LTC2488 LINER [Linear Technology], LTC2488 Datasheet
LTC2488
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LTC2488 Summary of contents
Page 1
... It automatically rejects line frequencies of 50Hz and 60Hz simultaneously. The LTC2488 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 ................................–0. Digital Input Voltage ......................–0. Digital Output Voltage ...................–0. Operating Temperature Range LTC2488C ................................................ 0°C to 70°C LTC2488I ............................................. –40°C to 85°C Storage Temperature Range ................... –65°C to 150°C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T ...
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... REF ) + Sleep Mode GND – Sleep Mode GND + Sleep Mode, REF – Sleep Mode, REF 1.8MHz IN P-P LTC2488 MIN TYP MAX ● (Note 5) 140 ● (Note 5) 140 ● (Note 5) 140 ● (Notes 5, 7) 110 120 (Notes 5, 8) ● ...
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... LTC2488 DIGITAL INPUTS AND DIGITAL OUTPUTS full operating temperature range, otherwise specifi cations are at T SYMBOL PARAMETER High Level Input Voltage ( ⎯ C ⎯ Low Level Input Voltage ( ⎯ C ⎯ High Level Input Voltage (SCK Low Level Input Voltage (SCK) IL Digital Input Current ( ⎯ ...
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... SCK pin is used as a digital input. The frequency of the clock signal driving SCK during the data output is f Note 16: Refer to Applications Information section for performance vs data rate graphs. Note 17: The converter in internal SCK mode of operation such that the SCK pin is used as a digital output. LTC2488 MIN TYP MAX UNITS 10 4000 0 ...
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... LTC2488 TYPICAL PERFORMANCE CHARACTERISTICS Integral Nonlinearity ( 5V) CC REF REF 2.5V IN(CM GND O 1 –45°C 25°C 0 85°C –1 –2 –3 –2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 2 INPUT VOLTAGE (V) 2488 G01 Total Unadjusted Error ( 5V) CC REF ...
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... GND O 1 SCK = NC 1.6 SDO = NC SDI = GND 1.4 1 1.0 0.8 0 2.7V CC 0.4 0.2 0 –45 –30 – TEMPERATURE (°C) LTC2488 On-Chip Oscillator Frequency 310 308 306 304 302 300 75 90 2.5 3.5 4.0 4.5 3.0 V (V) CC 2488 G11 PSRR vs Frequency 4.1V DC ±0. ...
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... LTC2488 PIN FUNCTIONS F (Pin 1): Frequency Control Pin. Digital input that controls O the internal conversion clock rate. When F ground, the converter uses its internal oscillator running at 307.2kHz. The conversion clock may also be overridden by driving the F pin with an external clock in order to change O the output rate and the digital fi lter rejection null. ...
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... SLEEP SDO C = 20pF LOAD OH OH 2488 TC01 t KQMIN t KQMAX DATA IN/OUT t KQMIN t KQMAX DATA IN/OUT LTC2488 V CC 1.69k C = 20pF LOAD Hi Hi-Z OL 2488 TC02 t 2 Hi-Z CONVERSION 2488 TD01 t 2 Hi-Z CONVERSION 2488 TD02 2488f ...
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... ADC or when ⎯ C ⎯ brought HIGH. The device automatically initiates a new conversion and the cycle repeats. Through timing control of the ⎯ C ⎯ S and SCK pins, the LTC2488 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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... APPLICATIONS INFORMATION enables external RC networks and high impedance sen- sors to directly interface to the LTC2488 without external amplifi ers. The remaining common mode input current is eliminated by either balancing the differential input impedances or setting the common mode input equal to the common mode reference (see Automatic Differential Input Current Cancellation Section) ...
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... SCK while ⎯ C ⎯ low. OUTPUT DATA FORMAT The LTC2488 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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... For differential input voltages below –FS, the conversion result is clamped to the value –FS – 1LSB. INPUT DATA FORMAT The LTC2488 serial input word is 8 bits long. The input bits (SGL, ODD, A2, A1, A0) are used to select the input channel. 3 ...
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... SERIAL INTERFACE TIMING MODES The LTC2488’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 DATA INPUT/OUTPUT Figure 4. External Serial Clock, Single Cycle Operation LTC2488 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR 4-WIRE SPI INTERFACE DON'T CARE LSB BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 Hi-Z CONVERSION ...
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... SDI pin on the rising edge of SCK. On the 24th falling edge of SCK, SDO goes HIGH, indicating a new conversion has begun. This data now serves as ⎯ E ⎯ O ⎯ C for the next conversion. 2. LTC2488 10µ REFERENCE + REF SDI VOLTAGE 14 3 0.1µ ...
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... SCK (see Figure 8). On the ris- ing edge of ⎯ C ⎯ the device aborts the data output state and immediately initiates a new conversion. In order to program a new input channel, 8 SCK clock pulses are LTC2488 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR 19 20 ...
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... POR cycle; therefore, the internal serial clock timing mode is automatically selected if SCK is fl oating or driven HIGH. During the conversion, the SCK and the serial data output 18 2. LTC2488 10µ REFERENCE REF SDI VOLTAGE 14 3 0.1µF – ...
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... EN SGL ODD “0” SIG MSB DATA INPUT/OUTPUT Figure 9. Internal Serial Clock, Continuous Operation LTC2488 = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR V CC OPTIONAL 10k 4-WIRE SPI INTERFACE 9 10 DON'T CARE Hi-Z BIT 14 BIT 13 CONVERSION = EXTERNAL OSCILLATOR = INTERNAL OSCILLATOR V CC ...
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... These issues are avoided when using the internal oscillator. Driving the Input and Reference The input and reference pins of the LTC2488 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 ...
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... EOSC CH3, COM), on the other hand, are typically driven from larger source resistances. Source resistances up to 10k may interface directly to the LTC2488 and settle completely; however, the addition of external capacitors at the input terminals in order to fi lter unwanted noise (anti-aliasing) results in incomplete settling. ...
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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 LTC2488, 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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... One of the advantages delta-sigma ADCs offer over conventional ADCs is on-chip digital fi ltering. Combined C = 0.1µF with a large oversample ratio, the LTC2488 signifi cantly REF simplifi es anti-aliasing fi lter requirements. Additionally, the input current cancellation feature allows external low pass fi ltering without degrading the DC performance 0.01µ ...
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... Figure 19 shows mea- surement results for the rejection of a 7.5V peak-to-peak noise source (150% of full scale) applied to the LTC2488. From this curve shown that the rejection performance is maintained even in extremely noisy environments. ...
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... Easy Drive also enables very low power, low bandwidth amplifi ers to drive the input to the LTC2488. As shown in Figure 28, 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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... LTC2488 APPLICATIONS INFORMATION IN(CM) REF(CM REF EXT CLOCK 85° 25°C A – OUTPUT DATA RATE (READINGS/SEC) 2488 F20 Figure 20. Offset Error vs Output Data Rate and Temperature 25°C, 85°C ...
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... LTC DWG # 05-08-1708 Rev A) 0.70 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 3.30 ±0.05 (2 SIDES) 4.00 ±0.10 (2 SIDES 0.05 TYP 3.00 ±0.10 1.70 ± 0.05 (2 SIDES) (2 SIDES) 0.75 ±0.05 0.00 – 0.05 LTC2488 R = 0.115 0.40 ± 0.10 TYP 8 14 PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER (DE14) DFN 0905 REV 0.25 ± 0.05 0.50 BSC 3.30 ±0.05 (2 SIDES) BOTTOM VIEW—EXPOSED PAD 27 ...
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... Output Rate, 220nV Noise, Simultaneous 50Hz/60Hz Rejection 8kHz Output Rate, 200nV Noise, Simultaneous 50Hz/60Hz Rejection Pin Compatible with 16-Bit and 24-Bit Versions Pin Compatible with 16-Bit and 24-Bit Versions Pin Compatible with LTC2488 Timing Compatible with LTC2492 8kHz Output Rate, Variable Speed Resolution www.linear.com ● ...