Document
PCA82C251
CAN transceiver for 24 V systems
Rev. 04 — 25 August 2011 Product data sheet
1. General description
The PCA82C251 is the interface between a CAN protocol controller and the physical bus. The device provides differential transmit capability to the bus and differential receive capability to the CAN controller.
2. Features and benefits
Fully compatible with the “ISO 11898-24 V” standard Slope control to reduce Radio Frequency Interference (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 MBd) High immunity against electromagnetic interference.
3. Applications
High-speed applications (up to 1 MBd) in trucks and busses.
4. Quick reference data
Table 1. Symbol VCC ICC 1/tbit VCAN Vdiff tPD Tamb Quick reference data Parameter supply voltage supply current maximum transmission speed CANH, CANL input/output voltage differential bus voltage propagation delay ambient temperature High-speed mode Standby mode non-return-to-zero Conditions Min 4.5 1 36 1.5 40 Max 5.5 275 +36 3.0 50 +125 Unit V A MBd V V ns C
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NXP Semiconductors
PCA82C251
CAN transceiver for 24 V systems
5. Ordering information
Table 2. Ordering information Package Name PCA82C251T SO8 Description plastic small outline package; 8 leads; body width 3.9 mm Version SOT96-1 Type number
6. Block diagram
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
7. Pinning information
7.1 Pinning
TXD GND VCC RXD
1 2
8 7
Rs CANH CANL Vref
PCA82C251
3 4
mbg612
6 5
Fig 2.
Pin configuration
PCA82C251
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 04 — 25 August 2011
2 of 17
NXP Semiconductors
PCA82C251
CAN transceiver for 24 V systems
7.2 Pin description
Table 3. Symbol TXD GND VCC RXD Vref CANL CANH Rs Pin description Pin 1 2 3 4 5 6 7 8 Description transmit data input ground supply voltage receive data output reference voltage output LOW-level CAN voltage input/output HIGH-level CAN voltage input/output slope resistor input
8. Functional description
The PCA82C251 is the interface between a CAN protocol controller and the physical bus. It is primarily intended for applications up to 1 MBd 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-circuits to positive and negative battery voltage. Although power dissipation will increase as a result of a short circuit fault condition, this feature will prevent destruction of the transmitter output stage. If the junction temperature exceeds approximately 160 C, the limiting current of both transmitter outputs is decreased. Because the transmitter is responsible for most of the power dissipated, this will result in reduced power dissipation and hence a lower chip temperature. All other parts of the IC will remain operational. The thermal protection is needed, in particular, 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. Pin 8 (Rs) allows three different modes of operation to be selected: High-speed, Slope control and 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 slopes. A shielded cable is recommended to avoid RFI problems. High-speed mode is selected by connecting pin 8 to ground. 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 slopes should be limited. The rise and fall slopes 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
PCA82C251
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 04 — 25 August 2011
3 of 17
NXP Semiconductors
PCA82C251
CAN transceiver for 24 V systems
LOW level. The microcontroller should react to this condition by switching the transceiver back to normal operation (via pin 8). Because the receiver is slower in Standby mode, the first message will be lost at higher bit rates.
Tab.