MCP2551

 2003 Microchip Technology Inc. DS21667D-page 1 M MCP2551 Features • Supports 1 Mb/s operation • Implements ISO-11898 standard physical layer requirements • Suitable for 12V and 24V systems • Externally-controlled slope for reduced RFI emissions • Detection of ground fault (permanent dominant) on TXD input • Power-on reset and voltage brown-out protection • An unpowered node or brown-out event will not disturb the CAN bus • Low current standby operation • Protection against damage due to short-circuit conditions (positive or negative battery voltage) • Protection against high-voltage transients • Automatic thermal shutdown protection • Up to 112 nodes can be connected • High noise immunity due to differential bus implementation • Temperature ranges: - Industrial (I): -40°C to +85°C - Extended (E): -40°C to +125°C Package Types Block Diagram RS CANH CANL VREF TXD VSS VDD RXD 1 2 3 4 8 7 6 5 PDIP/SOIC M C P2 55 1 Thermal Shutdown VDD VSS CANH CANL TXD RS RXD VREF VDD Slope Control Power-On Reset Reference Voltage Receiver GND 0.5 VDD TXD Dominant Detect Driver Control High-Speed CAN Transceiver 查询MCP2551供应商 MCP2551 DS21667D-page 2  2003 Microchip Technology Inc. NOTES:  2003 Microchip Technology Inc. DS21667D-page 3 MCP2551 1.0 DEVICE OVERVIEW The MCP2551 is a high-speed CAN, fault-tolerant device that serves as the interface between a CAN protocol controller and the physical bus. The MCP2551 provides differential transmit and receive capability for the CAN protocol controller and is fully compatible with the ISO-11898 standard, including 24V requirements. It will operate at speeds of up to 1 Mb/s. Typically, each node in a CAN system must have a device to convert the digital signals generated by a CAN controller to signals suitable for transmission over the bus cabling (differential output). It also provides a buffer between the CAN controller and the high-voltage spikes that can be generated on the CAN bus by outside sources (EMI, ESD, electrical transients, etc.). 1.1 Transmitter Function The CAN bus has two states: Dominant and Recessive. A dominant state occurs when the differential voltage between CANH and CANL is greater than a defined voltage (e.g.,1.2V). A recessive state occurs when the differential voltage is less than a defined voltage (typically 0V). The dominant and recessive states correspond to the low and high state of the TXD input pin, respectively. However, a dominant state initiated by another CAN node will override a recessive state on the CAN bus. 1.1.1 MAXIMUM NUMBER OF NODES The MCP2551 CAN outputs will drive a minimum load of 45Ω, allowing a maximum of 112 nodes to be connected (given a minimum differential input resistance of 20 kΩ and a nominal termination resistor value of 120Ω). 1.2 Receiver Function The RXD output pin reflects the differential bus voltage between CANH and CANL. The low and high states of the RXD output pin correspond to the dominant and recessive states of the CAN bus, respectively. 1.3 Internal Protection CANH and CANL are protected against battery short- circuits and electrical transients that can occur on the CAN bus. This feature prevents destruction of the transmitter output stage during such a fault condition. The device is further protected from excessive current loading by thermal shutdown circuitry that disables the output drivers when the junction temperature exceeds a nominal limit of 165°C. All other parts of the chip remain operational and the chip temperature is lowered due to the decreased power dissipation in the transmitter outputs. This protection is essential to protect against bus line short-circuit-induced damage. 1.4 Operating Modes The RS pin allows three modes of operation to be selected: • High-Speed • Slope-Control • Standby These modes are summarized in Table 1-1. When in High-speed or Slope-control mode, the drivers for the CANH and CANL signals are internally regu- lated to provide controlled symmetry in order to mini- mize EMI emissions. Additionally, the slope of the signal transitions on CANH and CANL can be controlled with a resistor connected from pin 8 (RS) to ground, with the slope proportional to the current output at RS, further reducing EMI emissions. 1.4.1 HIGH-SPEED High-speed mode is selected by connecting the RS pin to VSS. In this mode, the transmitter output drivers have fast output rise and fall times to support high-speed CAN bus rates. 1.4.2 SLOPE-CONTROL Slope-control mode further reduces EMI by limiting the rise and fall times of CANH and CANL. The slope, or slew rate (SR), is controlled by connecting an external resistor (REXT) between RS and VOL (usually ground). The slope is proportional to the current output at the RS pin. Since the current is primarily determined by the slope-control resistance value REXT, a certain slew rate is achieved by applying a respective resistance. Figure 1-1 illustrates typical slew rate values as a function of the slope-control resistance value. 1.4.3 STANDBY MODE The device may be placed in standby or “SLEEP” mode by applying a high-level to RS. In SLEEP mode, the transmitter is switched off and the receiver operates at a lower current. The receive pin on the controller side (RXD) is still functional but will operate at a slower rate. The attached microcontroller can monitor RXD for CAN bus activity and place the transceiver into normal operation via the RS pin (at higher bus rates, the first CAN message may be lost). MCP2551 DS21667D-page 4  2003 Microchip Technology Inc. TABLE 1-1: MODES OF OPERATION TABLE 1-2: TRANSCEIVER TRUTH TABLE FIGURE 1-1: SLEW RATE VS. SLOPE-CONTROL RESISTANCE VALUE Mode Current at Rs Pin Resulting Voltage at RS Pin Standby -IRS < 10 µA VRS > 0.75 VDD Slope-control 10 µA < -IRS < 200 µA 0.4 VDD < VRS < 0.6 VDD High-speed -IRS < 610 µA 0 < VRS < 0.3VDD VDD VRS TXD CANH CANL Bus State( 1) RXD( 1) 4.5V ≤ VDD ≤ 5.5V VRS < 0.75 VDD 0 HIGH LOW Dominant 0 1 or floating Not Driven Not Driven Recessive 1 VRS > 0.75 VDD X Not Driven Not Driven Recessive 1 VPOR < VDD < 4.5V (See Note 3) VRS < 0.75 VDD 0 HIGH LOW Dominant 0 1 or floating Not Driven Not Driven Recessive 1 VRS > 0.75 VDD X Not Driven Not Driven Recessive 1 0 < VDD < VPOR X X Not Driven/ No Load Not Driven/ No Load High Impedance X Note 1: If another bus node is transmitting a dominant bit on the CAN bus, then RXD is a logic ‘0’. 2: X = “don’t care”. 3: Device drivers will function, although outputs are not ensured to meet the ISO-11898 specification. 0 5 10 15 20 25 10 20 30 40 49 60 70 76 90 100 110 120 Resistance (kΩ) Sl ew R at e V/ uS  2003 Microchip Technology Inc. DS21667D-page 5 MCP2551 1.5 TXD Permanent Dominant Detection If the MCP2551 detects an extended low state on the TXD input, it will disable the CANH and CANL output drivers in order to prevent the corruption of data on the CAN bus. The drivers are disabled if TXD is low for more than 1.25 ms (minimum). This implies a maximum bit time of 62.5 µs (16 kb/s bus rate), allowing up to 20 consecutive transmitted dominant bits during a multiple bit error and error frame scenario. The drivers remain disabled as long as TXD remains low. A rising edge on TXD will reset the timer logic and enable the CANH and CANL output drivers. 1.6 Power-on Reset When the device is powered on, CANH and CANL remain in a high-impedance state until VDD reaches the voltage-level VPORH. In addition, CANH and CANL will remain in a high-impedance state if TXD is low when VDD reaches VPORH. CANH and CANL will become active only after TXD is asserted high. Once powered on, CANH and CANL will enter a high-impedance state if the voltage level at VDD falls below VPORL, providing voltage brown-out protection during normal operation. 1.7 Pin Descriptions The 8-pin pinout is listed in Table 1-3. TABLE 1-3: MCP2551 PINOUT 1.7.1 TRANSMITTER DATA INPUT (TXD) TXD is a TTL-compatible input pin. The data on this pin is driven out on the CANH and CANL differential output pins. It is usually connected to the transmitter data output of the CAN controller device. When TXD is low, CANH and CANL are in the dominant state. When TXD is high, CANH and CANL are in the recessive state, provided that another CAN node is not driving the CAN bus with a dominant state. TXD has an internal pull-up resistor (nominal 25 kΩ to VDD). 1.7.2 GROUND SUPPLY (VSS) Ground supply pin. 1.7.3 SUPPLY VOLTAGE (VDD) Positive supply voltage pin. 1.7.4 RECEIVER DATA OUTPUT (RXD) RXD is a CMOS-compatible output that drives high or low depending on the differential signals on the CANH and CANL pins and is usually connected to the receiver data input of the CAN controller device. RXD is high when the CAN bus is recessive and low in the dominant state. 1.7.5 REFERENCE VOLTAGE (VREF) Reference Voltage Output (Defined as VDD/2). 1.7.6 CAN LOW (CANL) The CANL output drives the low side of the CAN differential bus. This pin is also tied internally to the receive input comparator. 1.7.7 CAN HIGH (CANH) The CANH output drives the high-side of the CAN differential bus. This pin is also tied internally to the receive input comparator. 1.7.8 SLOPE RESISTOR INPUT (RS) The RS pin is used to select High-speed, Slope-control or Standby modes via an external biasing resistor. Pin Number Pin Name Pin Function 1 TXD Transmit Data Input 2 VSS Ground 3 VDD Supply Voltage 4 RXD Receive Data Output 5 VREF Reference Output Voltage 6 CANL CAN Low-Level Voltage I/O 7 CANH CAN High-Level Voltage I/O 8 RS Slope-Control Input MCP2551 DS21667D-page 6  2003 Microchip Technology Inc. NOTES:  2003 Microchip Technology Inc. DS21667D-page 7 MCP2551 2.0 ELECTRICAL CHARACTERISTICS 2.1 Terms and Definitions A number of terms are defined in ISO-11898 that are used to describe the electrical characteristics of a CAN transceiver device. These terms and definitions are summarized in this section. 2.1.1 BUS VOLTAGE VCANL and VCANH denote the voltages of the bus line wires CANL and CANH relative to ground of each individual CAN node. 2.1.2 COMMON MODE BUS VOLTAGE RANGE Boundary voltage levels of VCANL and VCANH with respect to ground, for which proper operation will occur, if up to the maximum number of CAN nodes are connected to the bus. 2.1.3 DIFFERENTIAL INTERNAL CAPACITANCE, CDIFF (OF A CAN NODE) Capacitance seen between CANL and CANH during the recessive state when the CAN node is disconnected from the bus (see Figure 2-1). 2.1.4 DIFFERENTIAL INTERNAL RESISTANCE, RDIFF (OF A CAN NODE) Resistance seen between CANL and CANH during the recessive state when the CAN node is disconnected from the bus (see Figure 2-1). 2.1.5 DIFFERENTIAL VOLTAGE, VDIFF (OF CAN BUS) Differential voltage of the two-wire CAN bus, value VDIFF = VCANH - VCANL. 2.1.6 INTERNAL CAPACITANCE, CIN (OF A CAN NODE) Capacitance seen between CANL (or CANH) and ground during the recessive state when the CAN node is disconnected from the bus (see Figure 2-1). 2.1.7 INTERNAL RESISTANCE, RIN (OF A CAN NODE) Resistance seen between CANL (or CANH) and ground during the recessive state when the CAN node is disconnected from the bus (see Figure 2-1). FIGURE 2-1: PHYSICAL LAYER DEFINITIONS RIN RIN RDIFF CIN CIN CDIFF CANL CANH GROUND ECU MCP2551 DS21667D-page 8  2003 Microchip Technology Inc. Absolute Maximum Ratings† VDD.............................................................................................................................................................................7.0V DC Voltage at TXD, RXD, VREF and VS ............................................................................................ -0.3V to VDD + 0.3V DC Voltage at CANH, CANL (Note 1) .......................................................................................................... -42V to +42V Transient Voltage on Pins 6 and 7 (Note 2) ............................................................................................. -250V to +250V Storage temperature ...............................................................................................................................-55°C to +150°C Operating ambient temperature ..............................................................................................................-40°C to +125°C Virtual Junction Temperature, TVJ (Note 3).............................................................................................-40°C to +150°C Soldering temperature of leads (10 seconds) .......................................................................................................+300°C ESD protection on CANH and CANL pins (Note 4) ...................................................................................................6 kV ESD protection on all other pins (Note 4) ..................................................................................................................4 kV Note 1: Short-circuit applied when TXD is high and low. 2: In accordance with ISO-7637. 3: In accordance with IEC 60747-1. 4: Classification A: Human Body Model. † NOTICE: Stresses above those listed under “Maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.  2003 Microchip Technology Inc. DS21667D-page 9 MCP2551 2.2 DC Characteristics DC Specifications Electrical Characteristics: Industrial (I): TAMB = -40°C to +85°C VDD = 4.5V to 5.5V Extended (E):TAMB = -40°C to +125°C VDD = 4.5V to 5.5V Param No. Sym Characteristic Min Max Units Conditions Supply D1 IDD Supply Current — 75 mA Dominant; VTXD = 0.8V; VDD D2 — 10 mA Recessive; VTXD = +2V; RS = 47 kΩ D3 — 365 µA -40°C ≤ TAMB ≤ +85°C, Standby; (Note 2) — 465 µA -40°C ≤ TAMB ≤ +125°C, Standby; (Note 2) D4 VPORH High-level of the power-on reset comparator 3.8 4.3 V CANH, CANL outputs are active when VDD > VPORH D5 VPORL Low-level of the power-on reset comparator 3.4 4.0 V CANH, CANL outputs are not active when VDD < VPORL D6 VPORD Hysteresis of power-on reset comparator 0.3 0.8 V Note 1 Bus Line (CANH; CANL) Transmitter D7 VCANH(r);VCANL(r) CANH, CANL Recessive bus voltage 2.0 3.0 V VTXD = VDD; no load. D8 IO(CANH)(reces) IO(CANL)(reces) Recessive output current -2 +2 mA -2V < V(CAHL,CANH) < +7V, 0V