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ISL32175EIVZ Arkusz danych(PDF) 11 Page - Intersil Corporation |
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ISL32175EIVZ Arkusz danych(HTML) 11 Page - Intersil Corporation |
11 / 22 page 11 FN7529.0 November 19, 2009 Application Information RS-485 and RS-422 are differential (balanced) data transmission standards for use in 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. 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’, so the wide CMR is necessary to handle ground potential differences, as well as voltages induced in the cable by external fields. Receiver Features These devices utilize differential receivers 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 resistance of 48kΩ surpasses the RS-422 specification of 4kΩ and is four times the RS-485 “Unit Load (UL)” requirement of 12kΩ minimum. Thus, these products are known as “one-quarter UL” receivers and there can be up to 128 of these devices on a network while still complying with the RS-485 loading specification. Receiver inputs function with common mode voltages as great as +9V/-7V outside the power supplies (i.e., +12V and -7V with VCC = 3.0V), making them ideal for long networks where induced voltages, and ground potential differences are realistic concerns. All the receivers include a “fail-safe open” function that guarantees a high level receiver output if the receiver inputs are unconnected (floating). All receivers easily support a 20Mbps data rate, and the ISL32173E, ISL32175E, and ISL32177E support data rates up to 80Mbps. All receiver outputs are tri-statable, with the enable scheme varying by part type (see next section). Receiver Enable Functions All product types include functionality to allow disabling of the Rx outputs. The ISL32X73E types feature group (all four Rx) enable functions that are active high (EN) or active low (EN). Receivers enable when EN = 1, or when EN = 0, and they disable only when EN = 0 and EN = 1. ISL32X75E versions use active high paired enable Test Circuits and Waveforms FIGURE 1A. TEST CIRCUIT FIGURE 1B. MEASUREMENT POINTS FIGURE 1. RECEIVER PROPAGATION DELAY FIGURE 2A. TEST CIRCUIT FIGURE 2B. MEASUREMENT POINTS FIGURE 2. RECEIVER ENABLE AND DISABLE TIMES SIGNAL GENERATOR R RO EN A B +1.5V 15pF RO 3V 0V tPLH 1.5V 1.5V VCC OR VL 0V 50% tPHL A 50% 1kΩ VCC GND SW PARAMETER A SW tHZ +1.5V GND tLZ -1.5V VCC tZH (Notes 15, 21) +1.5V GND tZL (Notes 15, 21) -1.5V VCC tZH(SHDN) (Notes 16, 20) +1.5V GND tZL(SHDN) (Notes 16, 20) -1.5V VCC SIGNAL GENERATOR R RO EN A B GND 15pF OR VL RO 3V OR VL 0V 1.5V 1.5V VOH 0V VOH - 0.5V tHZ RO VCC OR VL VOL VOL + 0.5V tLZ EN OUTPUT LOW tZL, tZL(SHDN) tZH, tZH(SHDN) LOWER OF LOWER OF 1.5V OR VL/2 OUTPUT HIGH 1.5V OR VL/2 ISL32173E, ISL32175E, ISL32177E, ISL32273E, ISL32275E, ISL32277E |
Podobny numer części - ISL32175EIVZ |
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Podobny opis - ISL32175EIVZ |
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