Datenblatt-Suchmaschine für elektronische Bauteile |
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ISL5640EVAL Datenblatt(PDF) 9 Page - Intersil Corporation |
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ISL5640EVAL Datenblatt(HTML) 9 Page - Intersil Corporation |
9 / 11 page 3-9 analog sample is taken (see the timing diagram in Figure 1). This time delay is specified as the data latency. After the data latency time, the digital data representing each succeeding analog sample is output during the following clock cycle. The digital output data is provided in offset binary format (see Table 1, A/D Code Table). Internal Reference Voltage Output, VROUT The ISL5640 is equipped with an internal 1.25V bandgap reference voltage generator, therefore, no external reference voltage is required. VROUT should be connected to VRIN when using the internal reference voltage. An external, user- supplied, 0.1 µF capacitor may be connected from the VROUT output pin to filter any stray board noise. Reference Voltage Inputs, I/Q VREFIN The ISL5640 is designed to accept a 1.25V reference voltage source at the VRIN input pins for the I and Q channels. Typical operation of the converter requires VRIN to be set at 1.25V. The ISL5640 is tested with VRIN connected to VROUT yielding a fully differential analog input voltage range of ±0.5V. The user does have the option of supplying an external 1.25V reference voltage. As a result of the high input impedance presented at the VRIN input pin, MΩ typically, the external reference voltage being used is only required to source small amount of reference input current. In order to minimize overall converter noise it is recommended that adequate high frequency decoupling be provided at the reference voltage input pin, VRIN. Analog Input, Differential Connection The analog input of the ISL5640 is a differential input that can be configured in various ways depending on the signal source and the required level of performance. A fully differential connection (Figure 16 and Figure 17) will deliver the best performance from the converter. Since the ISL5640 is powered by a single +3V analog supply, the analog input is limited to be between ground and +3V. For the differential input connection this implies the analog input common mode voltage can range from 0.25V to 2.75V. The performance of the ADC does not change significantly with the value of the analog input common mode voltage. For the AC coupled differential input (Figure 16) and with VRIN connected to VROUT, full scale is achieved when the VIN and -VIN input signals are 0.5VP-P, with -VIN being 180 degrees out of phase with VIN. The converter will be at positive full scale when the I/QIN+ input is at I/QVRIN + 0.25V and the I/QIN- input is at I/QVRIN - 0.25V (I/QIN+ - I/QIN- = +0.5V). Conversely, the converter will be at negative full scale when the I/QIN+ input is equal to I/QVRIN - 0.25V and I/QIN- is at I/QVRIN + 0.25V (I/QIN+ - I/QIN- = -0.5V). The analog input can be DC coupled (Figure 17) as long as the inputs are within the analog input common mode voltage range (0.25V ≤ VDC ≤ 2.75V). The resistors, R, in Figure 17 are not absolutely necessary but may be used as load setting resistors. A capacitor, C, connected from I/QIN+ to I/QIN- will help filter any high frequency noise on the inputs, also improving performance. Values around 20pF are sufficient and can be used on AC coupled inputs as well. Note, however, that the value of capacitor C chosen must take into account the highest frequency component of the analog input signal. Analog Input, Single-Ended Connection The configuration shown in Figure 18 may be used with a single ended AC coupled input. Again, with VRIN connected to VROUT, if VIN is a 1VP-P sinewave, then I/QIN+ is a 1.0VP-P sinewave riding on a positive voltage equal to VDC. The converter will be at positive full scale when I/QIN+ is at VDC + 0.5V (I/QIN+ - I/QIN+ I/QVRIN I/QIN- ISL5640 VIN -VIN R R FIGURE 4. AC COUPLED DIFFERENTIAL INPUT I/QIN+ I/QVRIN I/QIN- ISL5640 VIN -VIN R R C VDC VDC FIGURE 5. DC COUPLED DIFFERENTIAL INPUT I/QIN+ I/QIN- ISL5640 VIN VDC R FIGURE 6. AC COUPLED SINGLE ENDED INPUT ISL5640 |
Ähnliche Teilenummer - ISL5640EVAL |
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Ähnliche Beschreibung - ISL5640EVAL |
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