The ISL315xE is protected by IEC61000 ESD, and 5V meets the standard for balanced communication of electrical transceivers for RS-485 and RS-422. Driver outputs and receiver inputs are protected from ±16.5kV ESD strikes without latch-up. Transmitters in this series offer excellent differential output voltage (2.4V min), input required RS-48554Ω loads, improve noise immunity, or allow eight 120Ω terminations in a "star" topology. The bus current of these devices is very low, thus providing a true "1/8 unit load" to the RS-485 bus. This allows up to 256 transceivers on the network to use repeaters. The receiver (Rx) input has a "completely fail-safe" design if the Rx input is floating, shorted, or on a terminated but undriven bus. The Rx output has a high drive level - typically 28mA @VOL=1V (simplified optocoupler isolation design interface). Half-duplex (Rx input and Tx output multiplexed and full-duplex pins are available. See page 2 for key functions and configuration device numbers in Table 1.

feature

High drive video on demand. 2.4V (min) at RD=54Ω for better noise immunity, or drive up to 8 terminations

±16.5kV IEC61000 ESD protection on I/O bus pins

High transient overvoltage tolerance. ? 00 volts

Fully Fail-Safe (Open, Short, Terminated) Receivers

High Rx IOL for stand-alone designed optocouplers

Hot Swap Circuitry - Tx and Rx outputs remain unchanged Three states on power up/down

Actual 1/8 unit load for up to 256 devices on the bus

high data rate. up to 20Mbps

Low quiescent supply current. 600 microamps

Ultra-low shutdown supply current. 70 nanometers

application

Utility meter/automatic meter reading system

High Node Count Systems

PROFIBUS® and fieldbus networks, and factory automation

security camera network

Architectural Lighting and Environmental Control Systems

Industrial/Process Control Networks

1. Add "-T" suffix for tapes and reels. See TB347 for reel specifications.

2. Lead-free PDIPs can only be used for through-hole wave solder processing. They are not intended for reflow soldering applications.

3. These Intersil lead-free plastic packaged products feature a special lead-free material kit, molding compound/mold accessory material and 100% matte tinplate plus annealed (e3 termination finish, RoHS compliant and compatible with both SnPb and no lead soldering operations). Intersil lead-free products are classified as MSL meeting or exceeding the lead-free requirements of IPC/JEDEC J STD-020 at lead-free peak reflow temperatures.

4. For Moisture Sensitivity Level (MSL), see the device information pages for ISL3150E, ISL3152E, ISL3153E, ISL3155E, ISL3156E and ISL3158E. See techbrief TB363 for more information on MSL.

Absolute Maximum Ratings Thermal Information

VCC is grounded. 7V input voltage DI, DE, RE. -0.3V to (VCC+0.3V)

Input/output voltage A/Y, B/Z, A, B, Y, Z. -9V to +13VA/Y, B/Z, A, B, Y, Z (transient pulse through 100Ω, Note 16). 00 volts. -0.3V to (VCC+0.3V) Short Circuit Duration Y, Z. Continuous electrostatic discharge rating. see spec sheet

Recommended Operating Conditions

voltage. 5 volts

temperature range. -40°C to +85°C

Bus pin common mode voltage range. -7V to +12V

Thermal Resistance (Typical, Note 5) θJA (Celsius/Watt)

8Ld SOIC. 105

8 Ld MSOP, PDIP*. 140

10ld maximum continuous working pressure. 130

14Ld SOIC. 130

Maximum connection temperature (plastic packaging). +150 degrees Celsius

Maximum storage temperature range. -65°C to +150°C

Lead-free reflow profile. See the link below

/pbfree/Pb-FreeReflow.asp

*Pb-free PDIPs are available for through-hole wave solder processing only. They are not intended for reflow solder processing applications.

NOTE: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely affect product reliability, resulting in failures not covered under warranty.

Note:

5. θJA is measured with components mounted on a high-efficiency thermal conductivity test board in free air. See Technical Brief for details on TB379.

Electrical specification test conditions: VCC=4.5V～5.5V; unless otherwise specified. Typical values are VCC=5V, TA=+25°C (Note 6). Blackbody limits apply over the operating temperature range,

-40°C to +85°C.

Electrical specification test conditions: VCC=4.5V～5.5V; unless otherwise specified. Typical values are VCC=5V, TA=+25°C (Note 6). Blackbody limits apply to operating temperature range, -40°C to +85°C (continued)

notes:

6. All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to equipment ground unless otherwise specified.

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

8. Applicable to peak current. See "Typical Performance Curves" at the beginning of page 14 for more information.

9. Keep RE=0 to prevent the device from entering SHDN.

10. The retransmit high time must be short enough (typically <100ns) to prevent the device from entering SHDN.

11. Turn off the transceiver by driving RE high and DE low. If the input is in this state for less than 60ns, it is guaranteed not to enter a shutdown state. If the input is in this state for at least 600 ns, the part is guaranteed to have gone off. See "Low Power Shutdown Mode" on page 13.

12. Keep RE=VCC and set DE signal low time to >600ns to ensure the device goes to SHDN.

13. Set the retransmission signal high time to greater than 600ns to ensure that the device enters SHDN.

14. Unless otherwise specified, parameters with minimum and/or maximum limits are 100% tested at +25°C. Set temperature limits are characterized and not production tested.

15. See Figure 8 for more information and performance over temperature.

16. Tested per TIA/EIA-485-A Section 4.2.6 (±100V for 15 microseconds at 1% duty cycle).

17. Limits determined by characterization, no production testing.

application information

RS-485 and RS-422 are standard environments for differential (balanced) data transmission over long distances or noise. 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, allowing up to 32 devices (any combination of drivers and receivers) on a unit load per bus. In order to allow multidrop operation, the RS-485 specification requires that the driver must handle the arguing that there is no loss of the bus. Another important advantage of RS-485 is the common mode range (CMR), which specifies that the driver output and receiver input can tolerate a range from +12V to -7V. RS-422 and RS-485 are suitable for operation up to 4000', so wide CMRs are also required to handle ground potential differences due to voltages induced in cables by external electric fields. Receiver (Rx) Function These devices utilize differential input receivers for maximum noise immunity and common mode rejection. Input sensitivity is better than ±200mV and complies with RS-422 and RS-485 specifications. The Rx output has a high drive level (typically 28mA@VOL=1V) to simplify the design of the optically coupled isolated interface. The receiver input resistance of 96kΩ exceeds the RS-422 specification of 4kΩ, which is 8 times the load (UL) requirement for RS-485" units" minimum 12kΩ. Therefore, these products are referred to as "one-eighth UL" transceivers, and there can be up to 256 of these devices on a network while still complying with the RS-485 loading specification.

The Rx inputs function as large as the common mode voltage is ±7V outside the power supply (ie +12V and -7V), making them ideal for long net voltages is a real problem. All receivers include a "complete fail-safe" feature if the receiver inputs are not connected (floating), shorted together, or disabled with all transmitters connected to the terminal bus. The receivers easily satisfy the corresponding drivers, and all receiver outputs are three statables via the active low RE input. Driver (Tx) Function The RS-485/RS-422 driver is a differential output device that provides at least 2.4V through a 54Ω load (RS-485) and at least 2.8V into a 100Ω load (RS-422). This driver features a low propagation delay ramp to maximize bit width and minimize EMI, all three statables via activated high DE inputs. The 115kbps and 1Mbps driver outputs are slew rate limited to minimize EMI and minimize reflections for unterminated or improperly terminated networks. The outputs of the ISL3156E and ISL3158E drivers are not limited, so faster output transition times allow for data rates of at least 20Mbps. High VOD improves noise immunity and flexibility The ISL315xE driver design provides greater differential output voltage (VOD) than the RS-485 standard requires, or more than most RS-485 transmitters can provide. A minimum ±2.4V VOD is guaranteed to be at least ±900mV with higher noise immunity than networks built using standard 1.5V VOD transmitters. Another advantage of large VODs is the ability to drive more than two bus terminations, allowing in "star" and other multi-terminal, "non-standard" network topologies. Figure 8, which details the VOD and IOUT characteristics of the transmitter, including six (20Ω) and eight (15Ω) 120Ω terminations. The diagram shows that the driver typically converts 1.65/1.5V to 6/8 even at a worst-case temperature of +85°C. The RS-485 standard requires a minimum of 1.5V VOD divided into two terminations, but the ISL315xE provides RS-485 voltage levels in quantities of terminations.

Hot Swap Capability When a device is powered up, there is a time when the processor or ASIC driving the RS-485 timing control lines (DE, RE) cannot ensure that the RS-485 Tx and Rx outputs remain disabled. If a device is connected to the bus, driver activation initiated too early during power-up may crash the bus. To avoid this situation, the ISL315xE devices include a "hot swap" feature. Circuit monitors VCC to ensure that Tx and Rx outputs remain disabled during power-up and power-down regardless of the state of DE If VCC is less than ~3.4V, the processor/ASIC has a chance to stabilize and drive the RS-485 control lines in the correct state .

ESD Protection All pins on these devices include a Level 3 (>7kV) Human Body Model (HBM) ESD protection structure, but the RS-485 pins (driver output and receiver input) contain advanced structures during ESD events exceeding ±16.5kV Medium surviving HBM and ±16.5kV (1/2 duplex) IEC61000-4-2. The RS-485 pins are particularly vulnerable to ESD attacks because they are usually connected to the finished look. Simply touching port pins or connecting cables can cause ESD events that can destroy unprotected ICs. These new ESD structures protect devices that are powered up and have a common-mode range of -7V to +12V without degrading RS-485 performance. This built-in ESD protection eliminates the need for board-level protection structures (such as TVS diodes), and the associated, undesired capacitive loading of them. IEC61000-4-2 Testing The IEC61000 test method applies to finished devices, not individual integrated circuits. Therefore, the pins most likely to be exposed to an ESD event are those exposed to the outside world (in this and tested configurations (power up) in a typical application) rather than testing each pin combination. The IEC61000 standard is lower with large charge coupled The current limiting resistor storage capacitor produces a much more severe test than the HBM test. Additional ESD protection built into the device's RS-485 pins allows the device to be designed to meet Class 4 standards without the need for additional board-level protection on the RS-485 port.

Air-gap discharge test method For this test method, the live probe tip is directed toward the IC pin until the voltage arcs with it. The waveform of the current sent to the IC pins depends on the proximity speed, humidity, temperature, etc., so repeatable results are obtained. The ISL315xE 1/2-duplex RS-485 pins can withstand air gap discharges of ±16.5kV. Contact Discharge Test Method During a contact discharge test, the probe contacts the pins before the probe tip is energized, thus eliminating air gap related variables. The result is a more repeatable and predictable test, but device limitations prevent devices from testing voltages higher than ±9kV. The RS-485 pins of all ISL315xE versions can withstand touch voltage discharges of ±9kV. Data Rates, Cables, and Terminations RS-485/RS-422 are used for network lengths up to 4000', but the maximum system data rate increases with transmission length. Devices operating at 20Mbps are limited to lengths less than 100', while the 115kbps version can operate at lengths up to 1000 feet. Twisted pair is the cable network of choice for RS-485/RS-422. Twisted-pair cables are prone to noise other common electromagnetically induced voltage-mode signals that are effectively used by differential receivers in these integrated circuits. When using 20Mbps, the device must be properly terminated to minimize reflections. Termination is not required for short networks using the 115kbps version, however, termination is recommended unless power loss is an overriding concern. For point-to-point or point-to-multipoint (single driver open bus) networks, the main cable should have a characteristic impedance (usually 120Ω) at the end furthest away from the driver. In multi-receiver applications, the stubs connecting the receivers to the main cable should be kept as short as possible. Multi-drop (multi-driver) systems require that the main cable be terminated with characteristic impedance at both ends. Stubs connecting the transceivers to the main cable should be kept as short as possible.

Built-in driver overload protection As mentioned earlier, the RS-485 specification requires drivers to survive the worst bus conflicts intact. These devices output short-circuit current limit and on-chip thermal shutdown circuitry through the driver. The driver output stage contains a short-circuit current limit circuit that ensures that the output current never exceeds the RS-485 specification, even at the common-mode voltage range limit. In the event of a major short circuit, the device also includes a thermal shutdown feature that can be disabled when the mold temperature reaches too far. This eliminates power consumption, allowing death cooling. The driver automatically re-enabled after the mold temperature dropped by about 15°C. If persistent, the thermal shutdown/re-enable cycle repeats until the fault is resolved. The receiver remains operational during thermal shutdown. Low Power Shutdown Mode These CMOS transceivers use a fraction of the power their bipolar partners require, but they also include a shutdown feature that reduces the already low quiescent ICC into a trickle of 70nA. These devices enter whenever the receiver and driver are simultaneously disabled (RE=VCC and DE=GND) for at least 600 ns. Disabling both drivers for receivers less than 60ns ensures that the transceiver does not go into shutdown. Note that the transceiver is enabled from shutdown. Refer to Notes 9, 10, 11, 12 and 13 in the "Specifications" table on page 9 at the end of "Electrical" for more information

Typical Performance Curves VCC=5V, TA=+25°C; unless otherwise specified.

Typical Performance Curves VCC=5V, TA=+25°C; unless otherwise specified. (continued)