Allgemeine Beschreibung

The MAX13085E +5.0V, ±15kV ESD-protected, RS-485 transceiver features one driver and one receiver. The device includes fail-safe circuitry, guaranteeing a logic high receiver output when receiver inputs are open or shorted. The receiver outputs a logic high if all transmitters on a terminated bus are disabled (high impedance).

The MAX13085E includes a hot-swap capability to eliminate false transitions on the bus during power-up or hot insertion.

The MAX13085E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps.

The MAX13085E is ideal for half-duplex communications and it draws 1.2mA of supply current when unloaded or when fully loaded with the drivers disabled. The MAX13085E has a 1/8-unit load receiver input impedance, allowing up to 256 transceivers on the bus.

The MAX13085E is available in an 8-pin SO and PDIP packages.

 

Anwendungen

Utility Meters

Lighting Systems

Industrielle Steuerung

Telekommunikation

Security Systems

Instrumentierung

Profibus

 

Eigenschaften

+5.0V Operation

Extended ESD Protection for RS-485 I/O Pins ±15kV

Human Body Model

True Fail-Safe Receiver While Maintaining

EIA/TIA-485 Compatibility

Hot-Swap Input Structures on DE and RE

Enhanced Slew-Rate Limiting Facilitates

Error-Free Data Transmission

Niedrigstrom-Abschaltmodus

Allow Up to 256 Transceivers on the Bus

Available in Industry-Standard 8-Pin SO and PDIP Packages

 

More Information

Detaillierte Beschreibung

The MAX13085E high-speed transceiver for RS-485 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 MAX13085E also features a hot swap capability allowing line insertion without erroneous data transfer (see the Hot-Swap Capability section). The MAX13085E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps.

The MAX13085E is a half-duplex transceiver and operates from a single +5.0V 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 MAX13085E 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 -50mV and -200mV. If the differential receiver input voltage (A – B) is greater than or equal to -50mV, RO is logic-high. If (A – B) is less than or equal to -200mV, RO is logic-low. In the case of a terminated bus with all transmitters disabled, the receiver’s differential input voltage is pulled to 0V by the termination. With the receiver threshold of the MAX13085E, this results in a logic-high with a 50mV minimum noise margin. Unlike previous fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA- 485 standard.

±30kV ESD Protection

As 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 MAX13085E have extra protection against static electricity. Maxim’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, the MAX13085E keeps working without latchup or damage.

ESD protection can be tested in various ways. The transmitter output and receiver input of the MAX13085E are characterized for protection to the following limits:

±15kV unter Verwendung des Human Body Model

±8kV using the Contact Discharge method specified

in IEC 61000-4-2

±15kV using the Air-Gap Discharge method specified

in IEC 61000-4-2