MAX485MJA - 2.5 Mb/s RS-485/RS-422 Transceiver, 8-CERDIP | Analog Devices
MPN: MAX485MJA ✓ פעילMAX485MJA סקירה
An RS-485 transceiver is the physical-layer bridge between a logic-level UART or microcontroller and a balanced, multi-drop cable bus. RS-485 belongs to the differential signaling family of interface ICs, sitting between the transceiver category and the wider Interface ICs > Drivers/Receivers/Transceivers hierarchy. Because differential signaling sends a signal and its complement over a twisted pair, it rejects common-mode noise, allows long cable runs, and supports multiple nodes on one bus, making it the de facto standard for industrial automation, building controls and instrumentation networks.
Key features of the MAX485MJA include a low-power slew-rate-limited driver that reduces EMI and ringing on slow edges, one driver and one receiver per package, and a 2.5 Mb/s data rate as listed by distributors for the MAX485 series. The /RE and DE pins give the designer independent control over driver enable and receiver enable, allowing half-duplex bus turnaround control from a single microcontroller pin. Operating over the extended industrial temperature range, the CERDIP-8 mechanical format gives long-term availability for rugged and legacy industrial platforms.
The device implements a classic current-mode differential driver with a failsafe bias network so that an unpowered or disconnected node does not clamp the bus, plus a fail-safe receiver stage that interprets an open or shorted bus as a defined logic state. The 8-pin pinout (RO, /RE, DE, DI, GND, A, B, VCC) is shared across the entire MAX48x family, which simplifies cross-referencing and second sourcing across ceramic, plastic and surface-mount variants.
Typical applications include industrial RS-485 field buses such as Modbus RTU networks, building HVAC and lighting controllers, PLC and data-acquisition module interfaces, POS terminals and industrial instrumentation, and retrofit of legacy 2.5 Mb/s RS-485 equipment where a ceramic military-temperature package is required.
When designing with the MAX485MJA, note that the 8-pin package leaves no dedicated fail-safe bias resistor footprint; many designs add 100 ohm to 220 ohm termination resistors and a fail-safe bias network externally. Because the CERDIP-8 body is larger than a standard PDIP-8, check board mechanicals and pin-hole spacing, and keep the A and B differential pair away from switching nodes and high-current returns to preserve common-mode margin.
This page consolidates verified distributor pricing, a drop-in cross-reference set, pin-level detail and applied design guidance that is not available from a single manufacturer datasheet, helping engineers qualify this part quickly for both new and legacy industrial designs.
חלופות תחליף ישיר עבור MAX485MJA — אותו מארז, תואם פין-לפין. חלקים במארז שונה הדורשים עיבוד מחדש של ה-PCB אינם נכללים.
וריאנטים בסדרה זו
דגמים מאותה סדרה התואמים Drop-in עם MAX485MJA (אותו גורם צורה וטביעת רגל) — שונים ב Package, Product Type.
MAX485MJA/883B
✅ Drop-In ⚠️ מפרטים לא מאומתים📋 חלופה להתייחסות (לא בקטלוג)
MAX483MJA/883B
✅ Drop-In📋 חלופה להתייחסות (לא בקטלוג)
MAX481MJA
✅ Drop-In ⚠️ מפרטים לא מאומתים📋 חלופה להתייחסות (לא בקטלוג)
LTC485CN8
✅ Drop-In📋 חלופה להתייחסות (לא בקטלוג)
SN75176BP
✅ Drop-Inצור קשר לקבלת מחיר
הצג גיליון נתונים ←MAX485MJA מפרטים
| Product Type | RS-485/RS-422 transceiver (1 driver, 1 receiver) |
| קצב נתונים | 2.5 Mb/s |
| Number of Drivers | 1 |
| Number of Receivers | 1 |
| Duplex | Half-duplex |
| Standards Supported | RS-485, RS-422 |
| מארז | 8-CERDIP (military ceramic dual-inline) |
| מספר פינים | 8 |
| סגנון הרכבה | Through Hole |
| Driver Architecture | Slew-rate-limited, low-power |
| RoHS Compliance | Not compliant per distributor listing (RoHS: N) |
| Automotive Qualification (AEC-Q100) | Not applicable |
| Manufacturer Document | MAX485-MAX491 datasheet (data sheet covers MAX481, MAX483, MAX485, MAX487-MAX491 and MAX1487) |
תצורת פינים של MAX485MJA
| פין 1 | RO — Receiver output (logic level data from the bus) |
| פין 2 | /RE — Receiver enable, active low (high disables receiver output) |
| פין 3 | DE — Driver enable (high enables the differential driver) |
| פין 4 | DI — Driver input (logic level data to be transmitted) |
| פין 5 | GND — Ground reference for the transceiver |
| פין 6 | A — Non-inverting bus driver output / receiver input |
| פין 7 | B — Inverting bus driver output / receiver input |
| פין 8 | VCC — Positive supply voltage for the transceiver |
יישומים טיפוסיים
MAX485MJA מתאים עבור 6 יישוםs: Industrial Modbus RTU Field Bus, Building HVAC and Lighting Control Networks, PLC and Data Acquisition Module Interfaces, POS Terminals and Retail Peripherals, Legacy Industrial Equipment Retrofit, RS-422 Point-to-Point Long-Haul Links.
Industrial Modbus RTU Field Bus
The MAX485MJA is a natural fit for Modbus RTU field bus nodes because the RS-485 differential pair carries the classic UART framing at 9.6 kbit/s to 115.2 kbit/s with high noise immunity in factory environments. The MAX485 series drives 2.5 Mb/s, so a 115.2 kbit/s bus sits far below the slew-rate-limited driver's capability and the receiver has ample margin for the differential thresholds. Because this is an 8-pin CERDIP part with no external bias pads, the design must add 120 ohm termination resistors at both bus ends plus a fail-safe bias network (typically 680 ohm pull-up on A, 680 ohm pull-down on B) so an idle or disconnected bus reads as a defined logic state. The ceramic package is a bonus for equipment operating in wide-temperature plant rooms or on vibration-prone machinery.
מומלץ
Building HVAC and Lighting Control Networks
In building automation, the MAX485MJA links thermostats, dimmers and lighting controllers over an RS-485 daisy chain running hundreds of metres through walls and ceilings. Differential signaling keeps the bus immune to the switching noise generated by relay coils, contactors and dimming stages in the same electrical cabinet, and the low-power slew-rate-limited driver limits EMI radiated from the cable itself. The 2.5 Mb/s capability gives headroom for building controllers that also carry occupancy-sensor traffic alongside lighting commands. For field-serviceable building controllers, the ceramic CERDIP-8 package resists temperature cycling better than the plastic MAX485EPA, and the shared MAX48x 8-pin pinout means a maintenance replacement can be a MAX485MJA/883B or even a plastic MAX485 variant without any board change.
מומלץ
PLC and Data Acquisition Module Interfaces
Data acquisition and PLC front-end modules typically need to bridge a low-power MCU or DSP UART to an isolated or non-isolated RS-485 field link, and the MAX485MJA provides exactly one driver and one receiver for that half-duplex role. The separate DE and /RE pins let the host controller assert the driver only during transmission, which is essential on shared multi-drop acquisition buses where more than one node may transmit. At 2.5 Mb/s the device also supports high-speed burst acquisition backhaul over short cable runs. Because the MAX485MJA shares the standard MAX48x 8-pin pinout, designers can use the identical PCB footprint for the high-volume plastic MAX485ESA and the ceramic MAX485MJA, keeping a single board revision qualified across both commercial and ruggedized builds.
מומלץ
POS Terminals and Retail Peripherals
Retail point-of-sale terminals and barcode scanners frequently use RS-485 for in-store peripherals such as scales, card readers and customer displays, where cable lengths inside the counter and proximity to switching power supplies create a noisy environment. The MAX485MJA's differential receiver rejects the common-mode offsets and ripple that would corrupt a single-ended link, and the slew-rate-limited driver keeps the in-store cable from radiating into adjacent electronics. For terminals deployed in shipping containers, kitchens or unheated stock rooms, the ceramic temperature grade of the MAX485MJA is valuable, while the identical 8-pin DIP footprint allows a single assembled board to be certified with either the ceramic MAX485MJA or the lower-cost plastic MAX485EPA depending on the customer's environment requirement.
מומלץ
Legacy Industrial Equipment Retrofit
Retrofitting an older machine or test bench usually means reusing a board whose schematic calls for a ceramic 8-pin military MAX485. The MAX485MJA preserves that exact footprint, so an engineer can replace a long-obsolete or hard-to-source part without redesigning the PCB or changing the socket. Because the part is a single driver plus single receiver in the standard MAX48x arrangement, it can also substitute for early RS-422 one-driver/one-receiver cards when the differential pair is wired to A and B in the usual manner. Note that the MAX485MJA is listed RoHS 'N' by distributors, so for new designs constrained by RoHS the MAX485ECSA+ or MAX485EPA+ are preferable; for legacy spares and repair stock, the MAX485MJA remains the correct fit.
מומלץ
RS-422 Point-to-Point Long-Haul Links
Although the MAX485MJA is marketed for RS-485, the one-driver/one-receiver topology also supports full-duplex RS-422 links when the driver and receiver are used on separate pairs, and the differential signaling gives long cable reach with good noise immunity. This is common in instrumentation and test equipment where a controller talks to a remote sensor head over a shielded twisted pair. The MAX485 series' 2.5 Mb/s data rate comfortably covers the kilobit-to-megabit range typically used in such links, and the ceramic package suits instrumentation deployed in unheated enclosures. Designers should still terminate the RS-422 pair at the receiver end and provide the differential driver with adequate common-mode headroom for the cable length and grounding scheme in use.
מומלץ
סיכום מוצרים מומלצים
נתוני עזר הנדסיים עבור MAX485MJA — השוואה, הנחיות תכנון ומידע על תאימות.
מדריך בחירה
השוואה עם חלופות
| פרמטר | מוצר זה | MAX485MJA/883B | MAX483MJA/883B | MAX481MJA | LTC485CN8 | SN75176BP |
|---|---|---|---|---|---|---|
| Package | 8-CERDIP (ceramic DIP) | 8-CERDIP - same | 8-CERDIP - same | 8-CERDIP - same | 8-CERDIP / 8-pin DIP - same 8-pin outline | 8-CERDIP / 8-pin DIP - same 8-pin outline |
| Brand | Analog Devices (Maxim Integrated) | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Texas Instruments |
| Transceiver Configuration | 1 driver / 1 receiver, half-duplex | 1 driver / 1 receiver, half-duplex | 1 driver / 1 receiver, half-duplex | 1 driver / 1 receiver, half-duplex | 1 driver / 1 receiver, half-duplex | 1 driver / 1 receiver, half-duplex |
| Data Rate | 2.5 Mb/s | 2.5 Mb/s | Approximately 250 kbit/s (low-power MAX48x member) | Approximately 250 kbit/s (lowest-power MAX48x member) | 2.5 Mb/s class | 1 Mb/s (about -60% versus MAX485) |
| Standards Supported | RS-485, RS-422 | RS-485, RS-422 | RS-485, RS-422 | RS-485, RS-422 | RS-485, RS-422 | RS-485 |
| Mounting Style | Through Hole | Through Hole | Through Hole | Through Hole | Through Hole | Through Hole |
| Special Features | Slew-rate-limited low-power driver, ceramic military package | Slew-rate-limited driver plus 883B military screening | Ultra-low-power operation for reduced-speed buses | Lowest quiescent power member of the MAX48x family | 8-pin DIP option with slew-rate-limited driver | Widely sourced RS-485 driver with enable pins |
| Data Rate Margin vs MAX485MJA | Reference 2.5 Mb/s | 0% difference | Approximately -90% | Approximately -90% | 0% difference | Approximately -60% |
מבדילים עיקריים
- Ceramic military-package build in the standard MAX48x 8-pin pinout (לעומתMAX485EPA+)
- Higher listed data rate than the low-power MAX48x ceramic siblings (לעומתMAX483MJA/883B)
- Ceramic package availability for the MAX485 function where plastic supply is thin (לעומתSN75176BP)
הערות תכנון
The MAX485MJA 8-pin CERDIP footprint provides no dedicated fail-safe bias resistor pads, so an idle or disconnected bus can float into an undefined logic state. Most industrial designs therefore add a discrete fail-safe network at one location on the bus - typically 680 ohm pulling the A line high and 680 ohm pulling the B line low with a 100 nF capacitor to ground at the midpoint - alongside 120 ohm termination resistors at both physical bus ends. Adding these parts directly on the transceiver board (or on a small termination module) is what turns a bare MAX485MJA into a robust multi-drop RS-485 node.
Because the MAX485MJA is a ceramic CERDIP-8 rather than a standard plastic PDIP-8, verify the mechanical drawing before committing to a socket or direct solder footprint. Ceramic military packages are typically taller and may use a different row spacing than the common 0.300 inch plastic DIP, and the ceramic body is more tolerant of thermal cycling but more sensitive to mechanical shock. Keep the A and B traces as a tightly coupled, continuous differential pair over the full run to the connector, provide a solid ground plane reference beneath them, and route them away from switching converter loops, relay contacts and high-current return paths to preserve common-mode margin.
Slew-rate limiting reduces EMI, but it also means the edge rate, not the nominal bit rate, sets your usable bandwidth. When you need headroom, keep cable runs short and use twisted-pair with a characteristic impedance near 120 ohm, and prefer terminating only the two physical ends of the bus even if intermediate nodes exist. If the bus is noisy, check the receiver threshold margin by measuring the differential voltage across A and B at the far end while the far node transmits; a healthy RS-485 link should show at least 200 mV of differential signal, and anything less points to termination, stub-length or grounding problems rather than to the transceiver itself.
Estimated: with a 5 V supply, a 1 Mbaud short-distance link and roughly 50 mA of average bus current at the driver, the MAX485MJA dissipation is on the order of 5 V x 50 mA = 0.25 W for the logic side, plus driver output dissipation during transmission. The dominant thermal risk in a ceramic DIP is the socket-to-board heat path rather than the die itself, so for high duty-cycle transmit at long cable lengths, place the transceiver near the connector, keep the ground return short and copper-heavy, and check the ambient temperature rise inside the enclosure. Because the MAX485 series is a low-power design by definition, most applications dissipate well under 1 W and need no heatsinking.
מידע על תאימות
Distributor comparison data for MAX485MJA lists RoHS as 'N' (not compliant), unlike the RoHS-compliant MAX485ECSA+. REACH, lead-free, halogen-free and conflict-minerals status are not published in the verified distributor records and are therefore marked unknown. The MAX485MJA is a military ceramic-DIP part and is not AEC-Q100 qualified.
