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PCA82C250 データシート(PDF) 4 Page - NXP Semiconductors |
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PCA82C250 データシート(HTML) 4 Page - NXP Semiconductors |
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4 / 20 page  2000 Jan 13 4 Philips Semiconductors Product specification CAN controller interface PCA82C250 FUNCTIONAL DESCRIPTION The PCA82C250 is the interface between the CAN protocol controller and the physical bus. It is primarily intended for high-speed applications (up to 1 Mbaud) in cars. 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 a reduced power dissipation and hence a lower chip temperature. All other parts of the IC will remain in operation. 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. 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. 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 LOW level. The microcontroller should react to this condition by switching the transceiver back to normal operation (via pin 8). Because the receiver is slow in standby mode, the first message will be lost. Table 1 Truth table of the CAN transceiver Note 1. X = don’t care. Table 2 Pin Rs summary SUPPLY TXD CANH CANL BUS STATE RXD 4.5 to 5.5 V 0 HIGH LOW dominant 0 4.5 to 5.5 V 1 (or floating) floating floating recessive 1 <2 V (not powered) X(1) floating floating recessive X(1) 2V<VCC < 4.5 V >0.75VCC floating floating recessive X(1) 2V<VCC < 4.5 V X(1) floating if VRs > 0.75VCC floating if VRs > 0.75VCC recessive X(1) CONDITION FORCED AT PIN Rs MODE RESULTING VOLTAGE OR CURRENT AT PIN Rs VRs > 0.75VCC standby IRs < 10 µA −10 µA<I Rs < −200 µA slope control 0.4VCC <VRs < 0.6VCC VRs < 0.3VCC high-speed IRs < −500 µA |
同様の部品番号 - PCA82C250 |
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同様の説明 - PCA82C250 |
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