LTC1411 WUTYPICAL PERFOR A CE CHARACTERISTICSAcquisition Time4096 Points FFT Plot (1MHz)vs Source Resistance 0 100 SINAD = 75dB SFDR = 81dB –20 fSAMPLE = 2.5MHz fIN = 1MHz 10 –40 µs) –60 1 –80 AMPLITUDE (dB) –100 ACQUISITION TIME ( 0.1 –120 –140 0.01 0 250 500 750 1000 1250 1 10 100 1000 10000 100000 FREQUENCY (kHz) SOURCE RESISTANCE (Ω) 1411 G15 1411 G16 UUUPI FU CTIO SA +IN (Pin 1): Positive Analog Input. The ADC converts the AGND (Pins 7 to 9): Analog Ground. AGND1 is the ground difference voltage between A + – IN and AIN with program- for the reference. AGND2 is the ground for the comparator mable input ranges of ±1.8V, ±1.27V, ±0.9V and ±0.64V and AGND3 is the ground for the remaining analog depending on PGA selection. A + IN has common mode circuitry. range between 0V and VDD. AVP (Pin 10): 5V Analog Power Supply. Bypass to AGND A –IN (Pin 2): Negative Analog Input. This pin can be tied with a 10µF tantalum capacitor. to the REFOUT pin of the ADC or tied to an external DC AVM (Pin 11): Analog and Digital Substrate Pin. Tie this voltage. This voltage is also the bipolar zero for the ADC. pin to AGND. A – IN has common mode range between 0V and VDD. D13 to D0 (Pins 12 to 25): Digital Data Outputs. D13 is the REFOUT (Pin 3): 2.5V Reference Output. Bypass to AGND1 MSB (Most Significant Bit). with a 22µF tantalum capacitor if REFOUT is tied to A – IN . No capacitor is needed if the external reference is used to OTR (Pin 26): Out-of-the-Range Pin. This pin can be used drive A – IN . in conjunction with D13 to determine if a signal is less than or greater than the analog input range. If D13 is low and REFIN (Pin 4): Reference Buffer Input. This pin can be OTR is high, the analog input to the ADC exceeds the tied to REFOUT or to an external reference if more maximum voltage of the input range. precision is required. BUSY (Pin 27): Busy Output. Converter status pin. It is REFCOM1 (Pin 5): Noise Reduction Pin. Put a 10µF low during conversion. bypass capacitor at this pin to reduce the noise going into the reference buffer. OGND (Pin 28): Digital Ground for Output Drivers (Data Bits, OTR and BUSY). REFCOM2 (Pin 6): 4.05V Reference Compensation Pin. Bypass to AGND1 with a 10µF tantalum capacitor in OVDD (Pin 29): 3V or 5V Digital Power Supply for Output parallel with a 0.1µF ceramic. Drivers (Data Bits, OTR and BUSY). Bypass to OGND with a 10µF tantalum capacitor. 1411f 6