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AD204JY Folha de dados(PDF) 4 Page - Analog Devices |
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AD204JY Folha de dados(HTML) 4 Page - Analog Devices |
4 / 12 page REV. B –4– AD202/AD204 DIFFERENCES BETWEEN THE AD202 AND AD204 The primary distinction between the AD202 and AD204 is in the method by which they are powered: the AD202 operates directly from +15 V dc while the AD204 is powered by a non- isolated externally-supplied clock (AD246) which can drive up to 32 AD204s. The main advantages of using the externally- clocked AD204 over the AD202 are reduced cost in multichannel applications, lower power consumption, and higher bandwidth. In addition, the AD204 can supply substantially more isolated power than the AD202. Of course, in a great many situations, especially where only one or a few isolators are used, the convenience of stand-alone op- eration provided by the AD202 will be more significant than any of the AD204’s advantages. There may also be cases where it is desirable to accommodate either device interchangeably, so the pinouts of the two products have been designed to make that easy to do. MOD RECT & FILTER 3 2 VSIG 1 4 SIGNAL DEMOD ±5V F.S. 25kHz 25kHz POWER OSCILLATOR FB IN– IN+ IN COM 38 37 31 32 POWER RETURN +15V DC VOUT HI LO AD202 +7.5V –7.5V –VISO OUT +VISO OUT ±5V FS 6 5 Figure 1a. AD202 Functional Block Diagram MOD RECT & FILTER 3 2 VSIG 1 4 SIGNAL ±5V F.S. 25kHz 25kHz POWER FB IN– IN+ IN COM 33 32 POWER RETURN (15V p-p/25kHz) VOUT HI LO AD204 +7.5V –7.5V –VISO OUT +VISO OUT ±5V FS 6 5 CLOCK POWER CONV. DEMOD 38 37 Figure 1b. AD204 Functional Block Diagram (Pin Designations Apply to the DIP-Style Package) INSIDE THE AD202 AND AD204 The AD202 and AD204 use an amplitude modulation technique to permit transformer coupling of signals down to dc (Figure 1a and 1b). Both models also contain an uncommitted input op amp and a power transformer which provides isolated power to the op amp, the modulator, and any external load. The power transformer primary is driven by a 25 kHz, 15 V p-p square wave which is generated internally in the case of the AD202, or supplied externally for the AD204. Within the signal swing limits of approximately ±5 V, the output voltage of the isolator is equal to the output voltage of the op amp; that is, the isolation barrier has unity gain. The output sig- nal is not internally buffered, so the user is free to interchange the output leads to get signal inversion. Additionally, in multi- channel applications, the unbuffered outputs can be multiplexed with one buffer following the mux. This technique minimizes offset errors while reducing power consumption and cost. The (Circuit figures shown on this page are for SIP style pack- ages. Refer to page 3 for proper DIP package pinout.) output resistance of the isolator is typically 3 k Ω for the AD204 (7 k Ω for AD202) and varies with signal level and temperature, so it should not be loaded (see Figure 2 for the effects of load upon nonlinearity and gain drift). In many cases a high-imped- ance load will be present or a following circuit such as an output filter can serve as a buffer, so that a separate buffer function will not often be needed. Figure 2. Effects of Output Loading USING THE AD202 AND AD204 Powering the AD202. The AD202 requires only a single +15 V power supply connected as shown in Figure 3a. A bypass ca- pacitor is provided in the module. Figure 3a. Powering the AD204. The AD204 gets its power from an ex- ternally supplied clock signal (a 15 V p-p square wave with a nominal frequency of 25 kHz) as shown in Figure 3b. Figure 3b. AD246 Clock Driver. The AD246 is a compact, inexpensive clock driver that can be used to obtain the required clock from a single 15 V supply. Alternatively, the circuit shown in Figure 4 (essentially an AD246) can be used. In either case, one clock circuit can operate at least 32 AD204s at the rated minimum supply voltage of 14.25 V and one additional isolator can be operated for each 40 mV increase in supply voltage up to 15 V. A supply bypass capacitor is included in the AD246, but if many |
Nº de peça semelhante - AD204JY |
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Descrição semelhante - AD204JY |
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