 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ISL8487E Datasheet(PDF) 9 Page - Intersil Corporation |
|
||||||||||||||||||||||||||||||
ISL8487E Datasheet(HTML) 9 Page - Intersil Corporation |
|
|
9 / 14 page  9 FN6051.6 All the receivers include a “fail-safe if open” function that guarantees a high level receiver output if the receiver inputs are unconnected (floating). Receivers easily meet the data rates supported by the corresponding driver, and receiver outputs are three-statable via the active low RE input. Driver Features The RS-485/422 driver is a differential output device that delivers at least 1.5V across a 54 Ω load (RS-485), and at least 2V across a 100 Ω load (RS-422). The drivers feature low propagation delay skew to maximize bit width, and to minimize EMI. Driver outputs are three-statable via the active high DE input. The ISL8487E and ISL81487L driver outputs are slew rate limited to minimize EMI, and to minimize reflections in unterminated or improperly terminated networks. Data rate on these slew rate limited versions is a maximum of 250kbps. ISL81487E drivers are not limited, so faster output transition times allow data rates of at least 5Mbps. Data Rate, Cables, and Terminations RS-485/422 are intended for network lengths up to 4000’, but the maximum system data rate decreases as the transmission length increases. Devices operating at 5Mbps are limited to lengths less than a few hundred feet, while the 250kbps versions can operate at full data rates with lengths in excess of 1000’. Twisted pair is the cable of choice for RS-485/422 networks. Twisted pair cables tend to pick up noise and other electromagnetically induced voltages as common mode signals, which are effectively rejected by the differential receivers in these ICs. To minimize reflections, proper termination is imperative when using the 5Mbps device. Short networks using the 250kbps versions need not be terminated, but, terminations are recommended unless power dissipation is an overriding concern. In point-to-point, or point-to-multipoint (single driver on bus) networks, the main cable should be terminated in its characteristic impedance (typically 120 Ω) at the end farthest from the driver. In multi-receiver applications, stubs connecting receivers to the main cable should be kept as short as possible. Multipoint (multi-driver) systems require that the main cable be terminated in its characteristic impedance at both ends. Stubs connecting a transceiver to the main cable should be kept as short as possible. Built-In Driver Overload Protection As stated previously, the RS-485 spec requires that drivers survive worst case bus contentions undamaged. These devices meet this requirement via driver output short circuit current limits, and on-chip thermal shutdown circuitry. The driver output stages incorporate short circuit current limiting circuitry which ensures that the output current never exceeds the RS-485 spec, even at the common mode voltage range extremes. Additionally, these devices utilize a foldback circuit which reduces the short circuit current, and thus the power dissipation, whenever the contending voltage exceeds either supply. In the event of a major short circuit condition, these devices also include a thermal shutdown feature that disables the drivers whenever the die temperature becomes excessive. This eliminates the power dissipation, allowing the die to cool. The drivers automatically re-enable after the die temperature drops about 15 degrees. If the contention persists, the thermal shutdown/re-enable cycle repeats until the fault is cleared. Receivers stay operational during thermal shutdown. Low Power Shutdown Mode (Excluding ISL81487E) These CMOS transceivers all use a fraction of the power required by their bipolar counterparts, but the ISL8487E and ISL81487L include a shutdown feature that reduces the already low quiescent ICC to a 500nA trickle. They enter shutdown whenever the receiver and driver are simultaneously disabled (RE =VCC and DE = GND) for a period of at least 600ns. Disabling both the driver and the receiver for less than 50ns guarantees that shutdown is not entered. Note that receiver and driver enable times increase when enabling from shutdown. Refer to Notes 5-9, at the end of the Electrical Specification table, for more information. ESD Protection All pins on these interface devices include class 3 Human Body Model (HBM) ESD protection structures, but the RS-485 pins (driver outputs and receiver inputs) incorporate advanced structures allowing them to survive ESD events in excess of ±15kV HBM. The RS-485 pins are particularly vulnerable to ESD damage because they typically connect to an exposed port on the exterior of the finished product. Simply touching the port pins, or connecting a cable, can cause an ESD event that might destroy unprotected ICs. These new ESD structures protect the device whether or not it is powered up, protect without allowing any latchup mechanism to activate, and without degrading the RS-485 common mode range of -7V to +12V. This built-in ESD protection eliminates the need for board level protection structures (e.g., transient suppression diodes), and the associated, undesirable capacitive load they present. ISL8487E, ISL81487L, ISL81487E |
Similar Part No. - ISL8487E |
|
Similar Description - ISL8487E |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
allmanual.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
