ISL4485--5V供电485接口

1 ® ISL4485E CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2004, 2005. All Rights Reserved. All other trademarks mentioned are the property of their respective owners. FN6049.3 ±15kV ESD Protected, 20Mbps, 5V, Low Power, RS-485/RS-422 Transceiver The Intersil ISL4485E is a high speed, BiCMOS 5V powered, single transceiver that meets both the RS-485 and RS-422 standards for balanced communication. Each driver output/receiver input is protected against ±15kV ESD strikes, without latch-up. Unlike competitive devices, this Intersil device is specified for 10% tolerance supplies (4.5V to 5.5V). The excellent differential output voltage coupled with high drive-current output stages allow 20Mbps operation over twisted pair networks up to 450 feet in length. The 25kΩ receiver input resistance presents a “single unit load” to the RS-485 bus, allowing up to 32 transceivers on the network. Receiver (Rx) inputs feature a “fail-safe if open” design, which ensures a logic high Rx output if Rx inputs are floating. Driver (Tx) outputs are short circuit protected, even for voltages exceeding the power supply voltage. Additionally, on-chip thermal shutdown circuitry disables the Tx outputs to prevent damage if power dissipation becomes excessive. The half duplex configuration multiplexes the Rx inputs and Tx outputs to allow transceivers with Rx and Tx disable functions in 8 lead packages. Features • Pb-Free Available (RoHS Compliant) • High Data Rates. . . . . . . . . . . . . . . . . . . . . up to 20Mbps • RS-485 I/O Pin ESD Protection . . . . . . . . . . ±15kV HBM - Class 3 ESD Level on all Other Pins . . . . . . >7kV HBM • Operates from a Single +5V Supply (10% Tolerance) • 1 Unit Load Allows up to 32 Devices on the Bus • Low Quiescent Current . . . . . . . . . . . . . . . . . . . . . 700µA • -7V to +12V Common Mode Input Voltage Range • Three State Rx and Tx Outputs • 30ns Propagation Delays, 2ns Skew • Current Limiting and Thermal Shutdown for driver Overload Protection Applications • SCSI “Fast 20” Drivers and Receivers • Data Loggers • Security Networks • Building Environmental Control Systems • Industrial/Process Control Networks • Level Translators Pinout ISL4485E (SOIC) TOP VIEW Ordering Information PART NO. (BRAND) TEMP. RANGE (oC) PACKAGE PKG. DWG. # ISL4485EIB (4485EIB) -40 to 85 8 Ld SOIC M8.15 ISL4485EIBZ (4485EIBZ) (See Note) -40 to 85 8 Ld SOIC (Pb-free) M8.15 ISL4485EIB-T (4485EIB) -40 to 85 8 Ld SOIC Tape & Reel M8.15 ISL4485EIBZ-T (4485EIBZ) (See Note) -40 to 85 8 Ld SOIC Tape & Reel (Pb-free) M8.15 NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. RO RE DE DI 1 2 3 4 8 7 6 5 VCC B / Z A / Y GNDD R Data Sheet April 21, 2005 ISL4485E Truth Tables TRANSMITTING INPUTS OUTPUTS RE DE DI B/Z A/Y X 1 1 0 1 X 1 0 1 0 X 0 X High-Z High-Z RECEIVING INPUTS OUTPUT RE DE A-B RO 0 0 ≥ +0.2V 1 0 0 ≤ -0.2V 0 0 0 Inputs Open 1 1 X X High-Z Pin Descriptions PIN FUNCTION RO Receiver output: If A > B by at least 0.2V, RO is high; If A < B by 0.2V or more, RO is low; RO = High if A and B are unconnected (floating). RE Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE is high. DE Driver output enable. The driver outputs, Y and Z, are enabled by bringing DE high. They are high impedance when DE is low. DI Driver input. A low on DI forces output Y low and output Z high. Similarly, a high on DI forces output Y high and output Z low. GND Ground connection. A/Y ±15kV HBM ESD Protected, noninverting receiver input and noninverting driver output. Pin is an input (A) if DE = 0; pin is an output (Y) if DE = 1. B/Z ±15kV HBM ESD Protected, inverting receiver input and inverting driver output. Pin is an input (B) if DE = 0; pin is an output (Z) if DE = 1. VCC System power supply input (4.5V to 5.5V). Typical Operating Circuit 0.1µF+ D R 7 6 8 1 2 3 4 5 VCC GND RO RE DE DI A/Y B/Z +5V 0.1µF + D R 6 7 8 1 2 3 4 5 VCC GND RO RE DE DI A/Y B/Z +5V RT RT ISL4485E 2 ISL4485E Absolute Maximum Ratings Thermal Information VCC to Ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7V Input Voltages DI, DE, RE . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to (VCC +0.5V) Input / Output Voltages A / Y, B / Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -8V to +12.5V RO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to (VCC +0.5V) Short Circuit Duration Y, Z. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . See Specification Table Operating Conditions Temperature Range ISL4485EIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40oC to 85oC Thermal Resistance (Typical, Note 1) θJA (oC/W) 8 Ld SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . 170 Maximum Junction Temperature (Plastic Package) . . . . . . . 150oC Maximum Storage Temperature Range . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC (Lead Tips Only) CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTE: 1. θJA is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details. Electrical Specifications Test Conditions: VCC = 4.5V to 5.5V; Unless Otherwise Specified. Typicals are at VCC = 5V, TA = 25 oC, Note 2 PARAMETER SYMBOL TEST CONDITIONS TEMP (oC) MIN TYP MAX UNITS DC CHARACTERISTICS Driver Differential VOUT (no load) VOD1 Full - - VCC V Driver Differential VOUT (with load) VOD2 R = 50Ω (RS-422), (Figure 1) Full 2 3 - V R = 27Ω (RS-485), (Figure 1) Full 1.5 2.3 5 V Change in Magnitude of Driver Differential VOUT for Complementary Output States ∆VOD R = 27Ω or 50Ω, (Figure 1) Full - 0.01 0.2 V Driver Common-Mode VOUT VOC R = 27Ω or 50Ω, (Figure 1) Full - - 3 V Change in Magnitude of Driver Common-Mode VOUT for Complementary Output States ∆VOC R = 27Ω or 50Ω, (Figure 1) Full - 0.01 0.2 V Logic Input High Voltage VIH DE, DI, RE Full 2 - - V Logic Input Low Voltage VIL DE, DI, RE Full - - 0.8 V Logic Input Current IIN1 DE, DI, RE Full -25 - 25 µA Input Current (A, B), (Note 5) IIN2 DE = 0V, VCC = 0V or 4.5 to 5.5V VIN = 12V Full - - 1 mA VIN = -7V Full - - -0.8 mA Receiver Differential Threshold Voltage VTH -7V ≤ VCM ≤ 12V Full -0.2 - 0.2 V Receiver Input Hysteresis ∆VTH VCM = 0V 25 - 70 - mV Receiver Output High Voltage VOH IO = -4mA, VID = 200mV Full 3.5 4 - V Receiver Output Low Voltage VOL IO = -4mA, VID = 200mV Full - 0.1 0.4 V Three-State (high impedance) Receiver Output Current IOZR 0.4V ≤ VO ≤ 2.4V Full - - ±1 µA Receiver Input Resistance RIN -7V ≤ VCM ≤ 12V Full 12 25 - kΩ No-Load Supply Current, (Note 3) ICC DI, RE = 0V or VCC DE = VCC Full - 700 900 µA DE = 0V Full - 500 565 µA Driver Short-Circuit Current, VO = High or Low IOSD1 DE = VCC, -7V ≤ VY or VZ ≤ 12V, (Note 4) Full 35 - 250 mA Receiver Short-Circuit Current IOSR 0V ≤ VO ≤ VCC Full 7 - 85 mA 3 ISL4485E SWITCHING CHARACTERISTICS Driver Input to Output Delay tPLH, tPHL RDIFF = 54Ω, CL = 100pF, (Figure 2) Full 15 30 50 ns Driver Output Skew tSKEW RDIFF = 54Ω, CL = 100pF, (Figure 2) Full - 1.3 5 ns Driver Differential Rise or Fall Time tR, tF RDIFF = 54Ω, CL = 100pF, (Figure 2) Full 3 11 25 ns Driver Enable to Output High tZH CL = 100pF, SW = GND, (Figure 3) Full - 17 30 ns Driver Enable to Output Low tZL CL = 100pF, SW = VCC, (Figure 3) Full - 14 30 ns Driver Disable from Output High tHZ CL = 15pF, SW = GND, (Figure 3) Full - 19 30 ns Driver Disable from Output Low tLZ CL = 15pF, SW = VCC, (Figure 3) Full - 13 30 ns Driver Maximum Data Rate fMAXD VOD ≥ 1.5V , (Figure 4, Note 6) Full 20 - - Mbps Receiver Input to Output Delay tPLH, tPHL Figure 5 Full 20 40 70 ns Receiver Skew | tPLH - tPHL | tSKD Figure 5 Full - 3 10 ns Receiver Enable to Output High tZH CL = 15pF, SW = GND, (Figure 6) Full - 9 25 ns Receiver Enable to Output Low tZL CL = 15pF, SW = VCC, (Figure 6) Full - 9 25 ns Receiver Disable from Output High tHZ CL = 15pF, SW = GND, (Figure 6) Full - 9 25 ns Receiver Disable from Output Low tLZ CL = 15pF, SW = VCC, (Figure 6) Full - 9 25 ns Receiver Maximum Data Rate fMAXR CL = 15pF, VID ≥ 1.5V (Note 6) Full 20 - - Mbps ESD PERFORMANCE RS-485 Pins (A/Y, B/Z) Human Body Model 25 - ±15 - kV All Other Pins 25 - >±7 - kV NOTE: 2. All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. 3. Supply current specification is valid for loaded drivers when DE = 0V. 4. Applies to peak current. See “Typical Performance Curves” for more information. 5. Devices meeting these limits are denoted as “single unit load (1 UL)” transceivers. The RS-485 standard allows up to 32 Unit Loads on the bus. 6. Guaranteed by characterization, but not tested. Test Circuits and Waveforms FIGURE 1. DRIVER VOD AND VOC Electrical Specifications Test Conditions: VCC = 4.5V to 5.5V; Unless Otherwise Specified. Typicals are at VCC = 5V, TA = 25 oC, Note 2 (Continued) PARAMETER SYMBOL TEST CONDITIONS TEMP (oC) MIN TYP MAX UNITS D DE DI VCC VOD VOC R R Z Y 4 ISL4485E FIGURE 2A. TEST CIRCUIT FIGURE 2B. MEASUREMENT POINTS FIGURE 2. DRIVER PROPAGATION DELAY AND DIFFERENTIAL TRANSITION TIMES FIGURE 3A. TEST CIRCUIT FIGURE 3B. MEASUREMENT POINTS FIGURE 3. DRIVER ENABLE AND DISABLE TIMES Test Circuits and Waveforms (Continued) D DE DI VCC SIGNAL GENERATOR CL = 100pF RDIFF Z Y CL = 100pF OUT (Y) 3V 0V tPLH 1.5V1.5V VOH VOL 50% 50% tPHL OUT (Z) tPHL VOH VOL 50% 50% tPLH DIFF OUT (Y - Z) tR +VOD -VOD 90% 90% tF 10% 10% DI SKEW = |CROSSING PT. OF Y↑ & Z↓ - CROSSING PT. OF Y↓ & Z↑| D DE DI CL 500ΩZ Y VCC GNDSW PARAMETER OUTPUT RE DI SW CL (pF) tHZ Y/Z X 1/0 GND 15 tLZ Y/Z X 0/1 VCC 15 tZH Y/Z X 1/0 GND 100 tZL Y/Z X 0/1 VCC 100 SIGNAL GENERATOR OUT (Y, Z) 3V 0V 1.5V1.5V VOH 0V 2.3V VOH - 0.5V tHZ OUT (Y, Z) VCC VOL 2.3V VOL + 0.5V tLZ DE OUTPUT HIGH OUTPUT LOW tZL tZH 5 ISL4485E FIGURE 4A. TEST CIRCUIT FIGURE 4B. MEASUREMENT POINTS FIGURE 4. DRIVER DATA RATE FIGURE 5A. TEST CIRCUIT FIGURE 5B. MEASUREMENT POINTS FIGURE 5. RECEIVER PROPAGATION DELAY FIGURE 6A. TEST CIRCUIT FIGURE 6B. MEASUREMENT POINTS FIGURE 6. RECEIVER ENABLE AND DISABLE TIMES Test Circuits and Waveforms (Continued) D DE DI VCC SIGNAL GENERATOR Z Y CD = 200pF VOD + - 60Ω 3V 0V DIFF OUT (Y - Z) +VOD -VOD DI 0V SIGNAL GENERATOR R RO RE A B+1.5V 15pF RO 3V 0V tPLH 1.5V1.5V VCC 0V 50% 50% tPHL A 1kΩ VCC GNDSW PARAMETER DE A SW tHZ 0 +1.5V GND tLZ 0 -1.5V VCC tZH 0 +1.5V GND tZL 0 -1.5V VCC SIGNAL GENERATOR R RO RE A B 15pF RO 3V 0V 1.5V1.5V VOH 0V 1.5V VOH - 0.5V tHZ RO VCC VOL 1.5V VOL + 0.5V tLZ RE OUTPUT HIGH OUTPUT LOW tZL tZH 6 ISL4485E Application Information RS-485 and RS-422 are differential (balanced) data transmission standards for use in long haul or noisy environments. RS-422 is a subset of RS-485, so RS-485 transceivers are also RS-422 compliant. RS-422 is a point- to-multipoint (multidrop) standard, which allows only one driver and up to 10 (assuming one unit load devices) receivers on each bus. RS-485 is a true multipoint standard, which allows up to 32 one unit load devices (any combination of drivers and receivers) on each bus. To allow for multipoint operation, the RS-485 spec requires that drivers must handle bus contention without sustaining any damage. Another important advantage of RS-485 is the extended common mode range (CMR), which specifies that the driver outputs and receiver inputs withstand signals that range from +12V to -7V. RS-422 and RS-485 are intended for runs as long as 4000’, so the wide CMR is necessary to handle ground potential differences, as well as voltages induced in the cable by external fields. Receiver Features The ISL4485E utilizes a differential input receiver for maximum noise immunity and common mode rejection. Input sensitivity is ±200mV, as required by the RS-422 and RS-485 specifications. Receiver input impedance surpasses the RS-422 spec of 4kΩ, and meets the RS-485 “Unit Load” requirement of 12kΩ minimum. Receiver inputs function with common mode voltages as great as ±7V outside the power supplies (i.e., +12V and -7V), making them ideal for long networks where induced voltages are a realistic concern. The receiver includes a “fail-safe if open” function that guarantees a high level receiver output if the receiver inputs are unconnected (floating). The output is three-statable via the active low RE input, and the receiver easily meets the 20Mbps data rate. Driver Features The RS-485/422 driver is a differential output device that delivers at least 1.5V across a 54Ω load (RS-485), and at least 2V across a 100Ω load (RS-422). The ISL4485E driver features low propagation delay skew to maximize bit width, and to minimize EMI, and the outputs are three-statable via the active high DE input. Outputs of ISL4485E drivers are not slew rate limited, so faster output transition times allow data rates up to 20Mbps. Data Rate, Cables, and Terminations Twisted pair is the cable of choice for RS-485/422 networks. Twisted pair cables tend to pick up noise and other electromagnetically induced voltages as common mode signals, which are effectively rejected by the differential receivers in these ICs. RS-485/422 are intended for network lengths up to 4000', but the maximum transmission length decreases as the data rate increases. According to guidelines in the RS-422 specification, a 20Mbps network should be limited to less than 50' of 24 AWG twisted pair. Nevertheless, the ISL4485E's large differential voltage swing, fast transition times, and high drive-current output stages allow operation at 20Mbps in RS-485/422 networks as long as 450'. Figure 7 details ISL4485E operation at 20Mbps driving 300' of CAT 5 cable terminated in 120Ω at the driver and the receiver (i.e., double terminated). The acceptance criteria for this test was the ability of the driver to deliver a 1.5V differential signal to the receiver at the end of the cable (i.e., |A-B| ≥ 1.5V). If a more liberal acceptance criteria is used, the distance can be further extended. For example, Figure 8 illustrates the performance in the same configuration, but with a cable length of 450', and an acceptance criteria of no more than 6dB attenuation across the cable (i.e., |A-B| = |Y-Z|/2). Driver differential output voltage decreases with increasing differential load capacitance, so maintaining a 1.5V differential output requires a data rate reduction, as shown in Figure 9. To minimize reflections, proper termination is imperative when using this 20Mbps device. In point-to-point, or point-to- multipoint (single driver on bus) networks, the main cable should be terminated in its characteristic impedance (typically 120Ω) at the end farthest from the driver. In multi- receiver applications, stubs connecting receivers to the main cable should be kept as short as possible (preferably less than 12 inches). Multipoint (multi-driver) systems require that the main cable be terminated in its characteristic impedance at both ends. Again, stubs connecting a transceiver to the main cable should be kept as short as possible. Built-In Driver Overload Protection As stated previously, the RS-485 spec requires that drivers survive worst case bus contentions undamaged. The ISL4485E device meets this requirement via driver output short circuit current limits, and on-chip thermal shutdown circuitry. The driver output stages incorporate short circuit current limiting circuitry which ensures that the output current never exceeds the RS-485 spec, even at the common mode voltage range extremes. Additionally, these devices utilize a foldback circuit which reduces the short circuit current, and thus the power dissipation, whenever the contending voltage exceeds either supply. In the event of a major short circuit condition, this device also includes a thermal shutdown feature that disables the drivers whenever the die temperature becomes excessive. This eliminates the power dissipation, allowing the die to cool. The drivers automatically reenable after the die 7 ISL4485E temperature drops about 15 degrees. If the contention persists, the thermal shutdown / reenable cycle repeats until the fault is cleared. Receivers stay operational during thermal shutdown. ESD Protection All pins on these interface devices include class 3 Human Body Model (HBM) ESD protection structures, but the RS-485 pins (driver outputs and receiver inputs) incorporate advanced structures allowing them to survive ESD events in excess of ±15kV HBM. The RS-485 pins are particularly vulnerable to ESD damage because they typically connect to an exposed port on the exterior of the finished product. Simply touching the port pins, or connecting a cable, can cause an ESD event that might destroy unprotected ICs. These new ESD structures protect the device whether or not it is powered up, protect without allowing any latchup mechanism to activate, and without degrading the RS-485 common mode range of -7V to +12V. This built-in ESD protection eliminates the need for board level protection structures (e.g., transient suppression diodes), and the associated, undesirable capacitive load they present. Human Body Model Testing As the name implies, this test method emulates the ESD event delivered to an IC during human handling. The tester delivers the charge stored on a 100pF capacitor through a 1.5kΩ current limiting resistor into the pin under test. The HBM method determines an ICs ability to withstand the ESD events typically present during handling and manufacturing. The RS-485 pin survivability on this high ESD device has been characterized to be in excess of ±15kV, for discharges to GND. Typical Performance Curves VCC = 5V, TA = 25oC; Unless Otherwise Specified FIGURE 7. DRIVER AND RECEIVER WAVEFORMS DRIVING 300 FEET OF CABLE (DOUBLE TERMINATED) FIGURE 8. DRIVER AND RECEIVER WAVEFORMS DRIVING 450 FEET OF CABLE (DOUBLE TERMINATED) FIGURE 9. DATA RATE vs DIFFERENTIAL CAPACITANCE FIGURE 10. SUPPLY CURRENT vs TEMPERATURE TIME (20ns/DIV) -3 R E C E IV E R O U TP U T (V ) 1.5 3 -1.5 0 A - B 0 5 R E C E IV E R IN P U T (V ) 0 5 D R IV E R IN P U T (V ) DI RO DRIVER+CABLE DELAY (~450ns) TIME (20ns/DIV) -3 R E C E IV E R O U TP U T (V ) 1.5 3 -1.5 0 A - B 0 5 R E C E IV E R IN P U T (V ) 0 5 D R IV E R IN P U T (V ) DI RO DRIVER+CABLE DELAY (~650ns) DIFFERENTIAL CAPACITANCE (pF) D A TA R A TE (M bp s) 5001000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 5 10 15 20 25 30 RDIFF = 54Ω -40 0 50 85 TEMPERATURE (oC) I C C (µ A ) -25 25 75 400 450 500 550 60