Complete, Isolated RS-485/RS-422 Data Interface MAX1480A/B/C/MAX1490A/B

Transcription

1 9-259; Rev 5; 5/5 Complete, Isolated RS-485/RS-422 General Description The MX48/MX48/MX48C/MX49/ MX49 are complete, electrically isolated, RS-485/ RS-422 data-communications interface solutions in a hybrid microcircuit. Transceivers, optocouplers, and a transformer provide a complete interface in a standard P package. single +5V supply on the logic side powers both sides of the interface. The MX48/MX48C/MX49 feature reducedslew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission at data rates up to 25kbps. The MX48/MX49 driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. The MX48//C are designed for half-duplex communication, while the MX49/ feature full-duplex communication. Drivers are short-circuit current limited and protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a highimpedance state. The receiver input has a fail-safe feature that guarantees a known output ( low for the MX48//C, high for the MX49/) if the input is open circuit. The MX48/MX48/MX48C/MX49/ MX49 typically withstand 6V RMS ( minute) or 2VRMS ( second). Their isolated outputs meet all RS-485/RS-422 specifications. The MX48//C are available in a 28-pin P package, and the MX49/ are available in a 24-pin P package. pplications Isolated RS-485/RS-422 Transceivers for EMI-Sensitive pplications Industrial-Control Local rea Networks utomatic Test Equipment HVC/uilding Control Networks Next-Generation Device Features For Integrated ESD Protection MX48E/MX49E: ±5kV ESD-Protected, Isolated RS-485/RS-422 s For Space-Constrained pplications MX357: High CMRR, RS-485 Transceiver with ±5V Isolation Ordering Information PRT TEMP RNGE PIN-PCKGE MX48CPI C to +7 C 28 Wide Plastic P MX48EPI -4 C to +85 C 28 Wide Plastic P Ordering Information continued at end of data sheet. Data rate for parts is up to 2.5Mbps. Data rate for and C parts is up to 25kbps. Selection Table PRT TOP VIEW HLF/ FULL DUPLEX V CC 24 C MX49/ V CC C2 D 3 22 ISO V CC D2 4 2 ISO DRV GND FS SD V CC Z Y MX845 DT RTE (MPS) MX488 MX49 SLEW- RTE LIMITED DRIVER ENLE TIME (µs) MX48 Half 2.5 No.2 MX48 Half.25 Yes 35 MX48C Half.25 Yes.5 MX49 Full 2.5 No MX49 Full.25 Yes Pin Configurations MX48//C/MX49/ 9 6 ISO COM V CC4 5 ISO DRV 4 ISO V CC2 GND2 2 3 ISO LED ISOLTION RRIER P Pin Configurations continued at end of data sheet. Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 MX48//C/MX49/ SOLUTE MXIMUM RTINGS With Respect to GND_ Supply Voltage (V CC_ )...-.3V to +6V Control Input Voltage (SD, FS)...-.3V to (V CC_ +.3V) Receiver Output Voltage (, )...-.3V to (V CC_ +.3V) Output Switch Voltage (D, D2)...+2V With Respect to ISO COM_ Control Input Voltage (ISO DE_ )...-.3V to (ISO V CC_ +.3V) Driver Input Voltage (ISO _ )...-.3V to (ISO V CC_ +.3V) Receiver Output Voltage (ISO _)...-.3V to (ISO V CC_ +.3V) Driver Output Voltage (,, Y, Z )...-8V to +2.5V Receiver Input Voltage (, )...-8V to +2.5V Stresses beyond those listed under bsolute Maximum Ratings 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. ELECTRICL CHRCTERISTICS LED Forward Current (, DE, ISO LED)...5m Continuous Power Dissipation (T = +7 C) 24-Pin Plastic P (derate 8.7mW C above +7 C)...696mW 28-Pin Plastic P (derate 9.9mW/ C above +7 C)..727mW Operating Temperature Ranges MX48_CPI/MX49_CPG... C to +7 C MX48_EPI/MX49_EPG...-4 C to +85 C Storage Temperature Range C to +6 C Lead Temperature (soldering, s)...+3 C (V CC_ = 5V ±%, V FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) (Notes, 2) Switch Frequency PRMETER SYMOL CONTIONS MIN TYP MX UNITS Operating Supply Current Shutdown Supply Current (Note 3) Shutdown Input Threshold f SWL V FS = V 535 f SWH FS = V CC_ or open 725 I CC MX48, R L =, +25 C only 6 9 DE = V CC_ or open R L = 54Ω 2 MX48, R L =, +25 C only DE = V CC_ or open R L = 54Ω 95 MX48C, R L =, +25 C only DE = V CC_ or open R L = 54Ω 95 MX49 MX49 R L =, +25 C only 5 R L = 54Ω 7 R L =, +25 C only R L = 54Ω 3 I SHDN SD = V CC_.2 µ V SDH High 2.4 V SDL Low.8 Shutdown Input Leakage Current p FS Input Threshold V FSH High 2.4 V FSL Low.8 FS Input Pullup Current FS low 5 µ FS Input Leakage Current FS high p Input High Voltage V IH DE, V CC_ -.4 V Input Low Voltage V IL DE,.4 V Isolation Resistance R ISO T = +25 C, V ISO = 5VDC, MΩ Isolation Capacitance C ISO T = +25 C, V ISO = 5VDC pf Differential Driver Output (No Load) V OD 8 V khz m V V 2

3 ELECTRICL CHRCTERISTICS (continued) (V CC_ = 5V ±%, V FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) (Notes, 2) PRMETER SYMOL CONTIONS MIN TYP MX UNITS Differential Driver Output (With Load) Change in Magnitude of Differential Output Voltage for Complementary Output States Driver Common-Mode Output Voltage Input Current (, ) ISO I IN V CC_ = V DE = V, V IN = 2V or 5.5V V IN = -7V Receiver Input Resistance R IN -7V V CM 2V Receiver Differential Threshold Voltage R = 5Ω (RS-422) 2 V OD2 R = 27Ω (RS-485), Figure R = 27Ω or 5Ω, Differential.3 ΔV OD Figure 4 Common mode.3 V OC R = 27Ω or 5Ω, Figure 4 4 V MX48//C MX49/.25 MX48//C.8 MX49/.2 MX48//C 48 MX49/ 2 V TH -7V V CM 2V V Receiver Input Hysteresis ΔV TH V CM = V 7 mv Receiver Output/Receiver Output Low Voltage Receiver Output/Receiver Output High Current V OL Using resistor values listed in Tables and 2 V V m kω.4 V I OH V OUT = 5.5V 25 µ Driver Short-Circuit Current ISO I OSD -7V V O 2V (Note 4) m MX48//C/MX49/ SWITCHING CHRCTERISTICS MX48/MX49 (V CC_ = 5V ±%, FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) PRMETER SYMOL CONTIONS MIN TYP MX UNITS Driver Input to Output t PLH Figures 5 and 7, R FF = 54Ω, C L = C L2 275 Propagation Delay t PHL = pf 275 ns Driver Output Skew t SKEW Figures 5 and 7, R FF = 54Ω, C L = C L2 = pf Driver Rise or Fall Time t R, t F Figures 5 and 7, R FF = 54Ω, C L = C L2 = pf 25 9 ns 5 4 ns Driver Enable to Output High (MX48 Only) Driver Enable to Output Low (MX48 Only) Driver Disable Time from Low (MX48 Only) t ZH Figures 6 and 8, C L = pf, S2 closed.2.5 µs t ZL Figures 6 and 8, C L = pf, S closed.2.5 µs t LZ Figures 6 and 8, C L = 5pF, S closed.2.5 µs Driver Disable Time from High (MX48 Only) t HZ Figures 6 and 8, C L = 5pF, S2 closed.2.5 µs Receiver Input to Output t PLH Figures 5 and, R FF = 54Ω, C L = C L2 225 Propagation Delay t PHL = pf 225 ns 3

4 MX48//C/MX49/ SWITCHING CHRCTERISTICS MX48/MX49 (continued) (V CC_ = 5V ±%, FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) PRMETER SYMOL CONTIONS MIN TYP MX UNITS t PLH - t PHL Differential Receiver Skew t SKD Figures 5 and, R FF = 54Ω, C L = C L2 = pf 2 ns Maximum Data Rate f MX t PLH, t PHL < 5% of data period 2.5 Mbps Time to Shutdown t SHDN µs Shutdown to Driver Output High t ZH(SHDN) Figures 6 and 9, C L = pf, S2 closed 3 µs Shutdown to Driver Output Low t ZL(SHDN) Figures 6 and 9, C L = pf, S closed 3 µs SWITCHING CHRCTERISTICS MX48/MX48C/MX49 (V CC_ = 5V ±%, FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) PRMETER SYMOL CONTIONS MIN TYP MX UNITS Driver Input to Output t PLH Figures 5 and 7, R FF = 54Ω, 2 3. Propagation Delay t PHL C L = C L2 = pf 2 3. Driver Output Skew t SKEW Figures 5 and 7, R FF = 54Ω, C L = C L2 = pf Driver Rise or Fall Time t R, t F Figures 5 and 7, R FF = 54Ω, C L = C L2 = pf µs 9 6 ns. 2. µs Driver Enable to Output High (MX48 Only) Driver Enable to Output Low (MX48 Only) Driver Disable Time from Low (MX48 Only) Driver Disable Time from High (MX48 Only) Driver Enable to Output High (MX48C Only) Driver Enable to Output Low (MX48C Only) t ZH Figures 6 and 8, C L = pf, S2 closed 35 µs t ZL Figures 6 and 8, C L = pf, S closed 35 µs t LZ Figures 6 and 8, C L = 5pF, S closed 3 5 µs t HZ Figures 6 and 8, C L = 5pF, S2 closed 3 5 µs t ZH Figures 6 and 8, C L = pf, S2 closed µs t ZL Figures 6 and 8, C L = pf, S closed µs 4

5 SWITCHING CHRCTERISTICS MX48/MX48C/MX49 (continued) (V CC_ = 5V ±%, FS = V CC_, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC_ = 5V and T = +25 C.) PRMETER SYMOL CONTIONS MIN TYP MX UNITS Driver Disable Time from Low (MX48C Only) Driver Disable Time from High (MX48C Only) t LZ Figures 6 and 8, C L = 5pF, S closed µs t HZ Figures 6 and 8, C L = 5pF, S2 closed µs Receiver Input to Output t PLH Figures 5 and, R FF = 54Ω, 2 3. Propagation Delay t PHL C L = C L2 = pf 2 3. t PLH - t PHL Differential Receiver Skew t SKD Figures 5 and, R FF = 54Ω, C L = C L2 = pf Note : ll currents into device pins are positive; all currents out of device pins are negative. ll voltages are referenced to logicside ground (GND_), unless otherwise specified. Note 2: For DE and pin descriptions, see Detailed lock Diagram and Typical pplication Circuit (Figure for MX48/ MX48/MX48C, Figure 2 for MX49/MX49). Note 3: Shutdown supply current is the current at V CC and V CC2 when shutdown is enabled. Note 4: pplies to peak current (see Typical Operating Characteristics). lthough the MX48//C and MX49/ provide electrical isolation between logic ground and signal paths, they do not provide isolation between external shields and the signal paths (see Isolated Common Connection section). µs 2 ns Maximum Data Rate f MX t PLH, t PHL < 5% of data period.25 Mbps Time to Shutdown t SHDN µs Shutdown to Driver Output High t ZH(SHDN) Figures 6 and 9, C L = pf, S2 closed 35 µs Shutdown to Driver Output Low t ZL(SHDN) Figures 6 and 9, C L = pf, S closed 35 µs MX48//C, MX49/ 5

6 MX48//C, MX49/ Typical Operating Characteristics (V CC_ = 5V, FS = V CC_, T = +25 C, unless otherwise noted.) OUTPUT CURRENT (m) OUTPUT LOW VOLTGE (V) OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTGE MESURED T ISO DRV OUTPUT LOW VOLTGE (V) RECEIVER OUTPUT LOW VOLTGE vs. TEMPERTURE MESURED T ISO DRV I = 8m TEMPERTURE ( C) MX48/9/- MX48/9/-4 OUTPUT CURRENT (m) OUTPUT CURRENT (m) OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTGE MESURED T ISO DRV OUTPUT HIGH VOLTGE (V) OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTGE OUTPUT LOW VOLTGE (V) MX48/9/-2 MX48/9/-5 OUTPUT HIGH VOLTGE (V) OUTPUT CURRENT (m) RECEIVER OUTPUT HIGH VOLTGE vs. TEMPERTURE MESURED T ISO DRV I = 8m TEMPERTURE ( C) OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTGE OUTPUT HIGH VOLTGE (V) MX48/9/-3 MX48/9/-6 OUTPUT CURRENT (m) DRIVER OUTPUT CURRENT vs. FFERENTIL OUTPUT VOLTGE = HIGH OR OPEN FFERENTIL OUTPUT VOLTGE (V) MX48/9/-7 FFERENTIL OUTPUT VOLTGE (V) DRIVER FFERENTIL OUTPUT VOLTGE vs. TEMPERTURE = HIGH OR OPEN R L = 54Ω TEMPERTURE ( C) MX48/9/-8 SHUTDOWN CURRENT (μ) MX48/MX48C/MX49 SHUTDOWN CURRENT vs. TEMPERTURE.4 SD = V CC_, = V CC_.35 DE (MX48/C ONLY) = V CC_ MESURED T V CC ND V CC TEMPERTURE ( C) MX48/9/-9 6

7 Typical Operating Characteristics (continued) (V CC_ = 5V, FS = V CC_, T = +25 C, unless otherwise noted.) SUPPLY CURRENT (m) MX48 SUPPLY CURRENT vs. TEMPERTURE DE = V CC V CC = 5.5V V CC = 5.V V CC = 4.5V V CC = 5.5V V CC = 5.V V CC = 4.5V R L = 54Ω R L = TEMPERTURE ( C) SUPPLY CURRENT (m) MX48/9/- SUPPLY CURRENT (m) 4 2 MX49 SUPPLY CURRENT vs. TEMPERTURE V CC = 5.V V CC = 5.5V V CC = 5.V V CC = 4.5V V CC = 5.5V R L = 54Ω R L = V CC = 4.5V TEMPERTURE ( C) MX48 SUPPLY CURRENT vs. TEMPERTURE DE = V CC V CC = 5.5V V CC = 5.5V V CC = 5.V V CC = 4.5V V CC = 5.V R L = 54Ω R L = V CC = 4.5V TEMPERTURE ( C) MX48/9/-3 SUPPLY CURRENT (m) MX48/9/- SUPPLY CURRENT (m) MX48C SUPPLY CURRENT vs. TEMPERTURE DE = V CC V CC = 5.5V V CC = 5.V V CC = 4.5V V CC = 5.V V CC = 5.5V R L = 54Ω R L = 3 V CC = 4.5V TEMPERTURE ( C) MX49 SUPPLY CURRENT vs. TEMPERTURE V CC = 5.V V CC = 5.5V V CC = 5.V V CC = 4.5V V CC = 5.5V R L = 54Ω R L = 6 V CC = 4.5V TEMPERTURE ( C) MX48/9/-4 MX48/9/-2 MX48//C, MX49/ DRIVER SLE TIME (μs) DRIVER SLE TIME vs. TEMPERTURE MX48 MX48C RL = 54Ω V = V MESURED FM DE TO VLID OUTPUT MX48/9/-5a DRIVER ENLE TIME (μs) DRIVER ENLE TIME vs. TEMPERTURE MX48 RL = 54Ω V = V MESURED FM DE TO VLID OUTPUT MX48C MX48/9/-5b MX TEMPERTURE ( C) MX TEMPERTURE ( C) 7

8 MX48//C, MX49/ Typical Operating Characteristics (continued) (V CC_ = 5V, FS = V CC_, V = V, DE toggled V to 5V at 5kHz, T = +25 C, unless otherwise noted.) MX48 DRIVER ENLE TIME 2ns/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kHz MX48 DRIVER ENLE TIME MX48/9-9 MX48/9-7 DRIVER OUTPUT DE DRIVER OUTPUT MX48 DRIVER SLE TIME 2ns/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kHz MX48 DRIVER SLE TIME MX48/9-2 MX48/9-8 DRIVER OUTPUT DE DRIVER OUTPUT DE DE μs/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kHz MX48C DRIVER ENLE TIME 5μs/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kHz MX48C DRIVER SLE TIME MX48/9-25 DRIVER OUTPUT MX48/9-26 DRIVER OUTPUT DE DE 5ns/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kH 5ns/div V CC_ = 5.V, = V DE TOGGLED V TO 5V T 5kHz 8

9 Typical Operating Characteristics (continued) (V CC_ = 5V, FS = V CC_, DE = V CC_, V = V to 5V at.25mhz, T = +25 C, unless otherwise noted.) V CC_ = 5.V, DE = V CC_ = V TO 5V T.25MHz MX48/MX49 RECEIVER t PHL 2ns/div MX48/MX48C/MX49 RECEIVER t PHL MX48/9-2 MX48/9-23 RECEIVER INPUT V/div RECEIVER INPUT V/div / RECEIVER INPUT V/div RECEIVER INPUT V/div V CC_ = 5.V, DE = V CC_ = V TO 5V T.25MHz MX48/MX49 RECEIVER t PLH 2ns/div MX48/MX48C/MX49 RECEIVER t PLH MX48/9-22 MX48/9-24 RECEIVER INPUT V/div RECEIVER INPUT V/div / RECEIVER INPUT V/div RECEIVER INPUT V/div MX48//C, MX49/ / / V CC_ = 5.V, DE = V CC_ = V TO 5V T 25kHz 2ns/div V CC_ = 5.V, DE = V CC_ = V TO 5V T 25kHz POWER-UP DELY TO DRIVER OUTPUTS VLID 5ns/div MX48/9-6 DRIVER OUTPUT (Z FOR MX49) SD V = V V SD = 5V TO V T khz μs/div 9

10 MX48//C, MX49/ Pin Description MX48//C, 2, 8, 3, PIN MX49/ PINS ON THE NON-ISOLTED SIDE, 2, 8, 3, NME V CC V CC4 D, D2 GND FS SD DE GND2 4 V CC5 PINS ON THE ISOLTED RS-485/RS-422 SIDE FUNCTION Logic-Side (nonisolated side) +5V Supply Voltages Internal Connections. Leave these pins unconnected. Logic-Side Ground. Connect to GND2 (pin 2). Frequency Select Input. If FS = V CC_ or is open, switch frequency is high; if FS = GND, switch frequency is low. For optimal performance and minimal supply current, connect FS to V CC_ or leave unconnected. Shutdown Input. Ground for normal operation. When high, the power oscillator is disabled. Driver Input. With DE high (MX48//C only), a low on forces output low and output high. Similarly, a high on forces output high and output low. Drives internal LED cathode through a resistor (Table of Figure for MX48//C, Table 2 of Figure 2 for MX49/). Driver-Enable Input. The driver outputs, and, are enabled by bringing DE high. The driver outputs are high impedance when DE is low. If the driver outputs are enabled, the device functions as a line driver. While the driver outputs are high impedance, the device functions as a line receiver. Drives internal LED cathode through a resistor (Table of Figure ). Receiver Output. If > by 2mV, will be high; if < by 2mV, will be low. Open collector; must have pullup to V CC (Table 2 of Figure 2). Logic-Side Ground. Connect to GND (pin 5). Receiver Output. If > by 2mV, will be low; if < by 2mV, will be high. Open collector; must have pullup to V CC_ (Table of Figure ). Logic-Side (non-isolated side) +5V Supply Voltage 5 3 ISO LED Isolated Receiver Output LED. Internal LED anode in MX48//C and LED cathode in MX49/. Connect to ISO DRV through a resistor (Table of Figure for MX48//C; Table 2 of Figure 2 for MX49/) ISO COM2 ISO DE DRV ISO V CC2 ISO DRV 2 6 ISO COM Isolated Common. Connect to ISO COM (pin 2). Isolated Driver-Enable Drive. The driver outputs, and, are enabled by bringing DE high. The driver outputs are high impedance when DE is low. If the driver outputs are enabled, the device functions as a line driver. While the driver outputs are high impedance, the device functions as a line receiver. Opencollector output; must have pullup to ISO V CC_ and be connected to ISO DE IN for normal operation (Table of Figure ). Isolated Supply Voltage. Connect to ISO V CC (pin 26 for MX48//C, or pin 22 for MX49/). Isolated Driver-Input Drive. With DE high (MX48//C only), a low on forces output low and output high. Similarly, a high on forces output high and output low. Connect to ISO IN (on the MX48//C only) for normal operation. Open-collector output; connect a pullup resistor to ISO V CC_ (Table of Figure for MX48//C; Table 2 of Figure 2 for MX49/). Isolated Common. For MX48//C, connect to ISO COM2 (pin 6) (Figures and 2).

11 Pin Description (continued) MX48//C PIN MX49/ 8 Z Inverting Driver Output 9 Inverting Receiver Input 2 Noninverting Receiver Input 2 ISO DE IN Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation. 22 ISO IN Isolated Driver Input. Connect to ISO DRV for normal operation. 23 Noninverting Driver Output and Noninverting Receiver Input 24 2 NME PINS ON THE ISOLTED RS-485/RS-422 SIDE (continued) 7 Y Noninverting Driver Output ISO DRV 25 Inverting Driver Output and Inverting Receiver Input ISO V CC Isolated Supply Voltage Source 27, 28 23, 24 C2, C Internal Connections. Leave these pins unconnected. Note: For DE and pin descriptions, see Detailed lock Diagram and Typical pplication Circuit (Figure for MX48//C, Figure 2 for MX49/). Detailed Description The MX48/MX48/MX48C/MX49/ MX49 are complete, electrically isolated, RS-485/ RS-422 data-communications interface solutions. Transceivers, optocouplers, a power driver, and a transformer in one standard 28-pin P package (24- pin for the MX49/) provide a complete interface. Signals and power are internally transported across the isolation barrier (Figures, 2). Power is transferred from the logic side (nonisolated side) to the isolated side of the barrier through a center-tapped transformer. Signals cross the barrier through high-speed optocouplers. single +5V supply on the logic side powers both sides of the interface. The MX48//C offer half-duplex communications while the MX49/ feature full-duplex communication. The functional input/output relationships are shown in Tables 3 6. The MX48/MX48C/MX49 feature reducedslew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission at data rates up to 25kbps. The MX48/MX49 driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. The MX48/MX48C/MX49 shutdown feature reduces supply current to as low as.2µ by using the SD pin (see the Low-Power Shutdown Mode section). FUNCTION Isolated Receiver-Output Drive. Connect to ISO LED through a resistor (Table of Figure for MX48//C, Table 2 of Figure 2 for MX49/). Use the FS pin to select between high and low switching frequencies for the isolated power driver. The driver switches at the lower frequency 535kHz when FS is low, and at the higher frequency 725kHz when FS is high. The FS pin has a weak internal pull-up that switches the device to the high-frequency mode when FS is left unconnected. With FS high or open, no-load supply current is reduced by approximately 4m, and by up to 8m when fully loaded. For optimal performance and minimal supply current, connect FS to V CC_ or leave unconnected. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that puts the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high (logic-low ) output if the input is open circuit. On the MX48//C, the driver outputs are enabled by bringing DE high. Driver-enable times are typically.2µs for the MX48, 35µs for the MX48, and.5µs for the MX48C. llow time for the devices to be enabled before sending data (see the Driver Enable Time vs. Temperature graph in the Typical Operating Characteristics). When enabled, driver outputs function as line drivers. Driver outputs are high impedance when DE is low. While outputs are high impedance, they function as line receivers. MX48//C, MX49/

12 MX48//C, MX49/ FS DE OSC.7MHz/.45MHz V IN 5V 74HC86 OR EQUIVLENT V CC3 C T 22μF F/F Q Q DRIVER INPUT DRIVER ENLE RECEIVER OUTPUT SD C2.μF DE R R2 R3 MX845 N N GND V CC V CC2 2 D 3 D2 4 GND 5 FS 6 SD 7 V CC3 8 9 V CC4 DE GND2 2 3 V CC5 4 D D2 MX48//C MX845 MX487 MX487 ISO DRV 28 C (MKE NO CONNECTION) 27 C2 (MKE NO CONNECTION) ISO IN ISO DE IN ISO V CC ISO DRV ISO IN ISO DE IN ISO COM ISO DRV ISO V CC2 ISO DE DRV ISO COM2 ISO LED D ISO V CC RE ISO COM R6 R MX48: MX487 MX48: MX487 MX48C: MX487 R4 R5 EXTERNL RS-485/RS-422 WIRING SH R7 Ω TERMINTING RESISTOR (ONE RESISTOR ON ECH END) TWISTED PIR TO OTHER TRNSCEIVERS SHIELD (OPTIONL) TWISTED PIR TO OTHER TRNSCEIVERS SHIELD (OPTIONL) NOTE: RESISTOR R7 PTECTS THE MX48//C FM TRNSIENT CURRENTS ETWEEN SHIELD ND TRNSMISSION LINES. R L R L LOGIC GUND ISOLTION RRIER ISOLTED COMMON Table. Pull-Up and LED Drive Resistors PRT MX48 MX48 MX48C R (Ω) R2 (Ω) R3 (Ω) R4 (Ω) R5 (Ω) R6 (Ω) Figure. MX48/MX48/MX48C Detailed lock Diagram and Typical pplication Circuit The MX48/MX48/MX48C/MX49/ MX49 typically withstand 6VRMS ( minute) or 2V RMS ( second). The logic inputs can be driven from TTL/CMOS-logic with a series resistor, and the received data output can directly drive TTL or CMOSlogic families with only resistive pullup. Low-Power Shutdown Mode The SD pin shuts down the oscillator on the internal power driver. With the primary side in shutdown, no power is transferred across the isolation barrier. The and DE optocouplers, however, still consume current if the drive signals on the nonisolated side are low. Therefore, leave and DE high or floating when in shutdown mode. 2

13 FS V IN 5V OSC.7MHz/.45MHz C 22μF 74HC86 OR EQUIVLENT V CC3 DRIVER INPUT T C2.μF F/F RECEIVER OUTPUT Q Q R R2 SD MX845 V CC V CC2 2 D 3 D2 4 GND 5 FS 6 SD 7 V CC3 8 9 V CC4 R GND2 2 N N GND MX49/ MX845 MX488 MX49 ISOLTION RRIER D D2 ISO DRV ISO DRV 24 C (MKE NO CONNECTION) 23 C2 (MKE NO CONNECTION) 22 ISO V CC 2 ISO DRV Z 7 Y 6 ISO COM 5 ISO DRV 4 ISO V CC2 3 ISO LED R3 MX49: MX49 MX49: MX488 D R4 R Z Y R5, Ω SH R6, Ω ISOLTED COMMON SH2 Z Y EXTERNL RS-485/RS-422 WIRING R L R L TERMINTING RESISTOR (ONE RESISTOR ON ECH END) TWISTED PIR TO OTHER TRNSCEIVERS SHIELD (OPTIONL) TWISTED PIR TO OTHER TRNSCEIVERS SHIELD (OPTIONL) NOTE: RESISTORS R5 ND R6 PTECT THE MX49/ FM TRNSIENT CURRENTS ETWEEN SHIELD ND TRNSMISSION LINES. R L R L MX48//C, MX49/ LOGIC GUND Table 2. Pull-Up and LED Drive Resistors PRT R (Ω) R2 (Ω) R3 (Ω) R4 (Ω) MX MX Figure 2. MX49/MX49 Detailed lock Diagram and Typical pplication Circuit Under these conditions, the MX48/MX48C/ MX49 supply current is reduced to as low as.2µ. The high-speed optocouplers on the MX48/ MX48C/MX49 consume an additional m through VCC5 (VCC4 for the MX49). Therefore, to completely shut down these devices, use an external P- channel MOSFET as shown in Figure 3. In normal operation, SD is low, turning the MOSFET on and thereby providing power to all the V CC_ pins. When SD is pulled high, the power oscillator is disabled and the switch is turned off, disconnecting power from the and DE optocouplers. In normal operating mode, the switch carries only the optocoupler currents, so an on-resistance of several ohms will not significantly degrade efficiency. 3

14 MX48//C, MX49/ V IN 5V SHUTDOWN DE Si94334 R R2 P R3 V CC V CC2 2 D 3 D2 4 GND 5 FS 6 SD 7 V CC3 8 9 V CC4 DE GND2 2 3 V CC5 4 GND MX845 MX487 ISOLTION RRIER MX48 C C2 ISO V CC ISO DRV ISO IN ISO DE IN ISO COM ISO DRV ISO V CC2 ISO DE DRV ISO COM2 ISO LED Figure 3. MX48 Low-Power Shutdown Mode Test Circuits R ISOLTION RRIER (DE ) ISOLTION RRIER D V OD C L ( ) RE FOR THE MX48//C R V OC D V ID R FF R ()* C L2 * OPTOCOUPLER OUTPUTS. SEE FIGURES ND 2 FOR DETILED LOCK GRM ND TYPICL PPLICTION CIRCUIT. Figure 4. Driver DC Test Load Figure 5. Driver/Receiver Timing Test Circuit 4

15 Test Circuits (continued) V CC_ -.4V V FF V V O V -V O V CC_ -.4V 2 V O /2 V O t R % t PLH V FF = V () - V () 9% 9% OUTPUT UNDER TEST C L 5Ω Figure 6. Driver Timing Test Load t PHL t F t SKEW = t PLH - t PHL V CC_ -.4V 2 /2 VO %, V OL, V S S2 V CC_ -.4V V CC_ -.4V DE V 2 ISO V CC _ Switching Waveforms 2.3V OUTPUT NORMLLY LOW 2.3V t ZL t ZH t LZ OUTPUT NORMLLY HIGH t HZ V CC_ -.4V 2 V OL +.5V V OH -.5V MX48//C, MX49/ Figure 7. Driver Propagation Delays and Transition Times Figure 8. Driver Enable and Disable Times 2.4V SD.8V.6V.6V V - V V ID -V ID V INPUT V, V OL, V t ZL(SHDN) t SHDN 2.3V OUTPUT NORMLLY LOW OUTPUT NORMLLY HIGH 2.3V t ZH(SHDN) t SHDN V OL +.5V V OH -.5V V OH V OL V OH V OL.5V.5V t PLH.5V t PHL MX49/ OUTPUT MX48//C OUTPUT.5V t SKEW = t PLH - t PHL t PHL t PLH Figure 9. Times to/from Shutdown Figure. Receiver Propagation Delays 5

16 MX48//C, MX49/ MX48/MX48C/MX49: Reduced EMI and Reflections The MX48/MX48C/MX49 are slew-ratelimited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure shows both the driver output waveform of a MX48/MX49 transmitting a 5kHz signal and the Fourier analysis of that waveform. High-frequency harmonics with large amplitudes are evident. Figure 2 shows the same information for the slew-ratelimited MX48/MX48C/MX49 transmitting the same signal. The high-frequency harmonics have much lower amplitudes, and therefore the potential for EMI is significantly reduced. d/div Function Tables Table 3. Transmitting DE Half-Duplex Devices (MX48/MX48/MX48C) INPUTS* X X = Don t care High-Z = High impedance Table 4. Receiving DE INPUTS* OUTPUTS High-Z High-Z OUTPUT V - V () +.2V -.2V Open Hz 5kHz/div Figure. Driver Output Waveform and FFT Plot of MX48/MX49 Transmitting a 5kHz Signal d/div 5MHz Table 5. Transmitting INPUT* ( ) Table 6. Receiving Full-Duplex Devices (MX49/MX49) Z OUTPUTS Y * For DE and pin descriptions, see Detailed lock Diagram and Typical pplication Circuit (Figure for MX48//C, Figure 2 for MX49/). Hz 5kHz/div 5MHz Figure 2. Driver Output Waveform and FFT Plot of MX48/MX48C/MX49 Transmitting a 5kHz Signal INPUT (V - V ) +.2V -.2V Open OUTPUT () 6

17 RE V IN 5V R DE D RE V CC R DE TERMINTING RESISTOR (ONE RESISTOR ON ECH END) D MX48//C 2Ω Ω TERMINTING RESISTOR (ONE RESISTOR ON ECH END) 28 C (MKE NO CONNECTION) R RE D DE MX48//C, MX49/ C C2 V CC C2 (MKE NO CONNECTION) DE 22μF 74HC86 OR EQUIVLENT.μF DRIVER INPUT DRIVER ENLE RECEIVER OUTPUT R R2 R3 D D2 GND FS SD V CC3 V CC4 DE GND2 V CC MX845 MX487 MX ISO V CC ISO DRV ISO IN ISO DE IN ISO COM ISO DRV ISO V CC2 ISO DE DRV ISO COM2 ISO LED R6 R4 R5 2Ω SH SHIELD (OPTIONL) NOTE: RESISTOR R7 PTECTS THE MX48//C FM TRNSIENT CURRENTS ETWEEN SHIELD ND R7 Ω TRNSMISSION LINES. LOGIC GUND ISOLTION RRIER ISOLTED COMMON Figure 3. Typical Half-Duplex RS-485/RS-422 Network 7

18 MX48//C, MX49/ Driver Output Protection There are two mechanisms to prevent excessive output current and power dissipation caused by faults or by bus contention. foldback current limit on the output stage provides immediate protection against short circuits over the entire common-mode range (see the Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature rises excessively. Propagation Delay Skew Typical propagation delays are shown in the Typical Operating Characteristics using the test circuit of Figure 5. Propagation delay skew is simply the difference between the low-to-high and high-to-low propagation delay. Small driver/receiver skew times help reduce EMI and reflections by maintaining balanced differential signals. The receiver skew time, I tplh - tphl I, is typically under ns for the MX48/MX49 and under µs for the MX48/MX48C/MX49. The driver skew time is typically 25ns for the MX48/MX49 and ns for the MX48/ MX48C/MX49. pplications Information and DE are intended to be driven through a series current-limiting resistor. Directly grounding these pins destroys the device. The MX48/MX48/MX48C are designed for bidirectional data communications on multipoint bus-transmission lines. The MX49/MX49 are designed for full-duplex bidirectional communications that are primarily point-to-point. Figures 3 and 4 show half-duplex and full-duplex typical network application circuits, respectively. To minimize reflections, terminate the line at both ends with its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MX48/ MX48C/MX49 are more tolerant of imperfect termination and stubs off the main line. Layout Considerations The MX48/MX48/MX48C/MX49/ MX49 pinouts enable optimal PC board layout by minimizing interconnect lengths and crossovers. For maximum isolation, the isolation barrier should not be breached except by the MX48/ MX48/MX48C/MX49/MX49. V IN 5V MX49/ C C2 V CC 24 C (MKE NO CONNECTION) 74HC86 OR EQUIVLENT 22μF DRIVER INPUT.μF R R2 RECEIVER OUTPUT V CC2 D D2 GND FS SD V CC3 V CC4 GND MX845 MX488 MX49 ISOLTION RRIER C2 (MKE NO CONNECTION) ISO V CC ISO DRV Z Y ISO COM ISO DRV ISO V CC2 ISO LED R3 R4 ISOLTED COMMON Z Y R5, Ω SH SH2 R6, Ω 2Ω 2Ω SHIELD (OPTIONL) SHIELD (OPTIONL) NOTE: RESISTORS R5 ND R6 PTECT THE MX49/ FM TRNSIENT CURRENTS ETWEEN SHIELD ND TRNSMISSION LINES. Y 2Ω Z 2Ω D R LOGIC GUND Figure 4. Typical Full-Duplex RS-485/RS-422 Network 8

19 Connections and components from one side should not be located near those of the other side. shield trace connected to the ground on each side of the barrier can help intercept capacitive currents that might otherwise couple into the signal path. In a double-sided or multilayer board, these shield traces should be present on all conductor layers. Try to maximize the width of the isolation barrier wherever possible; a clear space of at least.25 inches between ground and isolated common is suggested. Pullup and LED Drive Resistors The MX48/MX48/MX48C/MX49/ MX49 are specified and characterized using the resistor values shown in Table of Figure and Table 2 of Figure 2. ltering the recommended values can degrade performance. NETWORK SEGMENT +5V +5V The and DE (MX48//C only) inputs are the cathodes of LEDs whose anodes are connected to the supply. These points are best driven by a CMOS-logic gate with a series resistor to limit the current. The resistor values shown in Tables and 2 are recommended when the 74HC86 gate or equivalent is used. These values may need to be adjusted if a driving gate with dissimilar series resistance is used. ll pull-up resistors are based on optocoupler specifications in order to optimize the devices data-transfer rates. Isolated Common Connection The isolated common may be completely floating with respect to the logic ground and the effective network ground. The receiver input resistors will cause the isolated common voltage to go to the mean voltage of the receiver inputs. If using shielded cable, connect the isolated common to the shield through a Ω resistor. In the case of the MX49, each shield should have its own Ω resistor (Figures, 2, 3, and 4) kΩ Ω NETWORK SEGMENT MX48//C, MX49/ 3kΩ 2Ω 26 3kΩ 26 74HC4 3kΩ MX48C 9 2Ω MX48C 3kΩ DRIVER DRIVER ENLE ENLE 2 2Ω > > 2Ω Ω 3kΩ +5V 5kΩ pf Q 3 +5V 5kΩ pf 7 6 Q 5 74HC23 74HC23 Q 4 9 Q CLR CLR 3 2 Figure 5. Doubly Isolated RS-485 Repeater 9

20 MX48//C, MX49/ Doubly Isolated RS-485 Repeater The RS-422/RS-485 standard is specified for cable lengths up to 4 feet. When approaching or exceeding the specified maximum cable length, a groundpotential difference of several tens of volts can easily develop. This difference can be either DC, C, at power-line frequency, or any imaginable noise or impulse waveform. It is typically very low impedance so that if a connection between the two grounds is attempted, very large currents may flow. These currents are by their nature unstable and unpredictable. In addition, they may cause noise to be injected into sensitive instrumentation and, in severe cases, might actually cause physical damage to such equipment. Figure 5 shows a half-duplex (two-wire), bidirectional, party-line repeater system that prevents interference and/or damage from ground-potential differences. Two MX48/MX48/MX48C isolated RS-485 transceivers are used to isolate each of the network segments from the electrical environment of the repeater. The MX48/MX48/MX48C also regenerate bus signals that may have been degraded by line attenuation or dispersion. In the idle state, both transmitters are disabled, while all receivers in the system are enabled. If any device on the system has information for any other device, it starts sending its data onto the bus. Each data transmission on the bus retriggers the one-shot, keeping the sending transmitter enabled until there are no more transmissions. ll receivers receive all data; if this is undesirable, the protocol must allow for an address field so receivers can ignore data not directed to them. Each node must refrain from transmitting when data already exists on the bus, and must resend data that is corrupted by the collisions that inevitably occur with a party-line system. With the repeater of Figure 5, there might be transmitters up to 8 feet apart. That represents more than 8µs (assuming ns/foot of delay) in which two nodes could be transmitting simultaneously. The circuit in Figure 5 can be used either directly as shown, with the slew-rate-limited MX48/MX48C, for data transfer rates up to 25kbps, or with the MX48 for data rates up to 2.5Mbps (see Table for pullup and LED resistor values when using the MX48, MX48, or MX48C). If dual-port isolation is not needed, one of the MX48C devices can be replaced by a MX487 for 25kbps applications. 2

21 TOP VIEW Pin Configurations (continued) V CC V CC2 D D2 GND FS SD V CC V CC4 DE GND2 2 3 V CC5 4 MX845 MX487 MX487 ISOLTION RRIER P MX48//C 28 C 27 C2 26 ISO V CC ISO DRV ISO IN ISO DE IN 2 ISO COM 9 ISO DRV 8 ISO V CC2 7 ISO DE DRV 6 ISO COM2 5 ISO LED Ordering Information (continued) PRT TEMP RNGE PIN-PCKGE MX48CPI C to +7 C 28 Wide Plastic P MX48EPI -4 C to +85 C 28 Wide Plastic P MX48CCPI C to +7 C 28 Wide Plastic P MX48CEPI -4 C to +85 C 28 Wide Plastic P MX49CPG C to +7 C 24 Wide Plastic P MX49EPG -4 C to +85 C 24 Wide Plastic P MX49CPG C to +7 C 24 Wide Plastic P MX49EPG -4 C to +85 C 24 Wide Plastic P Data rate for parts is up to 2.5Mbps. Data rate for and C parts is up to 25kbps. Package Information For the latest package outline information and land patterns, go to Note that a +, #, or - in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PCKGE TYPE PCKGE CODE DOCUMENT NO. 28 PP P28M MX48//C, MX49/ Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 2 San Gabriel Drive, Sunnyvale, C Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.