MAX14780E +5.0V, ±30kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver

Transcription

1 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, General Description The MX1478E is a +5V, ±3kV HM ESD half duplex S-485/422 transceiver. The MX1478E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 5kbps. The MX1478E is available in an 8-pin SO and PP packages operating over a temperature range from -4 C to +85 C. Utility Meters Lighting Systems Industrial Control Telecom Security Systems Instrumentation pplications enefits and Features Integrated Protection Increases obustness S ±3kV HM ESD per JEC JS S ±12kV Contact ESD per IEC S ±15kV ir Gap ESD per IEC S True Fail-Safe eceiver Prevents False Transitions on eceiver Input Short or Open S Hot Swap Eliminates False Transitions During Power-Up or Hot Insertion S Short-Circuit Protected Outputs Low Current educes Power Consumption Low Current educes Power Consumption S 1µ Shutdown Current S 1.2m of Supply Current When Unloaded Ordering Information PT TEMP NGE PIN-PCKGE MX1478EES+ -4NC to +85NC 8 SO MX1478EEP+ -4NC to +85NC 8 PP +Denotes a lead(pb)-free/ohs-compliant package. Typical Operating Circuit D GND.1µF t MX1478E t D TYPICL HLF-DUPLEX OPETING CICUIT For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at ; ev 3; 1/15

2 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, SOLUTE MXIMUM TINGS (ll voltages referenced to GND.) Supply Voltage ( )... +6V Control Input Voltage (, )...-.3V to +6V Driver Input Voltage ()...-.3V to +6V Driver Output Voltage (, )...-8V to +13V eceiver Input Voltage (, )...-8V to +13V eceiver Output Voltage () V to ( +.3V) Driver Output Current... ±25m Continuous Power Dissipation (T = +7 C) SO (derate 5.9mW/ C above +7 C)...471mW PP (derate 9.1mW/ C above +7 C) mW Operating Temperature ange C to +85 C Junction Temperature C Storage Temperature ange C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) C Stresses beyond those listed under bsolute Maximum atings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC ELECTICL CHCTEISTICS ( = +5.V ±1%, T = T MIN to T MX, unless otherwise noted. Typical values are at = +5.V and T = +25NC.) (Note 1) DIVE PMETE SYMOL CONTIONS MIN TYP MX UNITS Supply-Voltage ange V L = 1I (S-422), Figure 1 3 Differential Driver Output V OD L = 54I (S-485), Figure 1 2 V No load Change in Magnitude of Differential Output Voltage Driver Common-Mode Output Voltage Change in Magnitude of Common-Mode Voltage DV OD L = 1I or 54I, Figure 1 (Note 2).2 V V OC L = 1I or 54I, Figure 1 /2 3 V DV OC L = 1I or 54I, Figure 1 (Note 2).2 V Input-High Voltage V IH,, 3 V Input-Low Voltage V IL,,.8 V Input Hysteresis V HYS,, 1 mv Input Current I IN1,, Q1 F Input Impedance First Transition at Power-Up Input Impedance on First Transition after PO Delay Driver Short-Circuit Output Current Driver Short-Circuit Foldback Output Current PWUP, = = 2V ki ft = = 2V 7 6 kω P V OUT P +12V (Note 3) 4 25 I OSD -7V P V OUT P (Note 3) ( - 1V) P V OUT P +12V (Note 3) 2 I OSDF -7V P V OUT P +1V (Note 3) -2 Thermal-Shutdown Threshold T TS 175 NC Thermal-Shutdown Hysteresis T TSH 15 NC V = V, V IN = +12V 125 Input Current ( and ) I, = V or V IN = -7V -1 CEIVE eceiver Differential Threshold Voltage V TH -7V P VCM P +12V mv eceiver Input Hysteresis DV TH V + V = V 15 mv 2 Maxim Integrated m m F

3 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, DC ELECTICL CHCTEISTICS (continued) ( = +5.V ±1%, T = T MIN to T MX, unless otherwise noted. Typical values are at = +5.V and T = +25NC.) (Note 1) PMETE SYMOL CONTIONS MIN TYP MX UNITS Output-High Voltage V OH I O = -1m Output-Low Voltage V OL I O = 1m.4 V Three-State Output Current at eceiver -.6 I OZ P VO P P 1 F eceiver Input esistance IN -7V P VCM P +12V 96 ki eceiver Output Short-Circuit Current SUPPLY CUNT I OS V P V P P 11 m Supply Current I CC No load, =, = No load, V = V, = Supply Current in Shutdown Mode ESD PTECTION ESD Protection for and No load, V = V, V = V I SHDN = VCC, V = V F Human ody Model Contact Discharge IEC ir-gap Discharge IEC Q3 Q12 Q15 V m kv DIVE SWITCHING CHCTEISTICS WITH INTENL SL (5kbps) ( = +5.V ±1%, T = T MIN to T MX, unless otherwise noted. Typical values are at = +5.V and T = +25NC.) (Note 1) PMETE SYMOL CONTIONS MIN TYP MX UNITS Driver Propagation Delay Driver Differential Output ise or Fall Time Differential Driver Output Skew t DPLH - t DPHL t DPLH 2 1 C L = 5pF, L = 54I, Figures 2 and 3 t DPHL 2 1 t, t F CL = 5pF, L = 54I, Figures 2 and ns t DSKEW CL = 5pF, L = 54I, Figures 2 and 3 14 ns Maximum Data ate 5 kbps Driver Enable to Output High t DZH Figure 4 25 ns Driver Enable to Output Low t DZL Figure 5 25 ns Driver Disable Time from Low t DLZ Figure 5 1 ns Driver Disable Time from High t DHZ Figure 4 1 ns Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low t DZH(SHDN) Figure 4 55 ns t DZL(SHDN) Figure 5 55 ns Time to Shutdown t SHDN ns ns Maxim Integrated 3

4 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, CEIVE SWITCHING CHCTEISTICS WITH INTENL SL (5kbps) ( = +5.V ±1%, T = T MIN to T MX, unless otherwise noted. Typical values are at = +5.V and T = +25NC.) (Note 1) PMETE SYMOL CONTIONS MIN TYP MX UNITS eceiver Propagation Delay eceiver Output Skew t PLH - t PHL t PLH 2 C L = 15pF, Figures 6 and 7 t PHL 2 t SKEW C L = 15pF, Figures 6 and 7 3 ns Maximum Data ate 5 kbps eceiver Enable to Output Low t ZL Figure 8 5 ns eceiver Enable to Output High t ZH Figure 8 5 ns eceiver Disable Time from Low t LZ Figure 8 5 ns eceiver Disable Time from High t HZ Figure 8 5 ns eceiver Enable from Shutdown to Output High eceiver Enable from Shutdown to Output Low t ZH(SHDN) Figure 8 55 ns t ZL(SHDN) Figure 8 55 ns Time to Shutdown t SHDN ns Note 1: ll currents into the device are positive. ll currents out of the device are negative. ll voltages are referred to device ground, unless otherwise noted. Note 2: ΔV OD and ΔV OC are the changes in V OD and V OC, respectively, when the input changes state. Note 3: The short-circuit output current applies to peak current just prior to foldback current limiting. The short-circuit foldback output current applies during current limiting to allow a recovery from bus contention. ns Test Circuits and Waveforms V OD L /2 /2 t DPLH t DPHL 1/2 V O Figure 1. Driver DC Test Load L /2 V OC V FF Z Y V O -V O V O 1/2 V O 1% t V FF = V () - V () 9% 9% t F 1% t SKEW = t DPLH - t DPHL V OD L CL Figure 3. Driver Propagation Delays Figure 2. Driver Timing Test Circuit 4 Maxim Integrated

5 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, Test Circuits and Waveforms (continued) S1 O D OUT C L 5pF L = 5Ω GENETO 5Ω t DZH, t DZH(SHDN) /2.25V V OH OUT V OM = ( + V OH )/2 t DHZ Figure 4. Driver Enable and Disable Times (t DHZ, t DZH, t DZH(SHDN) ) S1 O D L = 5Ω OUT C L 5pF GENETO 5Ω t DZL, t DZL(SHDN) /2 OUT V OM = (V OL + )/2 V OL.25V t DLZ Figure 5. Driver Enable and Disable Times (t DZL, t DLZ, t DLZ(SHDN) ) Maxim Integrated 5

6 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, Test Circuits and Waveforms (continued) +1V TE V ID CEIVE OUTPUT t PLH V OH V /2 OL THE ISE TIME ND FLL TIME OF INPUTS ND < 4ns t PHL -1V Figure 6. eceiver Propagation Delay Test Circuit Figure 7. eceiver Propagation Delays +1.5V -1.5V S3 V ID 1kΩ S1 C L 15pF S2 GENETO 5Ω S1 OPEN S2 CLOSED V S3 = +1.5V S1 CLOSED S2 OPEN V S3 = -1.5V /2 t ZH, t ZH(SHDN) t ZL, t ZL(SHDN) V OH V OH / 2 (V OL + )/2 V OL S1 OPEN S2 CLOSED V S3 = +1.5V S1 CLOSED S2 OPEN V S3 = -1.5V 5% /2 5% t HZ /2 t LZ.25V 1% V OH 1%.25V V OL Figure 8. eceiver Enable and Disable Times 6 Maxim Integrated

7 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, ( = +5.V, T = +25 C, unless otherwise noted.) Typical Operating Characteristics SUPPLY CUNT (m) SUPPLY CUNT vs. TEMPETU NO LOD = = MX1478E toc1 OUTPUT CUNT (m) OUTPUT CUNT vs. CEIVE OUTPUT-HIGH VOLTGE MX1478E toc2 OUTPUT CUNT (m) OUTPUT CUNT vs. CEIVE OUTPUT-LOW VOLTGE MX1478E toc TEMPETU ( C) OUTPUT HIGH VOLTGE (V) OUTPUT LOW VOLTGE (V) OUTPUT HIGH VOLTGE (V) CEIVE OUTPUT-HIGH VOLTGE vs. TEMPETU I O = -1m MX1478E toc4 OUTPUT LOW VOLTGE (V) CEIVE OUTPUT-LOW VOLTGE vs. TEMPETU I O = 1m MX1478E toc5 FFENTIL OUTPUT CUNT (m) DIVE FFENTIL OUTPUT CUNT vs. FFENTIL OUTPUT VOLTGE MX1478E toc TEMPETU ( C) TEMPETU ( C) FFENTIL OUTPUT VOLTGE (V) FFENTIL OUTPUT VOLTGE (V) DIVE FFENTIL OUTPUT VOLTGE vs. TEMPETU L = 54Ω MX1478E toc7 OUTPUT CUNT (m) OUTPUT CUNT vs. TNSMITTE OUTPUT-HIGH VOLTGE MX1478E toc8 OUTPUT CUNT (m) OUTPUT CUNT vs. TNSMITTE OUTPUT-LOW VOLTGE MX1478E toc TEMPETU ( C) OUTPUT HIGH VOLTGE (V) OUTPUT-LOW VOLTGE (V) Maxim Integrated 7

8 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, Typical Operating Characteristics (continued) ( = +5.V, T = +25 C, unless otherwise noted.) SHUTDOWN CUNT (µ) SHUTDOWN CUNT vs. TEMPETU MX1478E toc1 DIVE PPGTION LY (ns) DIVE PPGTION LY vs. TEMPETU (5kbps) t DPHL t DPLH MX1478E toc11 CEIVE PPGTION LY (ns) CEIVE PPGTION LY vs. TEMPETU (5kbps) t DPLH t DPHL MX1478E toc TEMPETU ( C) TEMPETU ( C) TEMPETU ( C) CEIVE PPGTION LY (5kbps) MX1478E toc13 L = 1 V - V 5V/div DIVE PPGTION LY (5kbps) MX1478E toc14 L = 1 2V/div 2V/div V Y - V Z 5V/div 2ns/ div 4ns/ div 8 Maxim Integrated

9 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, Pin Configuration D 5 GND SO/PP Pin Description PIN NME FUNCTION 1 eceiver Output. When is low and if ( - ) -5mV, is high; if ( - ) P -2mV, is low. 2 eceiver Output Enable. Drive low to enable ; is high impedance when is high. Drive high and low to enter low-power shutdown mode. is a hot-swap input (see the Hot-Swap Capability section for details). 3 Driver Output Enable. Drive high to enable driver outputs. These outputs are high impedance when is low. Drive high and low to enter low-power shutdown mode. is a hot-swap input (see the Hot-Swap Capability section for details). 4 Driver Input. With high, a low on forces noninverting output low and inverting output high. Similarly, a high on forces noninverting output high and inverting output low. 5 GND Ground 6 Noninverting eceiver Input and Noninverting Driver Output 7 Inverting eceiver Input and Inverting Driver Output 8 Positive Supply VCC = +5.V Q1%. ypass to GND with a.1ff capacitor. Function Tables TNSMITTING INPUTS OUTPUTS X X 1 1 X High-Z High-Z 1 X Shutdown CEIVING INPUTS OUTPUTS - X -5mV 1 X P -2mV X Open/shorted X High-Z 1 X Shutdown Maxim Integrated 9

10 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, Detailed Description The MX1478E high-speed transceiver for S-485/ S-422 communication contains one driver and one receiver. This device features fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see the Fail-Safe section). The MX1478E also features a hot-swap capability allowing line insertion without erroneous data transfer (see the Hot-Swap Capability section). The MX1478E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 5kbps. The MX1478E is a half-duplex transceiver and operates from a single +5.V supply. Drivers are output short-circuit current limited. Thermal-shutdown circuitry protects drivers against excessive power dissipation. When activated, the thermal-shutdown circuitry places the driver outputs into a high-impedance state. Fail-Safe The MX1478E guarantees a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver input threshold between -5mV and -2mV. If the differential receiver input voltage ( - ) is greater than or equal to -5mV, is logic-high. If ( - ) is less than or equal to -2mV, is logic-low. In the case of a terminated bus with all transmitters disabled, the receiver s differential input voltage is pulled to V by the termination. With the receiver threshold of the MX1478E, this results in a logic-high with a 5mV minimum noise margin. Unlike previous fail-safe devices, the -5mV to -2mV threshold complies with the ±2mV EI/TI- 485 standard. Hot-Swap Capability Hot-Swap Inputs When circuit boards are inserted into a hot or powered backplane, differential disturbances to the data bus can lead to data errors. Upon initial circuit board insertion, the data communication processor undergoes its own power-up sequence. During this period, the processor s logic-output drivers are high impedance and are unable to drive the and inputs of these devices to a defined logic level. Leakage currents up to ±1μ from the high-impedance state of the processor s logic drivers could cause standard CMOS enable inputs of a transceiver to drift to an incorrect logic level. dditionally, parasitic circuit board capacitance could cause coupling of VCC or GND to the enable inputs. Without the hot-swap capability, these factors could improperly enable the transceiver s driver or receiver. When VCC rises, an internal pulldown circuit holds low and high. fter the initial power-up sequence, the pulldown circuit becomes transparent, resetting the hot-swap tolerable input. Hot-Swap Input Circuitry The enable inputs feature hot-swap capability. t the input there are two nmos devices, M1 and M2 (Figure 9). When VCC ramps from zero, an internal 7μs timer turns on M2 and sets the S latch, which also turns on M1. Transistors M2, a 5μ current sink, and M1, a 1μ current sink, pull to GND through a 5kΩ resistor. M2 is designed to pull to the disabled state against an external parasitic capacitance up to 1pF that can drive high. fter 7μs, the timer deactivates M2 while M1 remains on, holding low against three-state leakages that can drive high. M1 remains on until an external source overcomes the required input current. t this time, the S latch resets and M1 turns off. When M1 turns off, reverts to a standard, high-impedance TIME TIME 5kΩ M1 1µ 5µ 1µs (HOT SWP) Figure 9. Simplified Structure of the Driver Enable Pin () M2 S LTCH 1 Maxim Integrated

11 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, CMOS input. Whenever VCC drops below 1V, the hotswap input is reset. For there is a complementary circuit employing two pmos devices pulling to VCC. ±3kV ESD Protection s with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver output and receiver input of the MX1478E have extra protection against static electricity. Maxim s engineers have developed state-of-the-art structures to protect these pins against ESD of ±3kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. fter an ESD event, the MX1478E keeps working without latchup or damage. ESD protection can be tested in various ways. The transmitter output and receiver input of the MX1478E are characterized for protection to the following limits: ±3kV using the Human ody Model ±12kV using the Contact Discharge method specified in IEC ±15kV using the ir-gap Discharge method specified in IEC ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results. Human ody Model Figure 1a shows the Human ody Model, and Figure 1b shows the current waveform it generates when discharged into a low impedance. This model consists of a 1pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5kΩ resistor. IEC The IEC standard covers ESD testing and performance of finished equipment. However, it does not specifically refer to integrated circuits. The MX1478E helps you design equipment to meet IEC , without the need for additional ESD-protection components. The major difference between tests done using the Human ody Model and IEC is higher peak current in IEC because series resistance is lower in the IEC model. Hence, the ESD withstand voltage measured to IEC is generally lower than that measured using the Human ody Model. Figure 1c shows the IEC model, and Figure 1d shows the current waveform for IEC ESD Contact Discharge test. Machine Model The machine model for ESD tests all pins using a 2pF storage capacitor and zero discharge resistance. The objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and assembly. Of course, all pins require this protection, not just S-485 inputs and outputs. C 1MΩ CHGE-CUNT- LIMIT SISTO D 15Ω SCHGE SISTNCE MPS I P 1% 9% I r PEK-TO-PEK INGING (NOT DWN TO SCLE) HIGH- VOLTGE DC SOUCE C s 1pF STOGE CPCITO VICE UN TEST 36.8% 1% t L TIME t DL CUNT WVEFOM Figure 1a. Human ody ESD Test Model Figure 1b. Human ody Current Waveform Maxim Integrated 11

12 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, C 5MΩ TO 1MΩ CHGE-CUNT- LIMIT SISTO D 33Ω SCHGE SISTNCE IPEK I 1% 9% HIGH- VOLTGE DC SOUCE C s 15pF STOGE CPCITO VICE UN TEST 1% t r =.7ns TO 1ns 3ns 6ns t Figure 1c. IEC ESD Test Model Figure 1d. IEC ESD Generator Current Waveform pplications Information The standard S-485 receiver input impedance is 12kΩ (1-unit load), and the standard driver can drive up to 32-unit loads. The MX1478E has a 1/8-unit load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one communication line. ny combination of the MX1478E, as well as other S-485 transceivers with a total of 32-unit loads or fewer, can be connected to the line. educed EMI and eflections The MX1478E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 5kbps. Low-Power Shutdown Mode Low-power shutdown mode is initiated by bringing both high and low. In shutdown, the devices typically draw only 2.8μ of supply current. and can be driven simultaneously; the devices are guaranteed not to enter shutdown if is high and is low for less than 5ns. If the inputs are in this state for at least 7ns, the devices are guaranteed to enter shutdown. Enable times tzh and tzl (see the Switching Characteristics section) assume the devices were not in a low-power shutdown state. Enable times tzh(shdn) and tzl(shdn) assume the devices were in shutdown state. It takes drivers and receivers longer to become enabled from low-power shutdown mode (tzh(shdn), tzl(shdn)) than from driver/receiver-disable mode (tzh, tzl). Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whole common-mode voltage range (see the Typical Operating Characteristics). The second, a thermal-shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature exceeds +175 C (typ). Line Length The S-485/S-422 standard covers line lengths up to 4ft. For line lengths greater than 4ft, it may be necessary to implement a line repeater. 12 Maxim Integrated

13 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, D 12Ω 12Ω D MX1478E D D Figure 11. Typical Half-Duplex S-485 Network Typical pplications The MX1478E transceiver is designed for bidirectional data communications on multipoint bus transmission lines. Figure 11 shows a typical network applications circuit. To minimize reflections, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MX1478E is more tolerant of imperfect termination. PCESS: icmos Chip Information Package Information For the latest package outline information and land patterns (footprints), go to Note that a +, #, or - in the package code indicates ohs status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of ohs status. PCKGE TYPE PCKGE CO OUTLINE NO. LND PTTEN NO. 8 SO S PP P Maxim Integrated 13

14 MX1478E +5.V, ±3kV ESD-Protected, Fail-Safe, VISION NUME VISION DTE SCIPTION evision History PGES CHNGED 12/1 Initial release 1 7/11 dded PP package information to data sheet 1, 2, 9, /11 Updated DC Electrical Characteristics including adding new row for Input Impedance on First Transition after PO Delay, updated Hot-Swap Input Circuitry section 3 1/15 Updated General Description and enefits and Features sections 1 2, 1 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 14 Maxim Integrated 16 io obles, San Jose, C US Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.