LTC2494 Linear Technology, LTC2494 Datasheet
LTC2494
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LTC2494 Summary of contents
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... The LTC2494 can be confi gured to provide a progammable gain from 1 to 256 in 8 steps. The LTC2494 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 is selected, is valid ...
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... MUXOUTN ................................–0. Digital Input Voltage ......................–0. Digital Output Voltage ...................–0. Operating Temperature Range LTC2494C ................................................ 0°C to 70°C www.DataSheet4U.com LTC2494I ............................................. –40°C to 85°C Storage Temperature Range ................... –65°C to 150°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC2494CUHF#PBF ...
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... IN REF CC + – 2.5V GND REF + – 2.5V GND (Notes 7, 9) REF + – 2.5V GND (Notes 8, 9) REF LTC2494 The denotes the specifi cations which ● = 25°C. (Notes MIN TYP MAX 16 ● ● 0 ● 32 REF 0.1 REF ● ...
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... LTC2494 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 is in internal SCK mode of operation such that the = 307.2kHz ±2% (external EOSC SCK pin is used as a digital output. LTC2494 The denotes the specifi cations which apply over the ● MIN TYP ● ...
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... LTC2494 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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... REF = 2.5V – REF = GND 0 GND IN(CM 25°C A 0.1 0 –0.1 –0.2 –0.3 4.3 2.7 3.1 3.5 3 (V) CC 2494 G16 LTC2494 RMS Noise vs Temperature (T 1 REF 0 GND IN(CM) GAIN = 256 0.8 0.7 0.6 0.5 0 –45 –30 – TEMPERATURE (°C) 2494 G11 Offset Error vs V IN(CM) 0 ...
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... LTC2494 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 – GND ...
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... 230 GND IN(CM GND O 220 T = 25°C A 210 200 190 180 170 160 5 5 (V) REF 2494 G34 LTC2494 Noise Histogram = 2.5V) (2x Speed Mode) 16 10,000 CONSECUTIVE READINGS REF GAIN = 128 25° 0.75 1.25 181.4 183 ...
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... LTC2494 TYPICAL PERFORMANCE CHARACTERISTICS PSRR vs Frequency at V (2x Speed Mode 4.1V DC ±1. REF = 2.5V –20 – REF = GND + IN = GND – – GND F = GND 25°C A –60 –80 –100 www.DataSheet4U.com –120 –140 FREQUENCY AT V PIN FUNCTIONS GND (Pins 31, 32, 33): Ground. Multiple ground pins internally connected for optimum ground cur- rent fl ...
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... PCB ground plane. For prototyping purposes, this pin may remain fl oating. TEMP MUXOUTP ADCINP + – DIFFERENTIAL MUX 3RD ORDER ΔΣ MODULATOR MUXOUTN ADCINN Figure 1. Functional Block Diagram LTC2494 INTERNAL OSCILLATOR F AUTOCALIBRATION O (INT/EXT) AND CONTROL SDI SCK SERIAL INTERFACE SDO CS ...
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... LTC2494 TEST CIRCUITS SDO 1.69k Hi Hi-Z OH www.DataSheet4U.com TIMING DIAGRAMS CS Hi-Z SDO SCK SDI SLEEP CS Hi-Z SDO t 5 SCK SDI SLEEP 20pF LOAD 2494 TC01 Timing Diagram Using Internal SCK (SCK HIGH with CS↓ KQMIN DATA IN/OUT Timing Diagram Using External SCK (SCK LOW with CS↓ ...
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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 LTC2494 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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... For correct converter operation must be positive (REF > REF REF 14 The LTC2494 differential reference input range is 0. For the simplest operation, REF CC V and REF CC put noise is determined by the thermal noise of the front end circuits, and as such, its value in nano volts is nearly constant with reference voltage. A decrease in reference voltage will not signifi ...
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... SCK while CS is low. OUTPUT DATA FORMAT The LTC2494 serial output stream is 24 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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... If both Bit 21 and Bit 20 are HIGH, the differential input voltage is above www.DataSheet4U.com +FS. If both Bit 21 and Bit 20 are LOW, the differential input voltage is below –FS. The function of these bits is summarized in Table 1. Table 1. LTC2494 Status Bits Bit 23 EOC Input Range V ≥ 0.5 • V ...
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... IN IN INPUT DATA FORMAT The LTC2494 serial input word is 16 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, GS2, GS1, GS0) is used to select the frequency rejection, speed mode (1x, 2x), temperature measurement, and gain ...
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... LTC2494 APPLICATIONS INFORMATION Table 3 Channel Selection MUX ADDRESS ODD/ SGL SIGN www.DataSheet4U.com – ...
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... Rejection Mode (FA, FB) The LTC2494 includes a high accuracy on-chip oscillator with no required external components. Coupled with an integrated 4th order digital low pass fi lter, the LTC2494 rejects line frequency noise. In the default mode, the LTC2494 simultaneously rejects 50Hz and 60Hz by at least 87dB. If more rejection is required, the LTC2494 can be confi ...
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... K SERIAL INTERFACE TIMING MODES . REF The LTC2494’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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... TEMPERATURE (K) Figure 4. Internal PTAT Digital Output vs Temperature Table 6. LTC2494 Interface Timing Modes CONFIGURATION External SCK, Single Cycle Conversion External SCK, 3-Wire I/O Internal SCK, Single Cycle Conversion Internal SCK, 3-Wire I/O, Continuous Conversion External Serial Clock, Single Cycle Operation ...
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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). 22 2.7V TO 5.5V 10μ LTC2494 0.1μ REFERENCE REF SDI VOLTAGE 30 38 – 0. ...
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... SGL ODD EN2 “0” SIG MSB BIT 22 BIT 21 BIT 20 BIT 19 BIT 18 BIT 17 BIT 16 BIT 15 BIT 14 BIT 13 DATA INPUT/OUTPUT Figure 8. External Serial Clock, 3-Wire Operation ( LTC2494 = EXTERNAL OSCILLATOR 35 = INTERNAL OSCILLATOR 34 38 4-WIRE SPI INTERFACE DON'T CARE ...
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... SCK will occur and the conversion result is shifted out the SDO pin on the falling edge of SCK. The serial input word (SDI) is shifted into the device on the rising edge of SCK. 2.7V TO 5.5V 10μ LTC2494 0.1μ REFERENCE REF SDI VOLTAGE 30 38 – ...
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... EN SGL ODD “0” SIG MSB BIT 22 BIT 21 BIT 20 BIT 19 BIT 18 BIT 17 BIT 16 BIT 15 BIT 14 BIT 13 DATA INPUT/OUTPUT LTC2494 exceeds 2V. An internal weak CC = EXTERNAL OSCILLATOR 35 = INTERNAL OSCILLATOR OPTIONAL 10k 38 4-WIRE SPI INTERFACE 37 36 1,3,4,5,6,31,32,33, ...
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... SCK mode on the next falling edge of CS. This can be avoided by adding an external 10k pull-up resistor to the SCK pin. Whenever SCK is LOW, the LTC2494’s internal pull-up at SCK is disabled. Normally, SCK is not externally driven if the device is operating in the internal SCK timing mode. ...
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... APPLICATIONS INFORMATION PRESERVING THE CONVERTER ACCURACY The LTC2494 is designed to reduce as much as possible sensitivity to device decoupling, PCB layout, anti-aliasing circuits, line frequency perturbations, and temperature sensitivity. In order to achieve maximum performance a few simple precautions should be observed. Digital Signal Levels The LTC2494’s digital interface is easy to use. Its digital ...
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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 LTC2494, leading to little degradation in accuracy. Mismatches in source ( ) ( ) − ...
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... The LTC6078 is an excellent amplifi er for this function. It operates with supply voltages as low as 2.7V and its noise level is 18nV/√Hz. The Easy Drive input technology of the LTC2494 enables an RC network to be added directly to the output of the LTC6078. The capacitor reduces the magnitude of the current spikes seen at the input to the ADC and the resistor isolates the capacitor load from the op-amp output enabling stable operation ...
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... LTC2494 APPLICATIONS INFORMATION REF + V = 3.75V IN 70 – 1.25V GND 25° 0.01μF REF 0.001μF REF C = 100pF REF 0pF REF – 100 1k www.DataSheet4U.com R (Ω) SOURCE Figure 14. +FS Error vs R SOURCE 10 0 – 0.01μ ...
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... Normal Mode Rejection and Anti-aliasing One of the advantages delta-sigma ADCs offer over conventional ADCs is on-chip digital fi ltering. Combined with a large oversample ratio, the LTC2494 signifi cantly www.DataSheet4U.com simplifi es anti-aliasing fi lter requirements. Additionally, the input current cancellation feature allows external low pass fi ...
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... LTC2494. From these curves shown that the rejection performance is maintained even in extremely noisy environments. Using the 2x speed mode of the LTC2494 alters the rejec- tion characteristics around DC and multiples of f device bypasses the offset calibration in order to increase the output rate ...
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... REF V = 7.5V IN(P- 2.5V IN(CM) (150% OF FULL SCALE 25°C A 2494 F27 Figure 29. Input Normal Mode Rejection 2x Speed Mode = EOSC Figure 30. Input Normal Mode Rejection 2x Speed Mode with and Without Running Averaging LTC2494 0 –20 –40 –60 –80 –100 –120 ...
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... LTC2494 APPLICATIONS INFORMATION IN(CM) REF(CM REF EXT CLOCK 85° 25°C A – www.DataSheet4U.com OUTPUT DATA RATE (READINGS/SEC) Figure 31. Offset Error vs Output Data Rate and Temperature 25°C, 85° ...
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... DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE LTC2494 0.70 ± 0.05 PACKAGE OUTLINE PIN 1 NOTCH R = 0.30 TYP OR 3.15 ± ...
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... Pin Compatible with LTC2480/LTC2484 2 C Interface Pin Compatible with LTC2481/LTC2485 Pin Compatible with LTC2480/LTC2482 2 C Interface, and Pin Compatible with LTC2481/LTC2483 Pin Compatible with LTC2494/LTC2449/LTC2498 Pin Compatible with LTC2494/LTC2496/LTC2449 www.linear.com ● SDI ΔΣ ADC SCK WITH EASY DRIVE SDO INPUTS CS 0.1μ ...