LTC1606 UUWUAPPLICATIO S I FOR ATIO changing between 1111 1111 1111 1111 and 0000 0000 If the external resistors are not used, the resulting offset 0000 0000. The gain error is trimmed by adjusting resistor and gain error ranges are shown in Table 1. R4. An input voltage of 9.999542V (+FS – 1.5LSB) is applied to V DC Performance IN and R4 is adjusted until the output code is changing between 0111 1111 1111 1110 and 0111 1111 One way of measuring the transition noise associated with 1111 1111. Figure 6 shows the bipolar transfer character- a high resolution ADC is to use a technique where a DC istic of the LTC1606. signal is applied to the input of the ADC and the resulting output codes are collected over a large number of conver- sions. For example in Figure 7, the distribution of output 1 ±10V INPUT VIN 2 code is shown for a DC input that has been digitized 4096 200Ω AGND1 1% times. The distribution is Gaussian and the RMS code + 2.2µF transition is about 0.65LSB. 3 33.2k REF 1% 5V LTC1606 100k 392k R4 DIGITAL INTERFACE 50k 4 + CAP R3 10µF 50k Internal Clock 5 AGND2 1606 • F05 The ADC has an internal clock that is trimmed to achieve a typical conversion time of 2.3µs. No external adjust- Figure 5. ± 10V Input with Offset and Gain Trim ments are required and, with the typical acquisition time of 1µs, throughput performance of 250ksps is assured. 2500 011...111 011...110 BIPOLAR 2000 ZERO 000...001 1500 000...000 111...111 COUNTS 1000 OUTPUT CODE 111...110 500 100...001 FS = 20V 100...000 1LSB = FS/65536 0 –1 0V 1 –3 –2 –1 0 1 2 3 4 –FS/2 FS/2 – 1LSB LSB LSB CODE 1606 • F07 INPUT VOLTAGE (V) 1606 • F06 Figure 6. LTC1606 Bipolar Transfer CharacteristicsFigure 7. Histogram for 4096 ConversionsTable 1WITH BOTH EXTERNALWITHOUT THE EXTERNALWITHOUT EITHER EXTERNALERROR TERMRESISTORS INCLUDED33.2k RESISTORRESISTOR INCLUDED Offset Error – 10mV < Error < 10mV 10mV < Error< 55mV 54mV < Error < 155mV + Full-Scale Error – 0.25% < Error < 0.25% – 0.50% < Error < 0.50% – 1.3% < Error < –0.10% – 3.40% < Error < –0.85% – Full-Scale Error – 0.25% < Error < 0.25% – 0.50% < Error < 0.50% 0.25% < Error < 1.40% 2.10% < Error < 6.15% 1606fa 10