전자부품 데이터시트 검색엔진 |
|
ISL32483E 데이터시트(PDF) 10 Page - Intersil Corporation |
|
ISL32483E 데이터시트(HTML) 10 Page - Intersil Corporation |
10 / 17 page ISL32483E, ISL32485E 10 FN7785.0 January 18, 2011 Application Information RS-485 and RS-422 are differential (balanced) data transmission standards used for long haul 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 (multidrop) standard, which allows only one driver and up to 10 (assuming one-unit load devices) receivers on each bus. RS-485 is a true multipoint standard, which allows up to 32 one-unit load devices (any combination of drivers and receivers) on each bus. To allow for multipoint operation, the RS-485 specification requires that drivers must handle bus contention without sustaining any damage. Another important advantage of RS-485 is the extended common mode range (CMR), which specifies that the driver outputs and receiver inputs withstand signals that range from +12V to -7V. RS-422 and RS-485 are intended for runs as long as 4000 feet, so the wide CMR is necessary to handle ground potential differences, as well as voltages induced in the cable by external fields. The ISL3248xE is a family of ruggedized RS-485 transceivers that improves on the RS-485 basic requirements and therefore increases system reliability. The CMR increases to ±25V, while the RS-485 bus pins (receiver inputs and driver outputs) include fault protection against voltages and transients up to ±60V. Additionally, larger-than-required differential output voltages (VOD) increase noise immunity, while the ±16.5kV built-in ESD protection complements the fault protection. Receiver (Rx) Features These devices utilize a differential input receiver for maximum noise immunity and common mode rejection. Input sensitivity is better than ±200mV, as required by the RS-422 and RS-485 specifications. Receiver input (load) current surpasses the RS-422 specification of 3mA and is four times lower than the RS-485 “Unit Load (UL)” requirement of 1mA maximum. Thus, these products are known as “one-quarter UL” transceivers, and there can be up to 128 of these devices on a network while still complying with the RS-485 loading specification. The Rx functions with common mode voltages as great as ±25V, making them ideal for industrial or long networks where induced voltages are a realistic concern. All the receivers include a “full fail-safe” function that guarantees a high-level receiver output if the receiver inputs are unconnected (floating), shorted together, or connected to a terminated bus with all the transmitters disabled (i.e., an idle bus). Rx outputs feature high drive levels (typically 22mA @ VOL =1V) to ease the design of optically coupled isolated interfaces. Except for the ISL32485E, Rx outputs are three-statable via the active low RE input. The Rx includes noise filtering circuitry to reject high-frequency signals, and typically rejects pulses narrower than 50ns (equivalent to 20Mbps). Driver (Tx) Features The RS-485/RS-422 driver is a differential output device that delivers at least 1.5V across a 54Ω load (RS-485) and at least 2.4V across a 100Ω load (RS-422). The drivers feature low propagation delay skew to maximize bit width and to minimize EMI, and all drivers are three-statable via the active high DE input. The driver outputs are slew rate limited to minimize EMI and to minimize reflections in unterminated or improperly terminated networks. High Overvoltage (Fault) Protection Increases Ruggedness The ±60V (referenced to the IC GND) fault protection on the RS-485 pins makes these transceivers some of the most rugged on the market. This level of protection makes the ISL3248xE perfect for applications where power (e.g., 24V and 48V supplies) must be routed in the conduit with the data lines, or for outdoor applications where large transients are likely to occur. When power is routed with the data lines, even a momentary short between the supply and data lines will destroy an unprotected device. The ±60V fault levels of this family are at least five times higher than the levels specified for standard RS-485 ICs. The ISL3248xE protection is active whether the Tx is enabled or disabled, and even if the IC is powered down. If transients or voltages (including overshoots and ringing) greater then ±60V are possible, then additional external protection is required. Widest Common Mode Voltage (CMV) Tolerance Improves Operating Range RS-485 networks operating in industrial complexes or over long distances are susceptible to large CMV variations. Either of these operating environments may suffer from large node-to-node ground potential differences or CMV pickup from external electromagnetic sources, and devices with only the minimum required +12V to -7V CMR may malfunction. The ISL3248xE’s extended ±25V CMR is the widest available, allowing operation in environments that would overwhelm lesser transceivers. Additionally, the Rx will not phase invert (erroneously change state), even with CMVs of ±40V or differential voltages as large as 40V. Cable Invert (Polarity Reversal) Function With large node count RS-485 networks, it is common for some cable data lines to be wired backwards during installation. When this happens, the node is unable to communicate over the network. Once a technician finds the miswired node, he must then rewire the connector, which is time consuming. The ISL32483E and ISL32485E simplify this task by including cable invert pins (INV, DINV, RINV) that allow the technician to invert the polarity of the Rx input and/or the Tx output pins simply by moving a jumper to change the state of the invert pins. When the invert pin is low, the IC operates like any standard RS-485 transceiver, and the bus pins have their normal polarity definition of A and Y being noninverting and B and Z being inverting. With the invert pin high, the corresponding bus pins reverse their polarity, so B and Z are now noninverting, and A and Y become inverting. |
유사한 부품 번호 - ISL32483E |
|
유사한 설명 - ISL32483E |
|
|
링크 URL |
개인정보취급방침 |
ALLDATASHEET.CO.KR |
ALLDATASHEET 가 귀하에 도움이 되셨나요? [ DONATE ] |
Alldatasheet는? | 광고문의 | 운영자에게 연락하기 | 개인정보취급방침 | 링크교환 | 제조사별 검색 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 |