..................................................................22

1.1.1.1. Example calculation................................................................................................... .....22

1.5. Worst Case Max Vcc Supply at Presence of a Dual Short Circuit...............................................23

1.5.1. Max Vcc supply current in worst case dual fault condition....................................................23

1.5.1.1. Example calculation................................................................................................... .....23

1.5.2. Vcc extra supply current in dual fault condition.....................................................................24

1.1.1.1. Example calculation................................................................................................... .....24

1.6. Calculation of worst-case bypass capacitor.................................................................................24

1.1.1. Example calculation, separate supplied transceiver @ 83,33kBit/s .....................................25

1.1.2. Example calculation, shared supply......................................................................................25

5. Bus Termination and EMC issues ................................................................................................26

5.1. How to dimension the Bus Termination Resistor values, some basic rules................................26

5.1.1. Variable System Size, Optional Nodes .................................................................................26

5.1.1.1. Example calculation, Variable System Size ...................................................................27

5.2. Tolerances of Bus Termination Resistors, EMC Considerations.................................................27

5.3. Output Current and Power Dissipation of Bus Termination Resistors R

5.3.1. Summary...............................................................................................................................28

5.3.2. Average power dissipation, no bus fail ures ..........................................................................28

5.3.2.1. Example calculation, average power dissipation............................................................28

5.3.3. Maximum continuous power dissipation (single bus failure).................................................28

5.3.3.1. Example calculation, maximum continuous power dissipation ......................................28

5.3.4. Maximum peak power dissipation (single bus failure) ..........................................................29

5.3.4.1. Example calculation, maximum peak power dissipation................................................29

....................................28

6. ESD Protection...............................................................................................................................30

6.1. Improved ESD capability of TJA1054A........................................................................................30

6.2. Optional external ESD Improvement ...........................................................................................30

7. Series Resistor at Pin BAT............................................................................................................31

8. Series Resistor at Pin WAKE........................................................................................................32

1.1. Parameters defining the range of R

1.2. Calculating the limits of R

...........................................................................................................33

...........................................................................................32

1.3. Example calculation.....................................................................................................................33

9. Series Resistor at Pin TXD............................................................................................................34

9.1. Parameters defining the range of R

9.2. Calculating the Limits of R

......................................................................................................34

TXD

........................................................................................34

TXD

9.3. Example calculation.....................................................................................................................34

10. Hardware Design Checklist...........................................................................................................35

11. Software Design Hints...................................................................................................................36

11.1. System Sleep Procedure...........................................................................................................36

11.2. Using the ERR output for failure diagnosis................................................................................37

11.2.1. ERR signal at open bus wires.............................................................................................37

11.2.1.1. Behaviour using PCA82C252 / TJA1053 .....................................................................37

11.2.1.2. Behaviour using TJA1054 ............................................................................................38

11.2.2. ERR signal while CANH shorted to GND or CANL shorted to VCC...................................38

11.2.3. ERR signal while other short circuit conditions...................................................................38

11.3. Using ERR for Reading out the PWON Flag.............................................................................39

Application Hints V3.1 Page 4 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

12. Frequently Asked Questions ........................................................................................................40

12.1. The transceiver does not enter the Sleep Mode........................................................................40

12.2. System operates in Single Wire Mode all time..........................................................................40

12.3. System does not wake-up, even if there is bus activity.............................................................40

12.4. Transceiver is damaged when ex terna l tools are con nected ....................................................41

12.5. CAN tool cannot communicate with certain application.............................................................41

12.6. No communication at CANH to VCC short circuit......................................................................41

Application Hints V3.1 Page 5 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

Comparison PCA82C252 / TJA1053 / TJA1054 / TJA1054A

1.1. System parameters

Key PCA82C252 TJA1053 TJA1054

System size 10 – 15 nodes Speed 20 - <125 kbps

1) 2)

10 – 15 nodes

20 – 125 kbps 40 – 125 kbps Emission + + ++ Immunity + + ++ TxD dominant monitoring no yes yes Extended bus failure

no no yes management (CANH to Vcc) Resolved problem of

no yes yes arbitration across open failures

1) The limit is give n by the perform ance during C ANH to ground failures , which v ery much depends on the size and type of cable used.

2) The limit is given by the wake-up capability during CANH to ground failures, which very much depends on the values of the distri buted t erm inations acros s the n etwork . T heref ore, exact f igures of system size cannot be given.

3) W ith CANH to VBAT failures the de lay of the dominant edge is increased. The max imum speed strongly depends on the inductance of the cable used.

> 32 nodes

1.2. Device parameters

Key PCA82C252 TJA1053 TJA1054 TJA1054A

Current consumption in Normal Mode (I

) Current consumption in Standby Modes (I I

)

BAT

Minimum operating voltage Prevention of VBAT reverse current

WAKE sensitivit y negative edge negative edge both edges both edges Vcc Standby mode yes yes no no ERR reporting of open failures ESD Protection pins RTH / RTL / CANH / CANL

1) In case a module looses its battery connection, a reverse power supply of this module via the CAN bus lines is prevent ed. For the PC A82C252 and t he TJA1053 a n external diode at the battery pin of the transceiver is required. This diode is required additionally to the control unit’s polarity protection diode typically implemented at the battery connector of the entire module.

6 mA (rec)

29 mA (dom)

6 mA (rec)

29 mA (dom)

7 mA (rec)

17 mA (dom)

70 uA 70 uA 30 uA 30 uA

6V 6V 5V 5V no no yes yes

during frame only during frame only during frame and

inter frame space 2kV Human Body 200V Machine M.

2kV Human Body 200V Machine M.

2kV Human Body

200V Machine M.

7 mA (rec)

17 mA (dom)

during frame and inter frame space 4kV Human Body 300V Machine M.

Application Hints V3.1 Page 6 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

2. Upgrading a TJA1053 Design with the TJA1054

2.1. Overview

The TJA1054 is a fau lt-toleran t CAN trans ceiver suitable for net works including up to 32 nodes and is the compatible successor of the well-known TJA1053. Compared with the TJA1053, the TJA1054 provides several enhanced features:

•

Extremely reduced electro-magnetic emission (EME)

•

Very good electro-magnetic im munity (EMI)

•

Enhanced bus failure management (short circuits to 5V are tolerated)

•

Improved error signalling

•

Improved behaviour during “Loss of Power” situations

The TJA1054 is designed to be downward com patible to the T JA1053 and can be us ed in m ost of the existing TJA1053 applicati ons without any changes in hardware and softwar e. Nevertheless, due to the enhanced functionalit y there are some points to be cons idered if the TJA105 3 is replaced by the TJA1054. The following chapters disc uss all hardware and software issues i n detail in order to allo w a smooth migration from the TJA1053 to the TJA1054. Special attention is paid to inter operabilit y issues giving the conf idence that both devices can be used simultaneously within one network. Validation showed that a “step-by-step” introduction of the TJA1054 into an existing TJA1053 system can be made without risk.

2.2. Hardware Issues

2.2.1. External Components

When the TJA1053 is replaced by a TJA1054, t wo external hardware c omponents ma y be removed (see also figure 1) :

•

Reverse current protection diode at pin BAT

•

Pulse lengthening capacitor at pin ERR

The extra diode for th e TJA1053 is needed to suppress a rever se power suppl y of the contro l unit if the battery connection of the e ntire unit was lost. For the TJA1053, a c urrent flow f rom the CANL bus line backward to the pin BAT of the transceiver was pos sible if the transceiver was not powered. In some applications, this re verse current was high enough to s upply the m icrocontroller un intentionall y. The TJA1054 is internally protected against such reverse currents making the diode superfluous.

Reading the pin ERR during the normal CAN interrupt service routine was not possible for the TJA1053 in case of “ open f ailures ” on t he bus l ines . Here, the so- called “ ack nowledge bi t” of an y valid CAN message cleared an already detected “open failure” at the pin ERR. Therefore, an external lengthening capacit or was required for the TJ A1053 in order to keep t he detected failure signa l valid until the interrupt service routine was executed by the host uC. The TJA1054 does not require this extr a len gth eni ng c a pacitor since the pin E RR no w i nternally keeps the failure signal active. ( see also 11.2.1. )

Application Hints V3.1 Page 7 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

100n

VCC

TXD TXD

RXD RXD

I/O STB

CAN

GND

RTH***

RTL***

CAN

bus

* For further EMC optimization a series resistor could be applied in case the bus timing parameters allow this additional delay caused by the additional R/C time constant. ** Size of capacitor depends on regulator. *** Size of termination resistors depends on system size. The overall system termination should be about 100 Ohms per CAN line.

optional *

<150pF

ERRI/O

470n

CANH

RTH

RTL

CANL

ENI/O

PCA82C252

TJA1053

TJA1054

GND

INH

BAT

WAKE

1k - 2k

10n

> 1k8

<180k

WAKE-UP

BAT

Figure 1 : Typical application circuitry using the TJA1053 and the TJA1054

2.2.2. Wake-up sensitivity at pin WAKE

The wake-up input of the TJ A1054 is s ensitiv e on bo th edg es, whereas the T JA1053 was s ensit ive on the falling edge only. This has typically no impact on the application since such external wake-up events are usually pulses including both edges. Another improvem ent of the TJ A1054 is that wak e-up events have higher pr iority than the goto-sle ep command. System s using the TJA1053 may lose such a wake-up event. Consequent ly, a TJA1053 node may keep sleeping without starti ng the voltage regu lator although a wake- up request has been driven to the pin W AKE. The TJ A1054 will now reco gnise any wak e-up event independentl y from the current command setting of the host CPU.

2.2.3. Current consumption

The total current cons um ption of the TJ A1054 is reduc ed c om pared to t he T JA1053 , es pec iall y durin g low-power modes. The slightly increased short circuit current of the CANH bus driver within the TJA1054 is compensated by its reduced normal mode supply current during dominant bus states. Thus, there is no im pact to the applications power s upply concept. But introduction of the TJA1054 provides a much lower sleep current per control unit now compared with the TJA1053.

Condition TJA1053 TJA1054

Current consumption in Normal Mode, I

Current consumption in Low-power Modes, I

BAT + ICC

6 mA recessive 29mA dominant

7 mA recessive 17mA dominant

70uA 30uA

2.2.4. Operating Voltage Range

In order to increase the system perf ormance during low battery conditions, the T JA1054 now allows operation down to 5V at the pin BAT, whereas the TJA1053 required at least 6V.

Application Hints V3.1 Page 8 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

2.3. Software Issues

2.3.1. Error signalling via pin ERR

As already mention ed before, the behavi our of the error signa lling at the pin ERR is im proved within the TJA1054. This al lows removing the ext ernal lengthening capacitor needed for the T JA1053 (see also 2.1). This new behaviour of the TJA1054 may have an impact on application software if the TJA1053 was used

2.3.1.1. Software polls pin ERR

Application software polling the pin ERR will see fewer transitions if th e TJA1053 is replaced b y the TJA1054. Especiall y during “open failures” on th e bus lines , the soft ware load cause d by ERR eve nts is reduced if the TJA1054 is used.

2.3.1.2.Software reads pin ERR during CAN interrupt service only

Here, the “open failures” are now detected TJA1053 has signal led no problem. Thus , a s im ple migration to the TJ A105 4 a utomatically im proves a software driven diagnosis function.

2.3.2. VCC Standby / PWON Standby

The VCC Standby Mode k nown f rom the T JA1053 is replaced b y the so-c alled PWO N Standb y Mode in the TJA1054 (STB = 1; EN = 0). There is no change in functionality between both transceivers except for the CANL biasing level. The TJA1053 drives 5V to CANL through pin RTL and the termination resistor, whi le the TJA1054 now drives 12V to CAN L using the same path. This has no impact on the overall system performance if both transceivers are m ixed in one network. Software is not influenced since both transc eivers provide the same status inf ormation to the microcontr oller via ERR and RXD.

without

external lengthening capacitor. Two scenarios are possible:

and

signalled by the TJA1054 as desired, whereas the

2.3.3. First Battery Connection, behaviour of pin INH

The TJA1053 allows to be s et into Sleep Mode ( INH floating) direc tly after first batter y connection by driving the goto-sleep com mand to the control pins ST B and EN (“01”) . The TJ A1054 needs t o be set into Normal Mode bef ore accepting the first go to-sleep command af ter first connectio n of the batter y supply. After setting Normal Mode both devices behave identical concerning this item. An internal power-on reset signal within the TJA1054 makes sure that the transceiver is reset successfully after power- up and the INH output is saf ely set to batter y level. This internal reset si gnal is cleared whenever the Norm al Mode is entered once. There are no special timing requir ements to clear the internal reset sig nal thus sof tware just has to se t the Norm al Mode via STB a nd EN fol lowed by any other control cod e. Within mos t of the existing app lications this is already implem ented inside of the systems cold-start routines.

2.3.4. Goto-Sleep / Wake-up Priority

The pin INH of the TJ A1053 does ignore wak e-up events in case these wake-up events are present while the goto-sleep command is continuously driven to t he tr a ns c ei ver vi a pi ns STB and EN ( ST B = 0 / EN = 1). After the goto-sleep filter tim e ( see dat a shee ts T JA1054/T JA10 54A : “ react ion tim e of goto sleep command” ) the INH flip-flop is continuously cleared thus setting the pin INH to a floating condition. Wak e-up events are forwar ded to INH first with releasing the goto- sleep comm and. Thus a systems voltage regu lator connected to INH will becom e disabled e ven if there is a pend ing wake-up request. Nevertheless RXD and ERR will signal the wake-up event with a LOW output level independently from the pending goto-sleep command. For the TJA1054 this behaviour is improved and no wake-up event is lost with respec t to the pin INH. Within the TJA1054 the wake-up events ha ve a higher priority than the goto-sl eep command. Thus any wake-up event will reset IN H to a HIG H out put le vel i ndepen dentl y from the goto-s leep c omm and. RXD and ERR will reflect the wake-up condition with a LOW output level as known from the TJA1053. From software point of view it is highl y recommended for both transc eivers monitoring the pi ns RXD and/or ERR whenever the goto-sleep command was executed in order to detect a wake-up event

Application Hints V3.1 Page 9 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

while the system s hould f all in to s l eep mode. INH might keep HIG H or become HIG H ag ai n c aus e d by a wake-up event before the supply of the uC was successfully disabled. ( see also 11.1. )

2.3.5. Other issues

Experiences with dif ferent software drivers have sho wn the advantage to implement a kind of CAN communication m onitoring in software, expecting CAN b us events in certain time fr ames. At least a reception of mes sages or succ essful transm issions should appear in or der to get conf idence, th at the CAN bus is still operating properly. This is especially important for recovery from dual bus failure situations towards single bus failure situations. Due to the automatic transmit message repetition mechanism of a CAN protocol engine it might happen that a node r etransm its a message forever in case t here is no ack nowledge rec eived fr om the bus. This continuously transm itting node might lock the bus system and thus prevents other nodes to recover from a dual bus failure situation towards a single bus failure situation. Therefore, whenever there is no response from the CAN bus within a reasonable time, pending transmission requests should be abor ted in software. This will inc rease the system avai lability during certain bus failure conditions, which require single wire operation.

2.4. Interoperability : Mixed Systems with TJA1053 and TJA1054

2.4.1. Overview

During developm ent of the TJA1054 special attention was paid to interop erability issues in order to allow a smooth m igration of existi ng applicatio ns by simple replacement of the T JA1053. Part icularly, the enhancements of the bus f ai lure management (5V s hor t cir cuits) have been included very car ef ul l y into the existing circuitry to avoid system hang-ups, if both transceivers are mixed in one system. The TJA1054 is designed to replace the TJA1053 within running car series production without interoperability risk. Interoperability of both devices has been proved in system simulation as well as in hardware investigation. The key results of these investigations are :

•

A pure TJA1054 network solves the known weaknesses of a TJA1053 system

( wake-up of big networks with failure HxGND, short circuits to 5V .... )

•

A mixed system of TJA1053 and TJA1054 has at least the same performance as the pure

TJA1053 system; in some aspects the growing presence of T J A1054 no des i n th e n et work even improves the overall system performance

•

T aking into consi deration the is sues desc ribed in the previous cha pters, m ixed systems of both

transceiver are possible at any ratio without restrictions

2.4.2. Hardware Interoperability Investigations

In order to investigate in teroperability issues of th e transceiver, a network with 25 nodes was set up and investigated in detail. A typical topology including star points was chosen according to real automotive applicat ions. This topology inc ludes cable stubs with m ore than 5 meters and more than 55 meters overall cable length. Worst case scenarios were analysed including weak bus failure conditions, double failures, ground shifts and power sup ply drops. Esp ecially, oper ating mode c hanges (Norm al Mode / Sta ndby / Sleep) were performed simultaneously with bus failure situations.

Application Hints V3.1 Page 10 of 41

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2.4.3. Results of Hardware Interoperability Investigation

The following table gives an overview about the mixed system investigations using the TJA1053 together with the TJA10 54 in different mixing ratios. An assessment is made compar ed with a pure TJA1053 system with same topology.

Bus Failure

0 none 1 H // 2 L // 3HxBAT

3a HxVCC

4LxGND 5HxGND 6LxBAT

6a LxVCC

7HxL

9 9

- 9

9 9

Communication with

( incl. resistive failures )

Standard Communication

9 9

- 9

9 9

Communication at

9 9

- 9

9 9

Low Battery Voltages

Ground Shift (+/- 1.5V)

combined with Bus

Mode Changes / Wake-up

- 9

9 9

- 9

Failure Conditions

- 9

9 9

- 9

9 9

Loss of Termination

Communication with local

Key :

(

-- ) mixed system behaves

(

99 ) mixed system behaves

) mixed system behaves

(

than a pure TJA1053 system

better

to a pure TJA1053 system

equal

worse

than a pure TJA1053 system

2.5. Conclusion

Both transceivers, T JA1053 and TJA1054, are in teroperable and can be us ed simultaneously within the same network. This allows migrating gradually from TJA1053 to TJA1054 in running car mass production. Due to new features intr oduc ed wit h the T JA1054, exis ting T JA10 53 a pplicat ions nee d to be r eview ed according to the comments within this report before replacing the transceiver.

Application Hints V3.1 Page 11 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

2.6. Migration Checklist

Item TJA1053 TJA1054 Comment

Diode @ pin BAT needed can be removed no reverse power supplying by

TJA1054

Capacitor @ pin ERR depends on

software

Sensitivity of pin WAKE falling edge only both edges check behaviour of system wake-up

Goto-sleep command after first battery connection

Goto-sleep command, priority of wake-up event

always possible possible only after

INH becomes floating the time goto-sleep is driven even if there is a wake-up coming

can be removed function is integrated into the

TJA1054

via pin WAKE

Internal power-on signal has to be Normal Mode was entered once

INH keeps HIGH if there is a wake-up coming during gotosleep is driven

cleared by setting the TJA1054 into

Normal Mode after first battery

connection

It is recommended to monitor pin

RXD and/or pin ERR after goto-

sleep in order to detect a wake-up

event during the transition into

Sleep Mode.

Application Hints V3.1 Page 12 of 41

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APPLICATION HINTS Fault-tolerant CAN Transceiver

3. Mode Control with the TJA1054

3.1. Overview

The fault tolerant CA N trans c eiv er T J A1054 provides an integrated functi ona lity controlling an external voltage regulator in order to design low power CAN bus systems with remote and local wake-up capabilities. A dedicated INH pin allows disabling the entire power supply of a control unit, thus reducing the overall system power consumption to a m inimum. The transceiver is the only supplied component during such a low-power state. Following figure shows an application example using the TJA1054.

VCC

TXD TXD

RXD RXD

I/O STB

CAN

GND

RTH***

RTL***

CAN

bus

optional *

ENI/O

ERRI/O

CANH

<150pF

RTH

RTL

CANL

<150pF

TJA1054

GND

INH

BAT

WAKE

100n

1k - 2k

10n

> 1k8

<180k

WAKE-UP

BAT

Figure 2 : Typical application of the TJA1054

As shown within Figure 2 the transceiver is powered d irectly from the battery s upply via the pin BAT. This allows disabling the VCC supply entirely during tim e phases, the CAN bus is not required b y the system. Therefore two control pins STB and EN coming from the host microcontroller are used to control the actual mode of operation like normal communication or low-power operation. For wake-up purposes a battery-related WAKE pin is provided. In addition to bus fail ure information and the CAN receive d bit stream, the pins ERR and RXD are used to signal wake-up requests towards the application controller.

Application Hints V3.1 Page 13 of 41

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Philips PCA82C252, TJA1053, TJA1054, TJA1054A Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual