These Intersil RS-485 /RS-422 devices are BiCMOS 3.3V compliant with RS-485 and RS-422 balanced communication standards. Unlike competing devices, this Intersil family is specified as a 10% tolerance supply (3V to 3.6V). The ISL83483 and ISL83488 use slew rate limiting drivers to reduce EMI and reduce undue reflections in terminated transmission lines or unterminated spool multidrop and multidrop applications. By using the ISL83485, ISL83490 or ISL83491, it features higher conversion rates. Logic inputs such as DI and DE accept more than 5.5V, making it compatible with 5V logic families. The receiver (Rx) input has a "fail-on-open" design that ensures a logic high output if the Rx input is floating. All devices provide a "single-unit load" to the RS-485 bus, which allows up to 32 transceivers on the network. The driver (Tx) outputs are short-circuit protected, even for voltages exceeding the supply voltage. In addition, the thermal shutdown circuit on the chip prohibits sending the output to prevent damage if the power dissipation is excessive. The ISL83488, ISL83490, ISL83491 are configured for full duplex (separate Rx input and Tx output pins) applications. The ISL83488 and ISL83490 save space 8 lead-package output disable functionality for applications that do not require Rx and Tx (eg point-to-point and RS-422). The half-duplex configuration (ISL83483, ISL83485) multiplexes the receive input and transmit output, providing the transceiver with receive and Tx disable functions in an 8-lead package.

feature

Single power supply +3.3V power supply (10% tolerance)

Interoperable with 5V logic

high data rate. up to 10Mbps

Single unit load allows up to 32 devices on the bus

Slew rate limited version transfer with no error data (ISL83483, ISL83488). up to 250kbps

Low current shutdown mode (ISL83483, ISL83485, ISL83491). 15mA

-7V to +12V Common Mode Input Voltage Range

Tri-state Rx and Tx outputs (except ISL83488, ISL83490)

10ns propagation delay, 1ns skew (ISL83485, ISL83490, ISL83491)

Full-duplex and half-duplex pinouts

Drive Current Limit and Thermal Shutdown Overload Protection

Lead free available

application

factory automation

safety net

Building Environment Control System

Industrial/Process Control Networks

Level translator (eg RS-232 to RS-422)

RS-232 "Extension Cable"

Absolute Maximum Ratings Thermal Information

VCC is grounded. 7 volts

Input voltage

DI, DE, RE. -0.5V to +7V

input/output voltage

A, B, Y, Z. -8V to +12.5V

reverse osmosis. -0.5V to (VCC+0.5V)

Short circuit duration Y, Z. continuously

operating conditions

temperature range

ISL834Xix. -40oC to 85oC

Thermal Resistance (Typical, Note 1) θJA (oC/W)

8 Ld SOIC package. 170

8 Ld PDIP packets. 140

14 Ld SOIC package. 130

14 Ld PDIP packets. 105

Maximum Junction Temperature (Plastic Packaging). 150 degrees Celsius

Maximum storage temperature range. -65 degrees Celsius to 150 degrees Celsius

Maximum lead temperature (10s for soldering). 300 degrees Celsius

(SOIC - lead only)

CAUTION: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a pressure rating and operation

Installation under the above or any other conditions stated in the operating section of this specification is not implied.

Note:

1. θJA is measured with components mounted on a low-efficiency thermal conductivity test board in free air.

Electrical specification test conditions: VCC=3V～3.6V; unless otherwise specified. The typical value is VCC=3.3V, TA=25oC,

Electrical specification test conditions: VCC=3V～3.6V; unless otherwise specified. Typical value is VCC=3.3V, TA=25oC, Note 2 (continued) Note 2

notes:

2. All current entering the device pins is positive; all current flowing out of the device pins is negative. All voltages are referenced to equipment ground unless otherwise specified.

3. When DE=0V, the supply current specification is valid for the loaded driver.

4. Applicable to peak current. See "Typical Performance Curves" for details.

5. When testing ISL83483, ISL83485, and ISL83491, keep RE=0 to prevent the device from entering SHDN.

6. When testing ISL83483, ISL83485, ISL83491, the high time of the retransmit signal must be short enough (typically <100ns) to prevent the device from entering SHDN.

7. ISL83483, ISL83485, ISL83491 are closed by making RE high and DE low. If the input is in this state for less than 80ns, the part is guaranteed not to enter the shutdown state. If the input is in this state for at least 300 ns, the part is guaranteed to have entered a shutdown state. See the "Low Power Shutdown Mode" section.

8. Keep RE=VCC and set the DE signal low time to be greater than 300ns to ensure the device enters SHDN.

9. Set the retransmission signal high time to greater than 300ns to ensure the device enters SHDN.

application information

RS-485 and RS-422 are differential (balanced) data transmission standard environments for long distance or noisy environments. RS-422 is a subset of RS-485, so RS-485 transceivers are also RS-422 compliant. RS-422 is a point-to-multipoint (multi-drop) standard that allows only one driver and up to 10 (assuming a unit load device) receivers on each bus. RS-485 is a true multidrop standard that allows up to 32 devices (any combination of drivers and receivers) to be loaded in one unit. Allowed for multidrop operation, the RS-485 specification requires that the driver must not support any corruption. Another important advantage of RS-485 is the Common Mode Range (CMR), which specifies that the driver output and receiver input can tolerate signals in the range of +12V to -7V. RS-422 and RS-485 are used for lengths up to 4000' and therefore need to deal with wide CMR ground potential differences, as well as field cables. Receiver Characteristics These devices take advantage of differential input receiver noise immunity and common-mode rejection. Input sensitivity is ±200mV, meeting the required specifications for RS422 and RS-485. The receiver input impedance exceeds 4kΩ and meets the minimum RS-485 "unit load" requirement of 12kΩ. The receiver input function, the common mode voltage can reach +9V/-7V outside the power supply (ie +12V and -7V), making it ideal for long network voltage is a real problem. All receivers include a "fail-on-open" feature that guarantees a high level receiver output unconnected (floating) if the receiver input. The receiver is easy to meet the corresponding. The ISL83483, ISL83485, and ISL83491 receiver outputs are tri-stated with an active low RE input.

Driver function

The RS-485, RS-422 driver is a differential output device that provides at least 1.5V through a 54Ω load (RS-485) and at least 2V into a 100Ω load (RS-422), even if VCC=3V. The drivers feature low propagation delay ramps to maximize bit width and minimize EMI. The drivers for the ISL83483, ISL83485, ISL83491 are three-state via an active high DE input. The slew rate of the ISL83483/88 driver output is limited to minimize EMI, and remove unterminated or improperly terminated nets. The data rate limited versions of these transformations are up to 250kbps. Output ISL83485, ISL83490, ISL83491 drivers are not limited, so faster output transition times allow data rates of at least 10bps. Data Rates, Cables and Terminations RS-485, RS-422 are used for network lengths less than or equal to 4000', but the maximum system data rate increases with transmission length. Devices operating at 10Mbps are limited to a few hundred feet in length, while the 250kbps version can operate over 1000 feet at full data rates and lengths. Twisted pair is the cable network of choice for RS-485 and RS-422. Twisted pair wires are prone to noise and other common-mode electromagnetically induced voltage signals that are differentially effectively rejected by receivers in these integrated circuits. When using 10Mbps, the device must be properly terminated to minimize reflections. Termination is not required to use the 250kbps version, however, termination is recommended unless power consumption is the most important concern. For point-to-point or point-to-multipoint (single driver on bus) networks, the main cable should have a characteristic impedance (usually 120Ω) at its farthest end from the driver. In multi-receiver applications, the stub connecting the receiver to the main cable should be kept as short as possible. Multi-drop (multi-driver) systems require characteristic impedance across the main cable. The cables connecting the transceivers to the mains should be as short as possible.

Built-In Drive Overload Protection As mentioned earlier, the RS-485 specification requires the drive to survive a worst-case bus race. The ISL834XX device meets this requirement with a driver output short-circuit current limit and on-chip thermal shutdown circuitry. The driver output stage contains a short-circuit current limit circuit that ensures that the output current exceeds the RS-485 specification, even at the limit of the common-mode voltage range. In addition, these devices utilize folding circuits that reduce short-circuit current, and therefore, when competing voltages exceed either supply. In the event of a major short circuit, the ISL834XX devices also include a thermal shutdown function when the mold temperature becomes too extreme. This eliminates power consumption, allowing death cooling. The driver drops about 15 degrees in the mold temperature. If the argument persists, the thermal shutdown/reentrant cycle repeats until the fault is resolved. The receiver is in thermal shutdown.

Low Power Shutdown Mode (ISL83483, ISL83485, ISL83491 only) These CMOS transceivers all use a fraction of the power required by their bipolar counterparts, but the ISL83483, ISL83485, ISL83491 include a shutdown function that reduces the already low static ICC to 15nA trickle. When both receiver and driver are disabled simultaneously (RE=VCC and DE=GND) for at least 300 ns. Disabling the driver and less than 80ns receivers guarantees shutdown entry. Note that it is enabled when these devices are turned off. See note 5-9 at the end of the Electrical Specifications table.

Typical performance curve VCC=3.3V, TA=25oC, ISL83483 to ISL83491; unless otherwise specified

Typical Performance Curves VCC=3.3V, TA=25oC, ISL83483 to ISL83491; unless otherwise specified (continued)

Typical Performance Curves VCC=3.3V, TA=25oC, ISL83483 to ISL83491; unless otherwise specified (continued)