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ADM3485EAR データシート(PDF) 8 Page - Analog Devices |
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ADM3485EAR データシート(HTML) 8 Page - Analog Devices |
8 / 11 page ADM3485E –8– REV. A Table I. Comparison of RS-422 and RS-485 Interface Standards Specification RS-422 RS-485 Transmission Type Differential Differential Maximum Data Rate 10 MB/s 10 MB/s Maximum Cable Length 4000 ft. 4000 ft. Minimum Driver Output Voltage ±2 V ±1.5 V Driver Load Impedance 100 Ω 54 Ω Receiver Input Resistance 4 k Ω min 12 k Ω min Receiver Input Sensitivity ±200 mV ±200 mV Receiver Input Voltage Range –7 V to +7 V –7 V to +12 V No. of Drivers/Receivers Per Line 1/10 32/32 Table II. Transmitting Truth Table Transmitting Inputs Outputs RE DE DI B A X1 1 0 1 X1 0 1 0 0 0 X Hi-Z Hi-Z 1 0 X Hi-Z Hi-Z Table III. Receiving Truth Table Receiving Inputs Outputs RE DE A–B RO 0 X > +0.2 V 1 0 X < –0.2 V 0 0 X Inputs O/C 1 1X X Hi-Z ESD/EFT TRANSIENT PROTECTION SCHEME The ADM3485E uses protective clamping structures on its inputs and outputs that clamp the voltage to a safe level and dissipate the energy present in ESD (Electrostatic) and EFT (Electrical Fast Transients) discharges. The protection structure achieves ESD protection up to ±8 kV according to IEC1000-4-2, and EFT protection up to ±2 kV on all I-O lines. ESD TESTING Two coupling methods are used for ESD testing, contact dis- charge and air-gap discharge. Contact discharge calls for a di- rect connection to the unit being tested. Air-gap discharge uses a higher test voltage but does not make direct contact with the unit under test. With air discharge, the discharge gun is moved toward the unit under test, developing an arc across the air gap, hence the term air-discharge. This method is influenced by hu- midity, temperature, barometric pressure, distance and rate of closure of the discharge gun. The contact-discharge method, while less realistic, is more repeatable and is gaining acceptance and preference over the air-gap method. Although very little energy is contained within an ESD pulse, the extremely fast rise time, coupled with high voltages, can cause failures in unprotected semiconductors. Catastrophic destruction can occur immediately as a result of arcing or heat- ing. Even if catastrophic failure does not occur immediately, the device may suffer from parametric degradation, which may result in degraded performance. The cumulative effects of con- tinuous exposure can eventually lead to complete failure. I-O lines are particularly vulnerable to ESD damage. Simply touching or plugging in an I-O cable can result in a static dis- charge that can damage or completely destroy the interface product connected to the I-O port. It is extremely important, therefore, to have high levels of ESD protection on the I-O lines. It is possible that the ESD discharge could induce latchup in the device under test, so it is important that ESD testing on the I-O pins be carried out while device power is applied. This type of testing is more representative of a real-world I-O discharge where the equipment is operating normally when the discharge occurs. TEMPERATURE – C 1.20 –50 70 –30 –10 10 30 50 1.15 1.05 1.00 0.95 0.80 1.10 0.90 0.85 90 110 0.75 0.70 ICC (mA) RE = LO, DE = LO ICC (mA) DE = VCC, RE = X Figure 19. Supply Current vs. Temperature TEMPERATURE – C 100 –40 80 –20 0 204060 90 70 60 50 20 80 40 30 10 0 ICC (mA) Figure 20. Shutdown Current vs. Temperature |
同様の部品番号 - ADM3485EAR |
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同様の説明 - ADM3485EAR |
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