LTC2498 Linear Technology, LTC2498 Datasheet
LTC2498
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LTC2498 Summary of contents
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... The integrated temperature sensor offers 1/30th °C resolution and 2°C absolute accuracy. The LTC2498 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. Access to the multiplexer output enables optional external amplifi ...
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... ADCINN, ADCINP , MUXOUTP , MUXOUTN ................................–0. Digital Input Voltage ......................–0. Digital Output Voltage ...................–0. Operating Temperature Range LTC2498C ................................................ 0°C to 70°C www.DataSheet4U.com LTC2498I.............................................. –40°C to 85°C Storage Temperature Range ................... –65°C to 150°C ORDER INFORMATION LEAD FREE FINISH ...
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... GND (Notes 7, 9) REF + – 2.5V GND (Notes 8, 9) REF l The denotes the specifi cations which apply over the full operating = 25°C. (Note 3) A CONDITIONS + Voltage LTC2498 l The denotes the specifi cations which = 25°C. (Notes MIN TYP MAX 0 0.6 27.8 28.0 28.2 93 ...
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... LTC2498 ANALOG INPUT AND REFERENCE temperature range, otherwise specifi cations are at T SYMBOL PARAMETER – 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 cant Bit of the Output Code ...
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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. LTC2498 l The denotes the specifi cations which apply over the MIN TYP l ...
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... LTC2498 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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... Offset Error 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 2498 G16 LTC2498 RMS Noise vs Temperature (T 1 REF 0 GND IN(CM) 0.8 0.7 0.6 0.5 0 –45 0 –30 –15 15 TEMPERATURE (°C) 2498 G11 Offset Error vs V IN(CM) 0 ...
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... LTC2498 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 30 –45 –30 – TEMPERATURE (°C) PSRR vs Frequency 4.1V DC ±1. 2.5V REF – GND – GND –40 ...
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... GND IN(CM GND O 220 T = 25°C A 210 200 190 180 170 160 5 (V) REF 2498 G34 LTC2498 Noise Histogram = 2.5V) (2x Speed Mode) 16 10,000 CONSECUTIVE READINGS REF GAIN = 256 25° 179 181 ...
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... LTC2498 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. MUXOUTP ADCINP + – DIFFERENTIAL MUX 3RD ORDER ΔΣ MODULATOR MUXOUTN ADCINN Figure 1. Functional Block Diagram LTC2498 INTERNAL OSCILLATOR F AUTOCALIBRATION O (INT/EXT) AND CONTROL SDI SCK SERIAL INTERFACE SDO ...
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... LTC2498 TEST CIRCUITS SDO 1.69k Hi Hi-Z OH www.DataSheet4U.com TIMING DIAGRAMS CS SDO SCK SDI SLEEP CS SDO t 5 SCK SDI SLEEP 20pF LOAD 2498 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 LTC2498 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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... V ). For correct converter operation must be positive (REF > REF REF The LTC2498 differential reference input range is 0. For the simplest operation, REF 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 ...
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... SCK while CS is low. OUTPUT DATA FORMAT The LTC2498 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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... 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 www.DataSheet4U.com input voltage is below –FS. The function of these bits is summarized in Table 1. Table 1. LTC2498 Status Bits Input Range Bit 31 EOC V ≥ 0.5 • V ...
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... IN IN INPUT DATA FORMAT The LTC2498 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 (1x, 2x), and temperature mea- surement ...
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... LTC2498 APPLICATIONS INFORMATION Table 3 Channel Selection MUX ADDRESS ODD/ SGL SIGN www.DataSheet4U.com – ...
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... Rejection Mode (FA, FB) The LTC2498 includes a high accuracy on-chip oscillator with no required external components. Coupled with an integrated 4th order digital low pass fi lter, the LTC2498 re- jects line frequency noise. In the default mode, the LTC2498 simultaneously rejects 50Hz and 60Hz by at least 87dB. If more rejection is required, the LTC2498 can be confi ...
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... SERIAL INTERFACE TIMING MODES The LTC2498’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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... 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 6. External Serial Clock, Single Cycle Operation LTC2498 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR SPD DON'T CARE BIT 20 BIT 19 ...
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... 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. On the falling edge of EOC, the conversion result is load- 2.7V TO 5.5V 10μ LTC2498 0.1μ REFERENCE REF SDI VOLTAGE 38 30 – ...
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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 au- tomatically begins. SDO goes HIGH (EOC = 1) and SCK LTC2498 = 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 2.7V TO 5.5V 10μ LTC2498 0.1μ REFERENCE + REF SDI VOLTAGE 30 38 – REF SCK 0 ...
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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 LTC2498 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR V CC OPTIONAL 10k 4-WIRE SPI INTERFACE EN2 ...
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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 LTC2498 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 LTC2498 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 LTC2498, leading to little degradation in accuracy. Mismatches in source impedances lead to gain errors proportional to the dif- ference between the common mode input and common mode reference ...
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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 LTC2498 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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... F S EOSC of frequency 0.01μF REF When using the internal oscillator, the LTC2498 is designed to reject line frequencies. As shown in Figure 21, rejec- tion nulls occur at multiples of frequency f 800 1000 determined by the input control bits FA and 60Hz or 55Hz for simultaneous rejection). Multiples of 2498 F16 ...
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... Traditional high order delta-sigma modulators suffer from potential instabilities at large input signal levels. The proprietary architecture used for the LTC2498 third www.DataSheet4U.com order modulator resolves this problem and guarantees stability with input signals 150% of full-scale. In many ...
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... LTC2498. From these curves shown that the rejection performance is maintained even in extremely noisy environments. Using the 2x speed mode of the LTC2498 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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... EXT CLOCK O RES = LOG 2 (V /NOISE ) REF RMS 10 90 100 OUTPUT DATA RATE (READINGS/SEC) 2498 F33 Figure 34. Resolution (Noise vs Output Data Rate and Temperature LTC2498 3500 IN(CM) REF(CM REF 3000 F = EXT CLOCK O 2500 T = 85°C A 2000 ...
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... LTC2498 APPLICATIONS INFORMATION IN(CM) REF(CM EXT CLOCK 25° REF 5 0 – 5V 2.5V CC REF – www.DataSheet4U.com OUTPUT DATA RATE (READINGS/SEC) Figure 36. Offset Error vs Output Data Rate and Reference Voltage 34 24 ...
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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 LTC2498 0.70 0.05 PACKAGE OUTLINE PIN 1 NOTCH R = 0.30 TYP OR ...
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... Pin Compatible with LTC2482/LTC2484 2 Pin Compatible with LTC2483/LTC2485 C Pin Compatible with LTC2480/LTC2484 2 Pin Compatible with LTC2481/LTC2485 C Interface Pin Compatible with LTC2480/LTC2482 2 Pin Compatible with LTC2481/LTC2483 C Interface, and Pin Compatible with LTC2498/LTC2449 www.linear.com ● SDI ΔΣ ADC SCK WITH EASY DRIVE SDO INPUTS CS 0.1μF 0.1μ ...