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INTEGRATED CIRCUITS
DATA SHEET
PCA82C251 CAN transceiver for 24 V systems
Product specification Supersedes data of 1997 Mar 14 File under Integrated Circuits, IC18 2000 Jan 13
Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
FEATURES • Fully compatible with the “ISO 11898-24 V” standard • Slope control to reduce RFI • Thermally protected • Short-circuit proof to battery and ground in 24 V powered systems • Low-current standby mode • An unpowered node does not disturb the bus lines • At least 110 nodes can be connected • High speed (up to 1 Mbaud) • High immunity against electromagnetic interference. QUICK REFERENCE DATA SYMBOL VCC ICC 1/tbit VCAN Vdiff Tamb PARAMETER supply voltage supply current maximum transmission speed CANH, CANL input/output voltage differential bus voltage ambient temperature standby mode non-return-to-zero CONDITIONS − 1 −36 1.5 −40 MIN. 4.5 GENERAL DESCRIPTION
PCA82C251
The PCA82C251 is the interface between the CAN protocol controller and the physical bus. It is primarily intended for applications (up to 1 Mbaud) in trucks and buses. The device provides differential transmit capability to the bus and differential receive capability to the CAN controller.
MAX. 5.5 275 − +36 3.0 +125 V
UNIT µA Mbaud V V °C
ORDERING INFORMATION TYPE NUMBER PCA82C251 PCA82C251T PCA82C251U PACKAGE NAME DIP8 SO8 − DESCRIPTION plastic dual in-line package; 8 leads (300 mil) plastic small outline package; 8 leads body width 3.9 mm bare die; 2840 × 1780 × 380 µm CODE SOT97-1 SOT96-1 −
2000 Jan 13
2
Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
BLOCK DIAGRAM
PCA82C251
handbook, full pagewidth
VCC 3 1 TXD PROTECTION
DRIVER 8 Rs 4 RXD CANL RECEIVER Vref 5 REFERENCE VOLTAGE 6 SLOPE/ STANDBY 7 CANH
PCA82C251
2 GND
MBG613
Fig.1 Block diagram.
PINNING SYMBOL TXD GND VCC RXD Vref CANL CANH Rs PIN 1 2 3 4 5 6 7 8 ground supply voltage receive data output reference voltage output LOW-level CAN voltage input/output HIGH-level CAN voltage input/output slope resistor input DESCRIPTION transmit data input
handbook, halfpage
TXD GND VCC RXD
1 2
8 7
Rs CANH CANL Vref
PCA82C251
3 4
MBG612
6 5
Fig.2 Pin configuration.
2000 Jan 13
3
Philips Semiconductors
Product specification
CAN transceiver for 24 V systems
FUNCTIONAL DESCRIPTION The PCA82C251 is the interface between the CAN protocol controller and the physical bus. It is primarily intended for applications up to 1 Mbaud in trucks and buses. The device provides differential transmit capability to the bus and differential receive capability to the CAN controller. It is fully compatible with the “ISO 11898-24 V” standard. A current limiting circuit protects the transmitter output stage against short-circuit to positive and negative battery voltage. Although the power dissipation is increased during this fault condition, this feature will prevent destruction of the transmitter output stage. If the junction temperature exceeds a value of approximately 160 °C, the limiting current of both transmitter outputs is decreased. Because the transmitter is responsible for the major part of the power dissipation, this will result in a reduced power dissipation and hence a lower chip temperature. All other parts of the IC will remain operating. The thermal protection is particularly needed when a bus line is short-circuited. The CANH and CANL lines are also protected against electrical transients which may occur in an automotive environment. Table 1 Truth table of the CAN transceiver VCC 4.5 to 5.5 V 4.5 to 5.5 V 4.5 < VCC < 5.5 V 0 < VCC < 4.5 V Notes 1. X = don’t care. 2. If another bus node is transmitting a dominant bit, then RXD is logic 0. Table 2 Pin Rs summary MODE standby slope control high-speed TXD 0 1 (or floating) X(1) floating CANH HIGH floating floating if VRs > 0.75VCC floating CANL LOW floating floating if VRs > 0.75VCC floating BUS STATE dominant recessive floating floating
PCA82C251
Pin 8 (Rs) allows three different modes of operation to be selected: high-speed, slope control or standby. For high-speed operation, the transmitter output transistors are simply switched on and off as fast as possible. In this mode, no measures are taken to limit the rise and fall slope. Use of a shielded cable is recommended to avoid RFI problems. The high-speed mode is selected by connecting pin 8 to ground. The slope control mode allows the use of an unshielded twisted pair or a parallel pair of wires as bus lines. To reduce RFI, the rise and fall slope should be limited. The rise and fall slope can be programmed with a resistor connected from pin 8 to ground. The slope is proportional to the current output at pin 8. If a HIGH level is applied to pin 8, the circuit enters a low current standby mode. In this mode, the transmitter is switched off and the receiver is switched to a low current. If dominant bits are detected (differential bus voltage >0.9 V), RXD will be switched to a LOW level. The microcontro.