Description

The MAX1480A/MAX1480B/MAX1480C/MAX1490A/MAX1490B 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 DIP package. A single +5V supply on the logic side powers both sides of the interface.

The MAX1480B/MAX1480C/MAX1490B 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 250kbps.

The MAX1480A/MAX1490A driver slew rate is not limited, allowing transmission rates up to 2.5Mbps. The MAX1480A/B/C are designed for half-duplex communication, while the MAX1490A/B 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 (RO low for the MAX1480A/B/C, RO high for the MAX1490A/B) if the input is open circuit.

The MAX1480A/MAX1480B/MAX1480C/MAX1490A/ MAX1490B typically withstand 1600VRMS (1 minute) or 2000VRMS (1 second). Their isolated outputs meet all RS-485/RS-422 specifications. The MAX1490A/B are available in a 24-pin DIP package.

 

Features

±15kV ESD-Protected,Isolated RS-485/RS-422 Data Interfaces

ABSOLUTE MAXIMUM RATINGS:

With Respect to GND_

Supply Voltage (VCC_):  -0.3V to +6V

Control Input Voltage (SD, FS):  -0.3V to (VCC_ + 0.3V)

Receiver Output Voltage (RO, RO):  -0.3V to (VCC_ + 0.3V)

Output Switch Voltage (D1, D2):  +12V

With Respect to ISO COM_

Control Input Voltage (ISO DE_ ):  -0.3V to (ISO VCC_ + 0.3V)

Driver Input Voltage (ISO DI_ ):  -0.3V to (ISO VCC_ + 0.3V)

Receiver Output Voltage (ISO RO_):  -0.3V to (ISO VCC_ + 0.3V)

Driver Output Voltage (A, B, Y, Z ):  -8V to +12.5V

Receiver Input Voltage (A, B):  -8V to +12.5V

LED Forward Current (DI, DE, ISO RO LED):  50mA

Continuous Power Dissipation (TA = +70℃)

24-Pin Plastic DIP (derate 8.7mW℃ above +70℃):  696mW

Operating Temperature Ranges

MAX1480_EPI/MAX1490_EPG:  -40℃ to +85℃

Storage Temperature Range :  -65℃ to +160℃

Lead Temperature (soldering, 10s):  +300℃

 

Applications

Isolated RS-485/RS-422 Data Interface

Transceivers for EMI-Sensitive Applications

Industrial-Control Local Area Networks

Automatic Test Equipment

HVAC/Building Control Networks

 

Detailed Description

The MAX1480A/MAX1480B/MAX1480C/MAX1490A/MAX1490B 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 DIP package (24- pin for the MAX1490A/B) provide a complete interface. Signals and power are internally transported across the isolation barrier (Figures 1, 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. A single +5V supply on the logic side powers both sides of the interface.The MAX1480A/B/C offer half-duplex communications while the MAX1490A/B feature full-duplex communication. The functional input/output relationships are shown in Tables 3–6.

The MAX1480B/MAX1480C/MAX1490B feature reducedslew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission at data rates up to 250kbps. The MAX1480A/MAX1490A driver slew rate is not limited, allowing transmission rates up to 2.5Mbps.

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 4mA, and by up to 8mA when fully loaded. For optimal performance and minimal supply current, connect FS to VCC_ 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 RO (logic-low RO) output if the input is open circuit.