19-1941; Rev 1; 3/6 ±15kV ES-Protected, Isolated, 3.3V General escription The MX348E/MX348E are electrically isolated RS-485/RS-4 data-communications interfaces. The RS-485/RS-4 I/O pins are protected against ±15kV electrostatic discharge (ES) shocks, without latchup. Transceivers, optocouplers, and a transformer are all included in one low-cost, 8-pin PIP package. single +3.3V supply on the logic side powers both sides of the interface. The MX348E features reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission at data rates up to 16kbps. The MX348E s driver slew rate is not limited, allowing transmission rates up to.5mbps. rivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The MX348E/MX348E are guaranteed to withstand 16VRMS (1min) or 15VRMS (1s). Their isolated inputs and outputs meet RS-485/RS-4 specifications. Features Isolated ata Interface Guaranteed to 16V RMS (1min) ±15kV ES Protection for I/O Pins Slew-Rate-Limited ata Transmission (16kbps for MX348E) High-Speed, Isolated,.5Mbps RS-485 Interface (MX348E) Single +3.3V Supply Current Limiting and Thermal Shutdown for river Overload Protection Standard 8-Pin PIP Package llows Up to 18 Transceivers on the us Pin Configuration MX348E/MX348E pplications Isolated RS-485/RS-4 ata Interface Transceivers for EMI-Sensitive pplications Industrial-Control Local rea Networks utomatic Test Equipment HVC/uilding Control Networks Telecom Ordering Information TOP VIEW V CC1 V CC 1 GN1 FS S 1 3 4 5 6 7 MX845 MX1487E MX487E 8 7 6 5 4 3 MX348E MX348E C1 C ISO V CC1 ISO RV ISO I IN PRT TEMP RNGE PI N - P C K G E* T R T E ( k b p s ) PKG COE MX348ECPI C to + 7 C 8 PIP 5 P8M-1 MX348EEPI - 4 C to + 85 C 8 PIP 5 P8M-1 MX348ECPI C to + 7 C 8 PIP 5 P8M-1 MX348EEPI - 4 C to + 85 C 8 PIP 5 P8M-1 *See the Reliability section at end of data sheet. V CC3 I V CC4 E GN V CC5 8 9 1 11 1 13 14 1 19 18 17 16 15 ISO E IN ISO COM1 ISO I RV ISO V CC ISO E RV ISO COM ISO LE ISOLTION RRIER PIP Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/allas irect! at 1-888-69-464, or visit Maxim s website at www.maxim-ic.com.
MX348E/MX348E SOLUTE MXIMUM RTINGS With Respect to GN Supply Voltage (V CC1, V CC, V CC4, V CC5 )...-.3V to +3.8V Supply Voltage (V CC3 )...-.3V to +7V Control Input Voltage (S, FS)...-.3V to (V CC3 +.3V) Receiver Output Voltage ()...-.3V to (V CC5 +.3V) With Respect to ISO COM Control Input Voltage (ISO E _)...-.3V to (ISO V CC_ +.3V) river Input Voltage (ISO I _)...-.3V to (ISO V CC_ +.3V) Receiver Output Voltage (ISO _)..-.3V to (ISO V CC_ +.3V) river Output Voltage (, )...-8V to +1.5V Receiver Input Voltage (, )...-8V to +1.5V 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 LE Forward Current (I, E, ISO LE)...5m Continuous Power issipation (T = +7 C) 8-Pin PIP (derate 9.9mW/ C above +7 C)...77mW Operating Temperature Ranges MX348E_CPI... C to +7 C MX348E_EPI...-4 C to +85 C Storage Temperature Range...-65 C to +15 C Lead Temperature (soldering, 1s)...+3 C (V CC = V CC1 = V CC = V CC4 = V CC5 = +3.V to +3.6V, FS =, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC = +3.3V and T = +5 C.) (Notes 1, ) Switch Frequency PRMETER SYMOL CONITIONS MIN TYP MX UNITS f SWL FS = 6 f SWH FS = V CC or open 9 MX348E, R L = 13 5 E = V CC or open R L = 54Ω Operating Supply Current I CC MX348E, R L = 8 E = V CC or open R L = 54Ω 18 Shutdown Supply Current (Note 3) I SHN S = V CC3. µ FS Input Threshold V FSH High.4 V FSL Low.8 FS Input Pullup Current I FSL FS low 5 µ FS Input Leakage Current I FSM FS high 1 p Input High Voltage V IH E, I, Figure 1 V CC -.4 V Input Low Voltage V IL E, I, Figure 1.4 V Isolation Voltage V ISO T = +5 C, 1min (Note 4) 16 V RMS Shutdown Input Threshold V SH High.4 1 V SL Low 1.8 Isolation Resistance R ISO T = +5 C, V ISO = ±5VC 1 1, MΩ Isolation Capacitance C ISO f = 1MHz 1 pf ES Protection ifferential river Output (No Load) ES,, Y, and Z pins, tested at Human ody Model khz m V V ±15 kv V O1 8 V R = 5Ω (RS-4) ifferential river Output V O R = 7Ω (RS-485), Figure 3 1.5 5. V Change in Magnitude of river Output Voltage for Complementary Output States V O R = 7Ω or 5Ω, Figure 3 ifferential.3 Common mode.3 V
ELECTRICL CHRCTERISTICS (continued) (V CC = V CC1 = V CC = V CC4 = V CC5 = +3.V to +3.6V, FS =, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC = +3.3V and T = +5 C.) (Notes 1, ) PRMETER SYMOL CONITIONS MIN TYP MX UNITS river Common-Mode Output V OC R = 7Ω or 5Ω, Figure 4 4 V Input Current (, ) ISO I IN V CC = or E =, +3.6V SWITCHING CHRCTERISTICS MX348E MX348E MX348E V IN = +1V.5 V IN = -7V -. V IN = +1V.5 V IN = -7V -. Receiver Input Resistance R IN -7V V CM 1V 48 kω Receiver ifferential Threshold V TH -7V V CM 1V -. +. V Receiver Input Hysteresis V TH V CM = 7 mv Receiver Output Low Voltage V OL I = V CC.4 V Receiver Output High Current I OH V OUT = +3.6V, I = 5 µ river Short-Circuit Current ISO I OS -7V V O 1V (Note 5) 1 m (V CC = V CC1 = V CC = V CC4 =V CC5 = +3.V to +3.6V, FS =, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC = +3.3V and T = +5 C.) m MX348E/MX348E PRMETER SYMOL CONITIONS MIN TYP MX UNITS river Input to Output t PLH Figures 4, 6; R IFF = 54Ω, 1 75 ns Propagation elay t PHL C L1 = C L = 1pF 1 75 river Output Skew t Figures 4, 6; R IFF = 54Ω, SKEW 5 1 ns C L1 = C L = 1pF (Note 5) river Rise or Fall Time t R, t Figures 4, 6; R IFF = 54Ω, F 15 5 ns C L1 = C L = 1pF river Enable to Output High t ZH Figures 5, 7; C L = 1pF, S closed.5 1.8 µs river Enable to Output Low t ZL Figures 5, 7; C L = 1pF, S1 closed.5 1.8 µs river isable Time from High t HZ Figures 5, 7; C L = 15pF, S closed.6 1.8 µs river isable Time from Low t LZ Figures 5, 7; CL = 15pF, S1 closed.6 1.8 µs Receiver Input to Output t PLH Figures 4, 8; R IFF = 54Ω, 1 5 Propagation elay t PHL C L1 = C L = 1pF 1 5 ns t PLH - t PHL ifferential Receiver Skew t SK Figures 4, 8; R IFF = 54Ω, C L1 = C L = 1pF 1 Maximum ata Rate f MX t SKEW, t SK 5% of data period.5 Mbps ns 3
MX348E/MX348E SWITCHING CHRCTERISTICS MX348E (V CC = V CC1 = V CC = V CC4 =V CC5 = +3.V to +3.6V, FS =, T = T MIN to T MX, unless otherwise noted. Typical values are at V CC = +3.3V and T = +5 C.) PRMETER SYMOL CONITIONS MIN TYP MX UNITS river Input to Output t PLH Figures 4, 6; R IFF = 54Ω, 1.5 3. µs Propagation elay t PHL C L1 = C L = 1pF 1. 3. Figures 4, 6; R river Output Skew t IFF = 54Ω, SKEW 3 1 ns C L1 = C L = 1pF Figures 4, 6; R river Rise or Fall Time t R, t IFF = 54Ω, F 1.. µs C L1 = C L = 1pF river Enable to Output High t ZH Figures 5, 7; C L = 1pF, S closed 1. 4.5 µs river Enable to Output Low t ZL Figures 5, 7; C L = 1pF, S1 closed 1. 4.5 µs river isable Time from Low t LZ Figures 5, 7; C L = 15pF, S1 closed 1.5 4.5 µs river isable Time from High t HZ Figures 5, 7; C L = 15pF, S closed. 4.5 µs Receiver Input to Output t PLH Figures 4, 8; R IFF = 54Ω,.6 3. Propagation elay t PHL C L1 = C L = 1pF 1.4 3. µs t PLH - t PHL ifferential Receiver Skew t SK Figures 4, 8; R IFF = 54Ω, C L1 = C L = 1pF 75 15 Maximum ata Rate f MX t SKEW, t SK 5% of data period 16 kbps Note 1: ll currents into device pins are positive; all currents out of device pins are negative. ll voltages are referenced to logic-side ground (GN1, GN), unless otherwise specified. Note : For E and I pin descriptions, see the lock iagram and the Typical pplication Circuit (Figure 1 for MX348E/MX348E). Note 3: Shutdown supply current is the current at V CC1 when shutdown is enabled. Note 4: Limit guaranteed by applying 15VRMS for 1s. Test voltage is applied between all pins on one side of the package to all pins on the other side of the package. For example, between pins 1 and 14, and 15 and 8. Note 5: pplies to peak current. See the Typical Operating Characteristics and the pplications Information section. ns 4
Typical Operating Characteristics (V CC_ = +3.3V, T = +5 C, Figure 1, unless otherwise noted.) IFFERENTIL OUTPUT VOLTGE (V) 3..9.8.7.6.5.4.3..1 RIVER IFFERENTIL OUTPUT VOLTGE vs. TEMPERTURE I = HIGH OR OPEN R L = 54Ω. -4-4 6 8 TEMPERTURE ( C) OUTPUT LOW VOLTGE (V).8.7.6.5.4.3. MX348E/E toc1 OUTPUT CURRENT (m) -1-9 -8-7 -6-5 -4-3 - -1 RECEIVER OUTPUT LOW VOLTGE vs. TEMPERTURE MESURE T ISO RV I = 8m OUTPUT CURRENT vs. RIVER OUTPUT HIGH VOLTGE -6-4 - 4 6 OUTPUT HIGH VOLTGE (V) MX348E/E toc4 OUTPUT HIGH VOLTGE (V) 5. 4.75 4.5 4.5 4. 3.75 3.5 MX348E/E toc OUTPUT CURRENT (m) 18 16 14 1 1 8 6 4 RECEIVER OUTPUT HIGH VOLTGE vs. TEMPERTURE MESURE T ISO RV I = 8m OUTPUT CURRENT vs. RIVER OUTPUT LOW VOLTGE 4 6 8 1 1 OUTPUT LOW VOLTGE (V) MX348E/E toc5 MX348E/E toc3 MX348E/MX348E.1-4 - 4 6 8 TEMPERTURE ( C) 3.5 3. -4-4 6 8 TEMPERTURE ( C) OUTPUT CURRENT (m) 8 7 6 5 4 3 OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTGE MESURE T ISO RV MX348E/E toc6 OUTPUT CURRENT (m) 8 7 6 5 4 3 OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTGE MESURE T ISO RV MX348E/E toc7 1 1 1.. 3. 4. 5. OUTPUT LOW VOLTGE (V) 1.. 3. 4. 5. IFFERENTIL OUTPUT VOLTGE (V) 5
MX348E/MX348E Typical Operating Characteristics (continued) (V CC_ = +3.3V, T = +5 C, Figure 1, unless otherwise noted.) MX348E RIVER INPUT () N RECEIVER OUTPUT () MX348E/E toc8 1ns/div CIRCUIT OF FIGURE, TERMINTION: 1Ω MX348E RIVER INPUT () N RECEIVER OUTPUT () MX348E/E toc11 I INPUT, V/div V/div, 74HC4, V/div I INPUT, V/div MX348E RIVER ENLE () N RECEIVER OUTPUT () MX348E/E toc9 1ns/div CIRCUIT OF FIGURE, TERMINTION: 1Ω MX348E RIVER ENLE (E ) N RIVER OUTPUT () MX348E/E toc1 E INPUT, 1V/div, 1V/div, V/div E 1V/div SUPPLY CURRENT (m) 35 3 5 15 1 5 3 5 MX348E SUPPLY CURRENT vs. SUPPLY VOLTGE E HIGH, 5Ω LO E LOW, I LOW, R L = E HIGH, 1Ω LO E LOW, I HIGH, R L = 3. 3. 3.4 3.6 3.8 SUPPLY VOLTGE (V) MX348E SUPPLY CURRENT vs. SUPPLY VOLTGE E HIGH, 5Ω LO MX348E/E toc1 MX348E/E toc13 1µs/div V/div, 74HC4, V/div µs/div V/div V/div SUPPLY CURRENT (m) 15 1 5 E LOW, I LOW, R L = 3. 3. 3.4 3.6 3.8 SUPPLY VOLTGE (V) E HIGH, 1Ω LO E LOW, I HIGH, R L = RIVER ENLE TIME (µs).5. 1.5 1..5 RIVER ENLE TIME vs. TEMPERTURE MX348E R L = 54Ω, I = MESURE FM E TO VLI OUTPUT MX348E MX348E/E toc14 RIVER ENLE TIME (µs). 1.5 1. RIVER ENLE TIME vs. TEMPERTURE MX348E R L = 54Ω, I = V MESURE FM E TO VLI OUTPUT MX348E MX348E/E TOC15-4 - 4 6 8 TEMPERTURE ( C).5-4 - 4 6 8 TEMPERTURE ( C) 6
Pin escription PIN NME FUNCTION PINS ON THE NONISOLTE SIE 1 V CC1 Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins, 1, and 14. V CC Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 1, and 14. 3, 4 1, oost-voltage Generator Outputs. See Figures 1 and. 5, 1 GN1, GN 6 FS Logic-Side Ground Inputs. Must be connected; not internally connected. Frequency Switch Input. If V FS = V CC, switch frequency is high; if FS =, switch frequency is low (normal connection). 7 S Power-Supply Shutdown Input. Must be connected to logic ground. 8 V CC3 oosted V+ Voltage Input. Must be connected as shown in Figures 1 and. 9 I river Input. With E high, a low on I forces output low and output high. Similarly, a high on I forces output high and output low. rives internal LE cathode through R1 (Table 1). 1 V CC4 Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1,, and 14. 11 E river-enable Input. The driver outputs, and, are enabled by bringing E high. The driver outputs are high impedance when E 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. rives internal LE cathode through R (Table 1). MX348E/MX348E 13 Receiver Output. If > by mv, is low; if < by mv, is high. Open collector; must have pullup (R3) to V CC (Table 1). 14 V CC5 Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1,, and 1. 7
MX348E/MX348E Pin escription (continued) PIN NME FUNCTION PINS ON THE ISOLTE RS-485/RS-4 SIE 15 ISO LE Isolated Receiver-Output LE node (Input). If > by mv, ISO LE is high; if < by mv, ISO LE is low. 16 ISO COM Isolated-Supply Common Input. Connect to ISO COM1. 17 ISO E RV Isolated river-enable rive Input. The driver outputs, and, are enabled by bringing E high. The driver outputs are high impedance when E 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. Open collector output; must have pullup (R4 in Figure 1) to ISO VCC and be connected to ISO E IN for normal operation (Table 1). 18 ISO V CC Isolated-Supply Positive Input Voltage. Connect to ISO V CC1. 19 ISO I RV ISO COM1 Isolated river-input rive. With E high, a low on I forces output low and output high. Similarly, a high on I forces output high and output low. Open-collector output; must have pullup (R5 in Figure 1) to ISO VCC and be connected to ISO I IN for normal operation (Table 1). Isolated-Supply Common Output. Connect to ISO COM. If RS-485 wires have a shield, connect ISO COM1 to shield through 1Ω resistor. 1 ISO E IN Isolated river-enable Input. Connect to ISO E RV for normal operation. ISO I IN Isolated river Input. Connect to ISO I RV for normal operation. 3 Noninverting river Output and Noninverting Receiver Input 4 ISO RV Isolated Receiver-Output rive. Connect to ISO LE through R6 (Table 1 and Figure 1). 5 Inverting river Output and Inverting Receiver Input 6 ISO V CC1 Isolated Supply Positive Output Voltage. Connect to ISO V CC. 7, 8 C, C1 Internal Connections. Leave these pins unconnected. Note: For E and I pin descriptions, see etailed lock iagram. 8
etailed escription The MX348E/MX348E are electrically isolated, RS-485/RS-4 data-communications interface solutions. Transceivers, optocouplers, a power driver, and a transformer are in one standard 8-pin PIP package. Signals and power are internally transported across the FS LOGIC I/O V IN +3.V TO +3.6V OSC 1.1MHz/ 1.6MHz I E V CC3 R1* R* T C1 µf F/F OOSTE V+ C3.1µF R3* Q Q S C.1µF 1, 1N914 MX845 V CC1 V CC 1 GN1 FS S V CC3 I N N GN1 1 3 4 5 6 7 8 9 V CC4 1 E 11 GN 1 13 V CC5 14 1 MX348E/E MX845 MX1487E MX487E isolation barrier (Figure 1). 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 +3.3V supply on the logic side powers both sides of the interface. 8 C1 (MKE NO CONNECTION) 7 C (MKE NO CONNECTION) 6 5 4 3 1 19 18 17 16 15 ISO I IN ISO E IN ISO RV ISO V CC1 ISO RV ISO I IN ISO E IN ISO COM1 ISO I RV ISO V CC ISO E RV ISO COM ISO LE ISO COM1 ISO V CC1 RE R6* R R7* R4* R5* MX348E: MX485E MX348E: MX487E EXTERNL RS-485/RS-4 WIRING SH R8 1Ω TERMINTING RESISTOR (ONE RESISTOR ON ECH EN) TWISTE PIR TO OTHER TRNSCEIVERS SHIEL (OPTIONL) TWISTE PIR TO OTHER TRNSCEIVERS SHIEL (OPTIONL) NOTE: RESISTOR R8 PTECTS THE MX348E FM TRNSIENT CURRENTS ETWEEN SHIEL N N. R L R L MX348E/MX348E ISOLTION RRIER ISOLTION COMMON *SEE TLE 1. Figure 1. lock iagram LOGIC GUN C4 7pF 4kV Table 1. Pullup and LE rive Resistors PRT R1 (Ω) R (Ω) R3 (Ω) R4 (Ω) R5 (Ω) R6 (Ω) MX348E 1 1 68 36 1 MX348E 1 1 36 36 R7 (Ω) Open 43 9
MX348E/MX348E The MX348E features reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission at data rates up to 16kbps. The MX348E s driver slew rates are not limited, allowing transmission rates up to.5mbps. The frequency-select FS is connected to GN_ in normal operation, which selects a switching frequency of approximately 6kHz. Connect to high for a higher 9kHz switching frequency. rivers are short-circuit current limited and are protected against excessive power dissipation by thermal I E 74HC4 17 18 3 9 4 6 8 15 13 V IN +3.V TO +3.6V 16 14 1 5 7 C1 µf 6V RIVER INPUT RIVER ENLE 11 RECEIVER OUTPUT C.1µF OOSTE V+ C3.1µF R1* R* R3* 1, 1N914 V CC1 V CC 1 GN1 FS S V CC3 I 1 3 4 5 6 7 8 9 V CC4 1 E 11 GN 1 13 V CC5 14 MX348E/E MX845 MX1487E MX487E 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 output if the input is open circuit. The driver outputs are enabled by bringing E high. river-enable times are typically 5ns for the MX348E and 1µs for the MX348E. llow time for the devices to be enabled before sending data. When enabled, driver outputs function as line drivers. river outputs are high impedance when E is low. While outputs are high impedance, they function as line receivers. 8 C1 (MKE NO CONNECTION) 7 C (MKE NO CONNECTION) 6 5 4 3 1 19 18 17 16 15 ISO V CC1 ISO RV ISO I IN ISO E IN ISO COM1 ISO I RV ISO V CC ISO E RV ISO COM ISO LE R6* R7* R4* R5* EXTERNL RS-485/RS-4 WIRING SH R8 1Ω TERMINTING RESISTOR (ONE RESISTOR ON ECH EN) TWISTE PIR TO OTHER TRNSCEIVERS SHIEL (OPTIONL) TWISTE PIR TO OTHER TRNSCEIVERS SHIEL (OPTIONL) NOTE: RESISTOR R8 PTECTS THE MX348E FM TRNSIENT CURRENTS ETWEEN SHIEL N N. R L R L 1 ISOLTION RRIER ISOLTION COMMON *SEE TLE 1. LOGIC GUN C4 7pF 4kV Figure. Typical pplication Circuit 1
Test Circuits Figure 3. river C Test Load V O R R V OC OUTPUT UNER TEST C L 5Ω +3.3V E I ISOLTION RRIER C L1 R IFF C L Figure 4. river/receiver Timing Test Circuit S1 S V I ISO V CC1, ISO V CC ISOLTION RRIER R +3.3V R3 MX348E/MX348E Figure 5. river Timing Test Load Switching Waveforms V CC _ -.4V VCC _ -.4V I V IFF V O -V O V O 1/ V O t R 1% t PLH t PHL V IFF = V - V 9% 9% t SKEW = t PLH - t PHL t F V CC _ -.4V 1/ VO 1% V CC _ -.4V VCC _ -.4V E, V OL, t ZL t LZ.3V OUTPUT NORMLLY LOW OUTPUT NORMLLY HIGH.3V t ZH t HZ V CC _ -.4V V OL +.5V V OH -.5V Figure 6. river Propagation elays and Transition Times Figure 7. river Enable and isable Times 11
MX348E/MX348E Switching Waveforms (continued) V - V V OH V OL V I -V I 1.5V t PHL Figure 8. Receiver Propagation elays Table. Transmitting INPUTS OUTPUT t PLH 1.5V INPUT t SK = t PLH - t PHL Function Tables E I 1 1 1 1 1 X X = on t care. Table 3. Receiving E INPUTS - High Impedance OUTPUTS High Impedance OUTPUT R O +.V -.V 1 Inputs open The MX348E/MX348E withstand 16VRMS (1 min) or 156VRMS (1s). The isolated outputs of these devices meet all RS-485/RS-4 specifications. oost Voltage The MX348E/MX348E require external diodes on the primary of the transformer to develop the boost voltage for the power oscillator. In normal operation, whenever one of the oscillator outputs (1 and ) goes low, the other goes to approximately double the supply voltage. Since the circuit is symmetrical, the two outputs can be combined with diodes, filtered, and used to power the oscillator itself. The diodes on the primary side may be any fast-switching, small-signal diodes, such as the 1N914, 1N4148, or CMP838. The nominal value of the primary filter capacitor C3 is.1µf. river 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 whole common-mode voltage 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. Resistor R8 (Figures 1 and ) provides additional protection by current limiting between the shield and the two signal wires. In the event that shielded cable is used and an external voltage or transient is inadvertently applied between the shield and the signal wires, the MX348E/MX348E can be damaged. lthough unlikely, this condition can occur during installation. The MX348E/MX348E provide electrical isolation between logic ground and signal paths; they do not provide isolation from external shields and the signal paths. When in doubt, do not connect the shield. The MX348E/MX348E can be damaged if resistor R8 is shorted out. pplications Information The MX348E/MX348E provide extra protection against ES. The MX348E/MX348E are intended for harsh environments where high-speed communication is important. These devices eliminate the need for transient suppressor diodes or the use of discrete protection components. The standard (non-e) MX348/MX348 are recommended for applications where cost is critical. 1
Machine Model The Machine Model for ES tests all pins using a pf storage capacitor and zero discharge resistance. Its objective is to simulate the stress caused by contact that occurs with handling and assembly during manufacturing. Of course, all pins require this protection during manufacturing not just inputs and outputs. Therefore, after PC board assembly, the Machine Model is less relevant to l/o ports. The MX348E/MX348E are designed for bidirectional data communications on multipoint bus-transmission lines. Figure 11 shows a typical network application circuit. 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 slewrate-limited MX348E is more tolerant of imperfect termination and stubs off the main line. The MX348E/MX348E are specified and characterized using the resistor values shown in Table 1. ltering the recommended values can degrade performance. The I and E inputs are the cathodes of LEs whose anodes are connected to VCC. These points are best driven by a +3.3V CMOS-logic gate with a series resistor to limit the current. The resistor values shown in Table 1 are recommended when the 74HC4 gate or equivalent is used. I and E are intended to be HIGH- VOLTGE C SOURCE R C 1MΩ CHRGE-CURRENT LIMIT RESISTOR Cs 1pF R 15Ω ISCHRGE RESISTNCE STORGE CPCITOR Figure 9. Human ody ES Test Model EVICE UNER TEST ±15kV ES Protection s with all Maxim devices, ES-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs have extra protection against static electricity. Maxim s engineers developed state-of-the-art structures to protect these pins against ES of ±15kV without damage. The ES structures withstand high ES in all states: normal operation, shutdown, and power-down. fter an ES event, Maxim s MX348E/MX348E keep working without latchup. n isolation capacitor of 7pF 4kV should be placed between ISO COM and logic ground for optimal performance against an ES pulse with respect to logic ground. ES protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family are characterized for protection to ±15kV using the Human ody Model. ES Test Conditions The +15kV ES test specifications apply only to the,, Y, and Z I/O pins. The test surge may be referenced to either the ISO COM or to the nonisolated GN (this presupposes that a bypass capacitor is installed between V CC and the nonisolated GN). Human ody Model Figure 9 shows the Human ody Model, and Figure 1 shows the current waveform it generates when discharged into a low impedance. This model consists of a MPERES I P 1% 9% 36.8% 1% t RL TIME t L CURRENT WVEFORM Figure 1. Human ody Model Current Waveform PEK-TO-PEK RINGING (NOT RWN TO SCLE) 1pF capacitor charged to the ES voltage of interest, which is then discharged into the test device through a 1.5kΩ resistor. Ir MX348E/MX348E 13
MX348E/MX348E driven through a series current-limiting resistor. irectly grounding these pins destroys the device. Reliability These products contain transformers, optocouplers, and capacitors, in addition to several monolithic ICs and diodes. s such, the reliability expectations more closely represent those of discrete optocouplers, rather than the more robust characteristics of monolithic silicon ICs. The reliability testing programs for these multicomponent devices may be viewed on the Maxim website (www.maxim-ic.com) under Technical Support, Technical Reference, Multichip Products. Table 4. Maxim s ±15kV ES-Protected Isolated RS-485 Product Family PRT NO. OF Tx/Rx GURNTEE T RTE (Mbps) FULL/HLF UPLEX SLEW-RTE LIMITE NO. OF Tx/Rx ON US SUPPLY VOLTGE (V) MX148E 1/1.5 Half No 18 5. MX148EC 1/1.5 Half Yes 18 5. MX149E 1/1.5 Full No 3 5. MX149E 1/1.5 Full Yes 3 5. MX348E 1/1.5 Half No 18 3.3 MX348E 1/1.5 Half Yes 18 3.3 14
74HC4 18 I 3 17 E 9 *SEE TLE 1. 1 RE V IN +3.V TO +3.6V 4 6 8 15 13 16 14 1 5 7 R E C1 µf 6V RIVER INPUT RIVER ENLE I 11 RECEIVER OUTPUT C.1µF OOSTE V+ C3.1µF R1* R* R3* RE 1, 1N914 R E LOGIC GUN V CC1 V CC 1 GN1 FS S V CC3 TERMINTING RESISTOR (ONE RESISTOR ON ECH EN) I 1 3 4 5 6 7 8 9 V CC4 1 E GN 11 1 13 V CC5 14 I MX348E/E MX845 MX1487E MX487E ISOLTION RRIER C4 7pF 4kV 1Ω ISO V CC1 ISO RV ISO I IN ISO E IN ISO COM1 ISO I RV ISO V CC ISO E RV ISO COM ISO LE R RE TERMINTING RESISTOR (ONE RESISTOR ON ECH EN) 8 C1 (MKE NO CONNECTION) 7 C (MKE NO CONNECTION) 6 5 4 3 1 19 18 17 16 15 R6* R7* R4* R5* ISOLTION COMMON I E 1Ω SH R8 1Ω SHIEL (OPTIONL) NOTE: RESISTOR R8 PTECTS THE MX348E FM TRNSIENT CURRENTS ETWEEN SHIEL N N. MX348E/MX348E Figure 11. Typical RS-485/RS-4 Network 15
MX348E/MX348E Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 1 L N 1 e TOP VIEW 1 1 3-15 E E1 e e C INCHES IM 1 MIN -.15 MX. - MIN -.39 MX 5.8 -.15.175 3.18 4.45 3.8.3. 1 C 1 E.55.16.45.8.5.6.65.1.9.65 MILLIMETERS 1.4.41 1.14.1.13 15.4.51 1.65.3. 15.87 E1.55.575 13.34 14.61 e.1 SC.54 SC e.6 SC 15.4 SC e -.7-17.78 L.1.15 3.5 3.81 VRITIONS: IM INCHES MILLIMETERS MIN MX MIN MX N MS11 1.3 1.7 31.4 3.6 4 1.43 1.47 36.3 37.34 8.5.75 51.44 5.71 4 C PIPW.EPS FNT VIEW SIE VIEW PPRIETRY INFORMTION TITLE: PCKGE OUTLINE,.6" PIP PPVL OCUMENT CONTL NO. REV. 1-44 1 1 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. 16 Maxim Integrated Products, 1 San Gabriel rive, Sunnyvale, C 9486 48-737-76 6 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.