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TS7001IM8T датащи(PDF) 11 Page - Touchstone Semiconductor Inc |
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TS7001IM8T датащи(HTML) 11 Page - Touchstone Semiconductor Inc |
11 / 20 page TS7001 TS7001DS r1p0 Page 11 RTFDS Typical Application Circuit Figure 4 shows a typical application circuit for the TS7001 where the ADC’s GND pin is connected to the analog ground plane of the system. In this application circuit, the TS7001 has been configured for two-channel operation so the ADC’s VREF is internally connected to VDD; as a result, the analog input range on either analog input is 0V to VDD. It is always considered good engineering practice to bypass the ADC’s VDD with good quality capacitors with short leads (surface-mount components are preferred) and located a very short distance from the ADC. The conversion result at the DOUT pin is a 16- bit word with four leading zeros followed by the MSB of the 12-bit conversion result. In low-power applications, automatic-power-down-at-the-end-of- conversion modes (PM Modes 3 or 4) should be used to improve the ADC’s power consumption- versus-throughput rate performance. For additional information on the TS7001 ’s four power management operating modes, please consult the Operating Modes section of the datasheet. Analog Input Details An equivalent circuit of the analog input structure of the TS7001 is illustrated in Figure 5 where diodes D1 and D2 serve as ESD-clamp protection for the analog inputs. Since there are diodes from the analog input to both VDD and GND, it is important any forward conduction of current in D1 or D2 is avoided. Thus, the analog input signal should never exceed the either VDD or GND by more than 200mV. Even though the maximum current these diodes can conduct without causing irreversible damage to the ADC is 20mA, any small amount of forward diode current into the substrate because of an overvoltage condition on an unselected channel can cause inaccurate conversion results on the selected channel. Attributed to parasitic package pin capacitance, capacitor C1 in Figure 5 is typically about 1 pF. Resistor R1 is the equivalent series resistance of the TS7001 ’s input multiplexer and input sampling switch and is approximately 100 Ω. Capacitor C2 is the ADC sampling capacitor and has a typical capacitance of 10 pF. In signal-acquisition (or ac) applications, the use of an external R-C low-pass filter on either or both analog inputs can be useful in removing out-of-band high-frequency components from the analog input signal. In applications where harmonic distortion and signal-to-noise ratio performance are important, the analog input(s) should be driven from a low- impedance source. Large source impedances will affect significantly the TS7001 ’s ac performance. To lower the driving-point impedance level, it may be necessary to use an input buffer amplifier. The optimal choice for the external drive op amp will be determined by application requirements as well as the TS7001 ’s dynamic performance. When the analog input is not driven by an external amplifier, the driving-point source impedance should be low. The maximum source impedance will depend upon the amount of total harmonic distortion (THD) that can be tolerated in the application. THD will increase as the source impedance increases Figure 4: TS7001's Typical Application Circuit. Figure 5: TS7001’s Analog Input Equivalent Circuit. INPUT FREQUENCY - kHz VDD = 3V 3V Ext VREF -65 -75 -85 -90 0.2 10 50 90 40 -60 Figure 6: TS7001 THD vs Analog Input Frequency RIN = 50 Ω, CIN = 2.2nF RIN = 10 Ω, CIN = 10nF -70 -80 80 20 30 60 70 |
Аналогичный номер детали - TS7001IM8T |
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Аналогичное описание - TS7001IM8T |
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