поискавой системы для электроныых деталей |
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ISL54063IRTZ-T датащи(PDF) 10 Page - Intersil Corporation |
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ISL54063IRTZ-T датащи(HTML) 10 Page - Intersil Corporation |
10 / 15 page 10 FN6582.0 February 25, 2009 This method is not acceptable for the signal path inputs. Adding a series resistor to the switch input defeats the purpose of using a low rON switch. Alternatively, connecting external Schottky diodes from the V+ rail to the signal pins will shunt the fault current through the Schottky diode instead of through the internal ESD diodes, thereby protecting the switch. These Schottky diodes must be sized to handle the expected fault current.. Power-Supply Considerations The ISL54063 and ISL54064 construction is typical of most single supply CMOS analog switches which have two supply pins: V+ and GND. V+ and GND provide the CMOS switch bias and sets their analog voltage limits. Unlike switches with a 5.5V maximum supply voltage, the ISL54063 and ISL54064 have a 6.5V maximum supply voltage providing plenty of head room for the 10% tolerance of 5.5V supplies due to overshoot and noise spikes. The minimum recommended supply voltage is 1.8V. It is important to note that the input signal range, switching times, and ON-resistance degrade at lower supply voltages. Refer to the “Electrical Specifications” tables, beginning on page 4, and “Typical Performance Curves”, beginning on page 11, for details. V+ and GND also power the internal logic and level shifters. The level shifters convert the input logic levels to V+ and GND signals levels to drive the analog switch gate terminals. A high frequency decoupling capacitor placed as close to the V+ and GND pin as possible is recommended for proper operation of the switch. A value of 0.1µF is highly recommended. Negative Signal Capability The ISL54063 and ISL54064 contains circuitry that allows the analog input signal to swing below ground. The device has an analog signal range of 6.5V below V+ up to the V+ rail (see Figure 14) while maintaining low rON performance. For example, if V+ = 5V, then the analog input signal range is from -1.5V to +5V. If V+ = 2.7V then the range is from -3.8V to +2.7V. Logic-Level Thresholds This switch family is 1.8V CMOS compatible (0.45V VOLMAX and 1.35V VOHMIN) over a supply range of 1.8V to 3.3V (see Figure 16). At 3.3V the VIL level is 0.5V maximum. This is still below the 1.8V CMOS guaranteed low output maximum level of 0.45V, but noise margin is reduced. At 3.3V the VIH level is 1.4V minimum. While this is above the 1.8V CMOS guaranteed high output minimum of 1.35V under most operating conditions the switch will recognize this as a valid logic high. The digital input stages draw supply current whenever the digital input voltage is not at one of the supply rails. Driving the digital input signals from GND to V+ with a fast transition time minimizes power dissipation. The ISL54063 and ISL54064 have been designed to minimize the supply current whenever the digital input voltage is not driven to the supply rails (0V to V+). For example driving the device with 2.85V logic high while operating with a 4.2V supply the device draws only 1µA of current. High-Frequency Performance In 50 Ω systems, the ISL54063 and ISL54064 have an ON switch -3dB bandwidth of 60MHz (see Figure 19). The frequency response is very consistent over a wide V+ range, and for varying analog signal levels. An OFF switch acts like a capacitor across the open terminals and AC couples higher frequencies, resulting in signal feed-through from a switch’s input to its output. Off-Isolation is the resistance to this feed-through. Crosstalk indicates the amount of feed-through from one switch channel to another switch channel. Figure 20 details the high Off-Isolation and Crosstalk rejection provided by this part. At 100kHz, Off-Isolation is about 60dB in 50 Ω systems, decreasing approximately 20dB per decade as frequency increases. At 1MHz, Crosstalk is about -75dB in 50 Ω systems, decreasing approximately 20dB per decade as frequency increases. Leakage Considerations Reverse ESD protection diodes are internally connected between each analog-signal pin, V+ and GND. One of these diodes conducts if any analog signal exceeds the recommended analog signal range. Virtually all the analog switch leakage current comes from the ESD diodes and reversed biased junctions in the switch cell. Although the ESD diodes on a given signal pin are identical and therefore fairly well balanced, they are reverse biased differently. Each is biased to either the +Ring or -Ring and the analog input signal. This means their leakages will vary as the signal varies. The difference in the two diode leakages to the +Ring or -Ring and the reverse biased junctions at the internal switch cell constitutes the analog-signal-path leakage current. GND VCOMx VNCx V+ LOGIC INPUTS VNOx -RING +RING CLAMP 1k Ω OR FIGURE 8. OVERVOLTAGE PROTECTION ISL54063, ISL54064 |
Аналогичный номер детали - ISL54063IRTZ-T |
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Аналогичное описание - ISL54063IRTZ-T |
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