LTC2412 Linear Technology, LTC2412 Datasheet

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... ID included in the conversion results. It uses delta-sigma technology and provides single conversion settling of the digital filter. Through a single pin, the LTC2412 can be configured for better than 110dB input differential mode rejection at 50Hz or 60Hz 2 can be driven by an external oscillator for a user defined rejection frequency ...

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... GND .................................... – 0. Digital Input Voltage to GND ........ – 0. Digital Output Voltage to GND ..... – 0. Operating Temperature Range LTC2412C ............................................... LTC2412I ............................................ – Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T ...

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... C. (Note 3) A CONDITIONS + Voltage – Voltage + Voltage – Voltage + 5.5V GND CC – 5.5V 5. 5.5V, REF = 5.5V CC – 5.5V, REF = GND CC LTC2412 MIN TYP MAX UNITS 130 140 dB 140 dB 140 dB 110 140 dB 110 140 dB 130 140 dB 120 dB 120 dB 120 dB MIN TYP MAX UNITS GND – ...

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... LTC2412 U U DIGITAL I PUTS A D DIGITAL OUTPUTS operating temperature range, otherwise specifications are at T SYMBOL PARAMETER V High Level Input Voltage IH CS Low Level Input Voltage IL CS High Level Input Voltage IH SCK V Low Level Input Voltage IL SCK I Digital Input Current ...

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... Note 11: The external oscillator is connected to the F oscillator frequency, f Note 12: The converter uses the internal oscillator Note 13: The output noise includes the contribution of the internal calibration operations. = 153600Hz 2% Note 14: Guaranteed by design and test correlation. LTC2412 MIN TYP MAX 2.56 2000 0.25 390 0.25 390 130 ...

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... LTC2412 W U TYPICAL PERFOR A CE CHARACTERISTICS Total Unadjusted Error vs Temperature ( 5V) REF 1.5 1.0 0 –0.5 + REF = – REF = GND T = – REF A –1 2.5V INCM F = GND O –1.5 –2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 2 2.5 V (V) IN 2412 G01 ...

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... REF = 2.5V REF – REF = GND –0 GND O –1 TIME (HOURS) 2412 G17 LTC2412 Noise Histogram (Output Rate = 52.5Hz 5V 2.5V) CC REF 12 10,000 CONSECUTIVE GAUSSIAN READINGS DISTRIBUTION 3.852ppm 2.5V = 0.326ppm REF ...

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... LTC2412 W U TYPICAL PERFOR A CE CHARACTERISTICS RMS Noise vs V INCM 850 825 800 775 750 + REF = 5V – REF = GND 725 REF + INCM – 700 INCM 675 F = GND 650 –0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 V (V) INCM ...

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... IN = GND – GND –60 –80 –100 –120 –140 120 150 180 210 240 FREQUENCY AT V (Hz) CC 2412 G35 LTC2412 – Full-Scale Error vs Temperature ( REF = 5V – REF = GND GND – 2. GND O 0 –1 – ...

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... LTC2412 W U TYPICAL PERFOR A CE CHARACTERISTICS Conversion Current vs Temperature 240 V = 5.5V 230 CC 220 210 F = GND GND 200 SCK = NC SDO = NC 190 180 170 V = 2.7V CC 160 –45 –30 – TEMPERATURE ( C) 2412 G37 CTIO S V (Pin 1): Positive Supply Voltage. Bypass to GND with tantalum capacitor in parallel with 0 ...

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... O W AUTOCALIBRATION AND CONTROL + DIFFERENTIAL 3RD ORDER – MODULATOR + – DECIMATING FIR CH0/CH1 Figure 1. Functional Block Diagram C = 20pF LOAD 2412 TA03 LTC2412 = OV), the converter uses its internal oscillator EOSC INTERNAL OSCILLATOR F O (INT/EXT) SCK SERIAL SDO INTERFACE CS PING-PONG 2412 1.69k ...

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... Clocked by the on-chip oscillator, the LTC2412 achieves a minimum of 110dB rejection at the line fre- quency (50Hz or 60Hz 2%). Ease of Use The LTC2412 data output has no latency, filter settling delay or redundant data associated with the conversion cycle. There is a one-to-one correspondence between the 2412 F02 conversion and the output data ...

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... Output Data Format – pin. The LTC2412 serial output data stream is 32 bits long. The first 3 bits represent status information indicating the conversion state, selected channel and sign. The next 24 bits are the conversion result, MSB first. The remaining 5 ...

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... If both Bit 29 and Bit 28 are HIGH, the differential input voltage is above +FS. If both Bit 29 and Bit 28 are LOW, the differential input voltage is below –FS. The function of these bits is summarized in Table 1. Table 1. LTC2412 Status Bits Bit 31 Input Range EOC V 0.5 • ...

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... When a fundamental rejection frequency different from 50Hz or 60Hz is required or when the converter must be synchronized with an outside source, the LTC2412 can operate with an external conversion clock. The converter automatically detects the presence of an external clock signal at the F pin and turns off the internal oscillator ...

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... SDO pin on the falling edge of the serial clock. In the Internal SCK mode of operation, the SCK pin is an output and the LTC2412 creates its own serial clock by dividing the internal conversion clock the External SCK mode of operation, the SCK pin is used as input. The ...

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... Grounding CS will force the ADC to continuously convert at the maximum output rate selected by F SERIAL INTERFACE TIMING MODES The LTC2412’s 3-wire interface is SPI and MICROWIRE compatible. This interface offers several flexible modes of operation. These include internal/external serial clock 3-wire I/O, single cycle conversion and autostart. The Table 4 ...

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... Figure 7. CS may be permanently tied to ground, simplifying the user interface or isolation barrier. The external serial clock mode is selected at the end of the power-on reset (POR) cycle. The POR cycle is concluded 2. LTC2412 2 + REFERENCE REF VOLTAGE 3 13 – 0. REF SCK CC ...

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... CS (if EOC = LOW ( LOW during the falling edge of EOC). The value of t EOCtest oscillator (F external oscillator of frequency f 3.6 pulled HIGH before time t EOSC LTC2412 50Hz REJECTION = EXTERNAL OSCILLATOR = 60Hz REJECTION 2-WIRE INTERFACE 8, 9, 10, 15, 16 ...

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... SCK pin or by never pulling CS HIGH when SCK is LOW. Whenever SCK is LOW, the LTC2412’s internal pull-up at pin SCK is disabled. Normally, SCK is not externally driven if the device is in the internal SCK timing mode. However, certain applications may require an external driver on SCK ...

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... SCK and the last bit of the conversion result can be latched on the 32nd rising edge of SCK. After the 32nd rising edge, SDO goes HIGH (EOC = 1) indicating a new conversion is in progress. SCK remains HIGH during the conversion. LTC2412 ...

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... CC During the conversion period, the undershoot and/or overshoot of a fast digital signal connected to the LTC2412 pins may severely disturb the analog to digital conversion process. Undershoot and overshoot can occur because of the impedance mismatch at the converter pin when the transition time of an external control signal is less than twice the propagation delay from the driver to LTC2412 ...

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... Parallel termination near the LTC2412 pin will eliminate this problem but will increase the driver power dissipation. A series resistor between 27 and 56 placed near the driver or near the LTC2412 pin will also eliminate this problem without additional power dissipation. The actual resistor value depends upon the trace impedance and connection topology ...

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... The effect of this input dynamic current can be analyzed using the test circuit of Figure 12. The C includes the LTC2412 pin capacitance (5pF typical) plus the capacitance of the test fixture used to obtain the results shown in Figures 13 and 14. A careful implementation can ...

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... U U APPLICATIO S I FOR ATIO of input multiplexers, wires, connectors or sensors, the LTC2412 can maintain its exceptional accuracy while operating with relative large values of source resistance as shown in Figures 13 and 14. These measured results may be slightly different from the first order approximation suggested earlier because they include the effect of the actual second order input network together with the non- linear settling process of the input amplifiers ...

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... A 100 source resistance will create a 0.1 V typical and 1 V maximum offset voltage. Reference Current In a similar fashion, the LTC2412 samples the differential reference pins REF charge to and from the external driving circuits thus producing a dynamic reference current. This current does not change the converter offset, but it may degrade the gain and INL performance ...

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... The accuracy of the internal clock over the entire temperature and power supply range is typical better than 0.5%. Such a specification can also be easily achieved by pins when large C REF an external clock. When relatively stable resistors LTC2412 0.01 F REF C = 0.001 F REF ...

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... EOSC internal oscillator is used and the notch is set at 60Hz There is no significant difference in the LTC2412 perfor- mance between these two operation modes. An increase in f translate into a proportional increase in the maximum output data rate. This substantial advantage is neverthe- less accompanied by three potential effects, which must be carefully considered ...

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... Figure 27. Resolution (INL MAX vs Output Data Rate and Temperature W U 7000 6000 5000 4000 3000 2000 1000 2412 F23 Figure 24. +FS Error vs Output Data Rate and Temperature 2412 F25 ) 2412 F27 1LSB) LTC2412 REF = 5V – REF = GND + IN = 3.75V – 1.25V F = EXTERNAL OSCILLATOR ...

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... When external amplifiers are driving the LTC2412, the ADC input referred system noise calculation can be simpli- fied by Figure 32. The noise of an amplifier driving the LTC2412 input pin can be modeled as a band limited white noise source. Its bandwidth can be approximated by the bandwidth of a single pole lowpass filter with a corner ...

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... EOSC ratio f /153600, the Figure 32 plot accuracy begins to EOSC decrease, but in the same time the LTC2412 noise floor rises and the noise contribution of the driving amplifiers lose significance. Normal Mode Rejection and Antialiasing One of the advantages delta-sigma ADCs offer over con- ventional ADCs is on-chip digital filtering ...

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... N tions, minimal (if any) antialias filtering is required in front of the LTC2412. If passive RC components are placed in value. front of the LTC2412, the input dynamic current should be N considered (see Input Current section). In cases where large effective RC time constants are used, an external buffer amplifier may be required to minimize the effects of dynamic input current ...

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... In Figure 39, the LTC2412 uses the internal oscillator with the notch set at 60Hz (F = LOW) and in Figure 40 it uses the internal oscillator with the notch set at 50Hz (F = HIGH) ...

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... LTC2412 U U APPLICATIO S I FOR ATIO 0 –20 –40 – 60 –80 –100 –120 0 15 Figure 39. Measured Input Normal Mode Rejection vs Input Frequency with Input Perturbation of 150% Full Scale (60Hz Notch) 0 –20 –40 – 60 –80 –100 –120 0 12.5 25 37.5 50 62.5 75 87.5 100 112.5 125 137.5 150 162.5 175 187.5 200 Figure 40 ...

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... TYP .015 .004 45 .053 – .068 (0.38 0.10) (1.351 – 1.727) 0 – 8 TYP .008 – .012 (0.203 – 0.305) LTC2412 .189 – .196* (4.801 – 4.978) .009 (0.229 REF .150 – .157** (3.810 – 3.988) ...

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... LTC2424/LTC2428 4-/8-Channel, 20-Bit, No Latency LTC2440 High Speed, Low Noise 24-Bit ADC Linear Technology Corporation 36 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 5V 1 4 REF LTC2412 CH0 5 1 – CH0 6 + CH1 7 2 CH1¯ 3 – REF 8,9,10,15,16 ...