LTC2492 Linear Technology, LTC2492 Datasheet
LTC2492
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LTC2492 Summary of contents
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... The integrated temperature sensor offers 1/30th °C resolution and 2°C absolute accuracy. The LTC2492 allows a wide common mode input range ( combination of single-ended or differential inputs can be selected and the fi rst conversion after a new channel selection is valid ...
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... REF , REF .................................. – 0. Digital Input Voltage ..................... – 0. Digital Output Voltage .................. – 0. Operating Temperature Range LTC2492C ................................................ 0°C to 70°C LTC2492I..............................................– 40°C to 85°C Storage Temperature Range ...................– 65°C to 150°C www.DataSheet4U.com ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL ...
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... – 2.5V GND REF + – 2.5V GND (Notes 7, 9) REF + – 2.5V GND (Notes 8, 9) REF LTC2492 denotes the specifi cations which apply over the ● MIN TYP MAX 24 ● ● 1 ● 0.2 2 100 ● 25 0.1 ppm of V ● 25 0.1 ppm of V ...
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... LTC2492 ANALOG INPUT AND REFERENCE temperature range, otherwise specifi cations are at T SYMBOL PARAMETER + IN Absolute/Common Mode IN + (IN Corresponds to the Selected Positive Input Channel) – IN Absolute/Common Mode IN – (IN Corresponds to the Selected Negative Input Channel) V Input Differential Voltage Range ( Full Scale of the Differential Input (IN LSB Least Signifi ...
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... EOSC data rate graphs. Note 17: The converter in internal SCK mode of operation such that the = 307.2kHz ±2% (external EOSC SCK pin is used as a digital output. LTC2492 The denotes the specifi cations which apply over the ● MIN TYP ● ...
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... LTC2492 TYPICAL PERFORMANCE CHARACTERISTICS Integral Nonlinearity ( 5V) CC REF REF 2.5V IN(CM GND O 1 –45°C 25°C 0 85°C –1 www.DataSheet4U.com –2 –3 –2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 INPUT VOLTAGE (V) Total Unadjusted Error ( 5V) CC REF ...
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... CC 0.3 + REF = 2.5V – REF = GND 0 GND IN(CM 25°C A 0.1 0 –0.1 –0.2 –0.3 2.7 3.1 3.5 3.9 4 (V) CC 2492 G16 LTC2492 RMS Noise vs Temperature (T 1 REF 0 GND IN(CM) 0.8 0.7 0.6 0.5 0 – –30 –15 15 TEMPERATURE (°C) 2492 G11 Offset Error vs V IN(CM) 0 ...
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... LTC2492 TYPICAL PERFORMANCE CHARACTERISTICS On-Chip Oscillator Frequency vs Temperature 310 308 306 304 2.5V REF 302 www.DataSheet4U.com GND IN(CM GND O 300 –45 –30 – TEMPERATURE (°C) PSRR vs Frequency 4.1V DC ±1. 2.5V REF – GND – GND –40 ...
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... 196 F = GND 25°C 194 A 192 190 188 186 184 182 180 5 – (V) IN(CM) 2492 G31 LTC2492 Noise Histogram (2x Speed Mode) 16 10,000 CONSECUTIVE AVERAGE = 0.184mV READINGS REF 25° 0.75 1.25 179 181 ...
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... LTC2492 TYPICAL PERFORMANCE CHARACTERISTICS Offset Error vs V (2x Speed Mode) CC 250 V = 2.5V REF GND IN(CM) 200 F = GND 25°C A 150 100 50 www.DataSheet4U.com 0 2 2.5 3 3.5 4 4.5 V (V) CC PSRR vs Frequency at V (2x Speed Mode 4.1V DC ±1. REF = 2.5V –20 – REF = GND + IN = GND – – GND F = GND ...
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... When performing an on-chip temperature measurement, the minimum value of REF = 2V. Exposed Pad (Pin 15): Ground. This pin is ground and must be soldered to the PCB ground plane. For prototyping purposes, this pin may remain fl oating. LTC2492 – ) for all + 0.3V. Within these limits, the two CC + – ...
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... LTC2492 FUNCTIONAL BLOCK DIAGRAM V CC GND + REF – REF CH0 CH1 CH2 CH3 COM www.DataSheet4U.com TEST CIRCUITS SDO 1.69k Hi Hi TEMP SENSOR AUTOCALIBRATION AND CONTROL + – DIFFERENTIAL – MUX 3RD ORDER IN Δ∑ MODULATOR DECIMATING FIR Figure 1. Functional Block Diagram ...
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... Timing Diagram Using Internal SCK (SCK HIGH with CS↓ KQMIN DATA IN/OUT Timing Diagram Using External SCK (SCK LOW with CS↓ KQMIN DATA IN/OUT LTC2492 t 2 Hi-Z t KQMAX CONVERSION 2492 TD01 t 2 Hi-Z t KQMAX CONVERSION 2492 TD02 2492fb 13 ...
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... ADC or when CS is brought HIGH. The device automatically initiates a new conversion and the cycle repeats. Through timing control of the CS and SCK pins, the LTC2492 offers several fl exible modes of operation (internal or external SCK and free-running conversion modes). These various modes do not require programming and do not disturb the cyclic operation described above ...
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... REF and REF the device (GND must be positive (REF REF The LTC2492 differential reference input range is 0. For the simplest operation, REF CC – and REF can be shorted to GND. The converter output noise is determined by the thermal noise of the front end circuits, and as such, its value in nanovolts is nearly constant with reference voltage ...
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... SCK while CS is low. OUTPUT DATA FORMAT The LTC2492 serial output stream is 32 bits long. The fi rst bit indicates the conversion status, the second bit is always zero, and the third bit conveys sign information. ...
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... INPUT DATA FORMAT The LTC2492 serial input word is 13 bits long and contains two distinct sets of data. The fi rst set (SGL, ODD, A2, A1, A0) is used to select the input channel. The second set of data (IM, FA, FB, SPD) is used to select the frequency rejection, speed mode (1× ...
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... LTC2492 APPLICATIONS INFORMATION Table 2. Output Data Format Differential Input Voltage ≥ 0.5 • REF 0.5 • – 1LSB REF 0.25 • REF 0.25 • – 1LSB REF 0 –1LSB –0.25 • REF www.DataSheet4U.com –0.25 • – 1LSB REF –0.5 • REF V * < –0.5 • V ...
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... Rejection Mode (FA, FB) The LTC2492 includes a high accuracy on-chip oscillator with no required external components. Coupled with an integrated 4th order digital low pass fi lter, the LTC2492 rejects line frequency noise. In the default mode, the LTC2492 simultaneously rejects 50Hz and 60Hz by at least 87dB. If more rejection is required, the LTC2492 can be confi ...
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... SERIAL INTERFACE TIMING MODES The LTC2492’s 4-wire interface is SPI and MICROWIRE compatible. This interface offers several fl exible modes of operation. These include internal/external serial clock 4-wire I/O, single cycle or continuous conversion. The following sections describe each of these timing modes in detail ...
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... EN SGL ODD “0” SIG MSB BIT 30 BIT 29 BIT 28 BIT 27 BIT 26 BIT 25 BIT 24 BIT 23 BIT 22 BIT 21 DATA INPUT/OUTPUT Figure 6. External Serial Clock, Single Cycle Operation LTC2492 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR 4-WIRE SPI INTERFACE EN2 SPD ...
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... SDO pin during the convert and sleep states. EOC may be used as an interrupt to an external controller. EOC = 1 while the conversion is in progress and EOC = 0 once the conversion is complete. 2. LTC2492 10μ REFERENCE REF SDI VOLTAGE 14 3 0.1μ ...
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... SDO pin on the falling edge of SCK. The serial input word (SDI) is shifted into the device on the rising edge of SCK. After the 32nd rising edge of SCK a new conversion automatically begins. SDO goes HIGH (EOC = 1) and SCK LTC2492 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR 3-WIRE SPI INTERFACE ...
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... In order to program both the input channel and converter confi guration, CS must go high after the 16th falling edge of SCK (at this point all data has been shifted into the device). 24 2. LTC2492 10μ REFERENCE REF SDI VOLTAGE 14 3 0.1μF – ...
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... EN SGL ODD EN2 “0” SIG MSB BIT 30 BIT 29 BIT 28 BIT 27 BIT 26 BIT 25 BIT 24 BIT 23 BIT 22 BIT 21 DATA INPUT/OUTPUT Figure 11. Internal Serial Clock, Continuous Operation LTC2492 = EXTERNAL OSCILLATOR 1 = INTERNAL OSCILLATOR OPTIONAL 10k 3 4-WIRE SPI INTERFACE ...
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... This becomes diffi cult when shared control lines are used and multiple refl ections occur. Parallel termination near the input pin of the LTC2492 will eliminate this problem, but will increase the driver power , EOCtest dissipation. A series resistor from 27Ω ...
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... APPLICATIONS INFORMATION Driving the Input and Reference The input and reference pins of the LTC2492 are connected directly to a switched capacitor network. Depending on the relationship between the differential input voltage and the differential reference voltage, these capacitors are switched between these four pins. Each time a capacitor is switched between two of these pins, a small amount of charge is transferred. A simplifi ...
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... For the case of balanced input impedances, the common mode input current effects are rejected by the large CMRR of the LTC2492, leading to little degradation in accuracy. Mismatches in source impedances lead to gain errors proportional to the difference between the common mode input and common mode reference ...
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... One of the advantages delta-sigma ADCs offer over conventional ADCs is on-chip digital fi ltering. Combined C = 0.01μF REF with a large oversample ratio, the LTC2492 signifi cantly simplifi es anti-aliasing fi lter requirements. Additionally, the input current cancellation feature allows external low C = 0.1μF REF pass fi ...
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... F /20 when operating with an external oscillator S EOSC of frequency F . EOSC When using the internal oscillator, the LTC2492 is designed to reject line frequencies. As shown in Figure 20, rejection nulls occur at multiples of frequency f www.DataSheet4U.com 0 –10 –20 –30 –40 –50 – ...
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... Figures 25 and 26 show measurement results for the rejection of a 7.5V peak-to-peak noise source (150% of full scale) applied 2492 F22 to the LTC2492. From these curves shown that the rejection performance is maintained even in extremely noisy environments ...
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... LTC2492 APPLICATIONS INFORMATION Using the 2x speed mode of the LTC2492 alters the rejection characteristics around DC and multiples of f bypasses the offset calibration in order to increase the output rate. The resulting rejection plots are shown in Figures 27 and 28. 1x type frequency rejection can be achieved using the 2x mode by performing a running average of the conversion results (see Figure 29) ...
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... RES = LOG 2 (V /NOISE ) REF RMS 10 90 100 OUTPUT DATA RATE (READINGS/SEC) 2492 F35 Figure 36. Resolution (Noise vs Output Data Rate and Reference Voltage LTC2492 3500 IN(CM) REF(CM REF 3000 F = EXT CLOCK O 2500 T = 85°C A 2000 ...
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... Easy Drive also enables very low power, low bandwidth amplifi ers to drive the input to the LTC2492. As shown in Figure 38, CH2 is driven by the LT1494. The LT1494 has excellent DC specs for an amplifi er with 1.5μA supply current (the maximum offset voltage is 150μ ...
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... Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1708 Rev A) 0.70 ±0.05 3.30 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 3.00 REF 4.00 ±0.10 (2 SIDES 0.05 TYP 3.00 ±0.10 (2 SIDES) 0.75 ±0.05 0.00 – 0.05 LTC2492 R = 0.115 0.40 ± 0.10 TYP 8 14 3.30 ±0.10 1.70 ± 0.10 PIN 1 NOTCH R = 0.20 OR 0.35 45° CHAMFER (DE14) DFN 0806 REV 0.25 ± 0.05 0.50 BSC 3.00 REF BOTTOM VIEW— ...
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... LTC2485 24-Bit Δ∑ ADC with Easy Drive Inputs, I Temperature Sensor LTC2488 2-Channel and 4-Channel 16-Bit Δ∑ ADC with Easy Drive Inputs Pin Compatible with LTC2492 LTC2496/ 16-Channel/8-Channel 16-Bit/24-Bit Δ∑ ADC with Easy Drive LTC2498 Inputs, and SPI Interface ...