TJA1053 Fault-tolerant CAN transceiver

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Philips SemiconductorsProduct specificationFault-tolerant CAN transceiverTJA1053PINNINGSYMBOL PIN DESCRIPTIONINH 1 inhibit output for switching external5 V regulatorTXD 2 transmit data input, when LOW busdata will be dominant, when HIGHbus data will be recessiveRXD 3 receive data output, when LOW busdata will be dominantNERR 4 error output pin, when LOW a buserror existsSTB 5 not standby digital control inputsignal (active LOW)EN 6 enable digital control input signalWAKE 7 not wake input signal, when pulleddown INH becomes active forwake-up (active LOW)RTH 8 termination resistor, CANH line willbe high-impedance with certain buserrorsRTL 9 termination resistor, CANL line will behigh-impedance with certain buserrorsV CC 10 supply voltage (+5 V)CANH 11 high voltage bus line, will be HIGH indominant stateCANL 12 low voltage bus line, will be LOW indominant stateGND 13 groundBAT 14 battery voltagehandbook, halfpageINH 114 BATTXD 213RXD 312NERRSTB45TJA1053T 1110EN 69WAKE 78MGL182GNDCANLCANHV CCRTLRTHFig.2 Pin configuration.2000 Dec 18 4
Philips SemiconductorsProduct specificationFault-tolerant CAN transceiverTJA1053FUNCTIONAL DESCRIPTIONThe TJA1053 is the interface between the CAN protocolcontroller and the physical bus. It is primarily intended forlow speed applications, up to 125 kbaud, in passengercars. The device provides differential transmit capability tothe bus and differential receive capability to the CANcontroller.To reduce RF interference the rise and fall slope arelimited. This allows the use of an unshielded twisted pair ora parallel pair of wires for the bus. Moreover, it supportstransmission capability on either bus wire if one of the buswires is corrupted. The failure detection logic automaticallyselects a suitable transmission mode.In normal operation (no wiring failures) the differentialreceiver is output to RXD. The differential receiver inputsare connected to CANH and CANL through integratedfilters. The filtered input signals are also used for the singlewire receivers. The CANH and CANL receivers havethreshold voltages that ensure a maximum noise margin insingle-wire modes.A timer has been integrated at the TXD input. This timerprevents the TJA1053 driving the bus lines to permanentdominant state.Failure detectorThe failure detector is active in the normal operation modeand detects the following single bus failures and switchesto an appropriate mode:1. CANH wire interrupted2. CANL wire interrupted3. CANH short-circuited to battery4. CANL short-circuited to ground5. CANH short-circuited to ground6. CANL short-circuited to battery7. CANL mutually shorted to CANH.The differential receiver threshold is set at −2.9 V.This ensures correct reception in the normal operatingmodes and, in the event of failures 1, 2 and 5 with a noisemargin as high as possible. These failures, or recoveryfrom them, do not destroy ongoing transmissions.Failures 3 and 6 are detected by comparators connectedto CANH and CANL, respectively. If the comparatorthreshold is exceeded for a certain period of time, thereception is switched to the single-wire mode.This time is needed to avoid false triggering by external RFfields. Recovery from these failures is detectedautomatically after a certain time-out (filtering) and notransmission is lost. The CANH driver and the RTH pin areswitched off in the event of failure 3.Failures 4 and 7 initially result in a permanent dominantlevel at RXD. After a time-out, the CANL driver and theRTL pin are switched off. Only a weak pull-up at RTLremains. Reception continues by switching to thesingle-wire mode via CANH. When failures 4 or 7 areremoved, the recessive bus levels are restored. If thedifferential voltage remains below the recessive thresholdlevel for a certain period of time, reception andtransmission switch back to the differential mode.If any of the seven wiring failures occur, the output NERRwill be made LOW. On error recovery, NERR will be madeHIGH again.During all single-wire transmissions, the EMCperformance (both immunity and emission) is worse thanin the differential mode. Integrated receiver filterssuppress any HF noise induced into the bus wires.The cut-off frequency of these filters is a compromisebetween propagation delay and HF suppression. In thesingle-wire mode, low frequency noise cannot bedistinguished from the required signal.Low power modesThe transceiver provides 3 low power modes which can beentered and exited via pins STB and EN (see Table 1).The sleep mode is the mode with the lowest powerconsumption. The INH pin is switched to high-impedancefor deactivation of external voltage regulators. CANL isbiased to the battery voltage via the RTL output. If thesupply voltage is provided the RXD and NERR will signalthe wake-up interruptThe V BAT standby mode will react the same as the sleepmode with an active INH output.The V CC standby mode is the V BAT standby with RTLswitched to the V CC voltage. In this mode the NERR outputsignals the V BAT power-on flag and the RXD output willshow the wake-up interrupt.2000 Dec 18 5
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TJA1053 Fault-tolerant CAN transceiver

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