PCA82C250(2009) Ver la hoja de datos (PDF) - NXP Semiconductors.
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PCA82C250 Datasheet PDF : 17 Pages
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NXP Semiconductors
PCA82C250
CAN controller interface
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 PCA82C250 is the interface between a CAN protocol controller and the physical bus.
It is primarily intended for high-speed automotive applications (up to 1 MBd). 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” 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 reduced power dissipation and hence a
lower chip temperature. All other parts of the PCA82C250 will remain in operation. 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 slope.
Use of a shielded cable is recommended to avoid RFI problems. The High-speed mode is
selected by connecting pin 8 to ground.
For lower speeds or shorter bus length, an unshielded twisted pair or a parallel pair of
wires can be used for the bus. 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
PCA82C250_6
Product data sheet
Rev. 06 — 26 March 2009
© NXP B.V. 2009. All rights reserved.
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