LTC2487 Linear Technology, LTC2487 Datasheet
LTC2487
Available stocks
Related parts for LTC2487
LTC2487 Summary of contents
Page 1
... The integrated temperature sensor offers 1/2°C resolution and 2°C absolute accuracy. The LTC2487 can be configured to provide a programmable gain from 1 to 256 in 8 steps. The LTC2487 allows a wide common mode input range ( combination of single-ended or differential inputs can be selected and the first conversion, after a new channel is selected, is valid ...
Page 2
... Digital Input Voltage ......................–0. Digital Output Voltage ...................–0. Operating Temperature Range LTC2487C ................................................ 0°C to 70°C www.DataSheet4U.com LTC2487I ............................................. –40°C to 85°C Storage Temperature Range ................... –65°C to 150°C orDer inForMaTion LEAD FREE FINISH TAPE AND REEL LTC2487CDE#PBF ...
Page 3
... V REF CC + – 2.5V ≤ V ≤ GND ≤ ≤ V REF CC + – 2.5V GND REF + – 2.5V GND (Notes REF LTC2487 The denotes the specifications which ● = 25°C. (Notes MIN TYP MAX ● 1 ● 0.5 5 ● ● 0.1 32 ● 0 ...
Page 4
... LTC2487 analog inpuT anD reFerence temperature range, otherwise specifications 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 ...
Page 5
... Note 12: The output noise includes the contribution of the internal calibration operations. Note 13: Guaranteed by design and test correlation. Note 14: C Note 15: All values refer to V Note 16: Refer to Applications Information section for Performance vs Data Rate graphs. LTC2487 MIN TYP MAX 2.7 5.5 ● 160 275 ● ...
Page 6
... LTC2487 Typical perForMance characTerisTics Integral Nonlinearity ( 5V) CC REF REF 2.5V IN(CM GND O 1 –45°C 25°C 0 85°C www.DataSheet4U.com –1 –2 –3 –2.5 –2 –1.5 –1 –0.5 0 0.5 INPUT VOLTAGE (V) Total Unadjusted Error ( 5V) CC REF ...
Page 7
... GND O 0.1 0 –0.1 –0.2 –0 – IN(CM) 2487 G14 Offset Error vs V 0.3 0.2 0.1 0 –0.1 –0.2 –0 4.7 5.1 5.5 V 2487 G17 LTC2487 ) 2487 G12 IN(CM (V) 2487 G15 REF – REF = GND GND IN(CM 25° ...
Page 8
... LTC2487 Typical perForMance characTerisTics On-Chip Oscillator Frequency vs Temperature 310 308 306 304 www.DataSheet4U.com 2.5V REF 302 GND IN(CM GND O 300 –45 –30 – TEMPERATURE (°C) PSRR vs Frequency 4.1V DC ±1. 2.5V REF – GND – GND – GND ...
Page 9
... Offset Error vs V REF (2x Speed Mode) 240 230 GND IN(CM GND O 220 T = 25°C A 210 200 190 180 170 160 (V) REF 2487 G35 LTC2487 RMS = 0.85µV AVERAGE = 0.184mV 183.8 186.2 188.6 2487 G30 2487 G33 5 2487fa ...
Page 10
... I SCL (Pin 4): Serial Clock Pin of the I LTC2487 can only act as a slave and the SCL pin only ac- cepts an external serial clock. Data is shifted into the SDA pin on the rising edges of the SCL clock and output through the SDA pin on the falling edges of the SCL clock ...
Page 11
... TEMP SENSOR + – DIFFERENTIAL MUX – 3RD ORDER IN ∆Σ MODULATOR LTC2487 + – , REF (Pin 13, Pin 14): Differential Reference Input. as long as the reference positive input remains more positive than the negative reference – least 0.1V. The differential voltage (V + – ...
Page 12
... The device will not acknowledge an external request dur- ing the conversion state. After a conversion is finished, the device is ready to accept a read/write request. Once the LTC2487 is addressed for a read operation, the device begins outputting the conversion result under the control of the serial clock (SCL). There is no latency in the conver- sion result ...
Page 13
... This converter accepts a truly differential external reference voltage. The absolute/common mode voltage range for the + REF and REF the device (GND must be positive (REF REF The LTC2487 differential reference input range is 0. For the simplest operation, REF CC V and REF CC . Moreover, the CC ...
Page 14
... The serial clock line, SCL, is always an input to the LTC2487 and the serial data line SDA is bidirectional. The device supports the standard mode and the fast mode for data transfer speeds up to 400kbits/s. ...
Page 15
... IN + – – The INPUT DATA FORMAT The serial input word to the LTC2487 is 16 bits long and is written into the device input register in two 8-bit words. The first word (SGL, ODD, A2, A1, A0) is used to select Bit 23 Bit 22 Bit 21 Bit 20 SIG ...
Page 16
... For SGL = 0, two adjacent channels … SIG MSB D23 ACK BY ACK BY LTC2487 MASTER Figure 3a. Timing Diagram for Reading from the LTC2487 SGL ODD ACK BY LTC2487 SLEEP Figure 3b ...
Page 17
... LTC2487 CONVERTER CONFIGURATION Keep Previous Keep Previous External Input, Gain = 1, Autocalibration External Input, Gain = 4, Autocalibration External Input, Gain = 8, Autocalibration External Input, Gain = 16, Autocalibration External Input, Gain = 32, Autocalibration External Input, Gain = 64, Autocalibration External Input, Gain = 128, Autocalibration ...
Page 18
... LTC2487 rejects line frequency noise. In the default mode, the LTC2487 simultaneously rejects 50Hz and 60Hz by at least 87dB. If more rejection is required, the LTC2487 can be configured to reject 50Hz or 60Hz to better than 110dB. www.DataSheet4U.com Speed Mode (SPD) Every conversion cycle, two conversions are combined to remove the offset (default mode) ...
Page 19
... After the device acknowledges a read request, the device exits the sleep state and enters the data output state. The data output state concludes and the LTC2487 starts a new conversion once a Stop condition is issued by the master or all 24 bits of data are read out of the device. ...
Page 20
... FLOAT FLOAT FLOAT FLOAT Operation Sequence The LTC2487 acts as a transmitter or receiver, as shown in Figure 6. The device may be programmed to perform several functions. These include input channel selection, measure the internal temperature, selecting the line fre- quency rejection (50Hz, 60Hz, or simultaneous 50Hz and 60Hz speed mode and gain ...
Page 21
... WRITE (OPTIONAL) SLEEP DATA INPUT Figure 9. Start a New Conversion Without Reading Old Conversion Result LTC2487 LTC2487 … GLOBAL ADDRESS W ACK WRITE (OPTIONAL) DATA INPUT Figure 10. Synchronize Multiple LTC2487s with a Global Address Call LTC2487 R ACK READ P DATA OUTPUT CONVERSION 2487 F08 P 2487 F09 ...
Page 22
... The inputs (CH0-CH3, COM), on the other hand, are typically driven from larger source resistances. Source resistances up to 10k may interface directly to the LTC2487 and settle completely; however, the addition of external capacitors at the input terminals in order to filter unwanted noise (antialiasing) results in incomplete settling ...
Page 23
... For the case of balanced input impedances, the common mode input current effects are rejected by the large CMRR of the LTC2487, leading to little degradation in accuracy. Mismatches in source impedances lead to gain errors proportional to the dif- – ...
Page 24
... LTC2487 applicaTions inForMaTion For relatively small values of external reference capacitance (C < 1nF), the voltage on the sampling capacitor settles REF for reference impedances of many kW to 10kW will not degrade the performance (see Figures ) 12 and 13 cases where large bypass capacitors are required on the reference inputs (C > ...
Page 25
... S EOSC of frequency f . EOSC When using the internal oscillator, the LTC2487 is designed to reject line frequencies. As shown in Figure 19, rejec- tion nulls occur at multiples of frequency f determined by the input control bits FA and 60Hz or 55Hz for simultaneous rejection). Multiples of 10 ...
Page 26
... LTC2487 applicaTions inForMaTion 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 –100 www.DataSheet4U.com –110 –120 INPUT SIGNAL FREQUENCY (Hz) Figure 19. Input Normal Mode Rejection at DC –20 –40 – 60 –80 –100 –120 –20 –40 – 60 –80 –100 –120 ...
Page 27
... Figures 24 and 25 show measurement results for the rejection of a 7.5V peak-to-peak noise source (150% of full scale) applied to the LTC2487. These curves show that the rejec- tion performance is maintained even in extremely noisy environments. 0 ...
Page 28
... LTC2487 applicaTions inForMaTion Using the 2x speed mode of the LTC2487 alters the rejection characteristics around DC and multiples of f bypasses the offset calibration in order to increase the out- put rate. The resulting rejection plots are shown in Figures 26 and 27. 1x type frequency rejection can be achieved using the 2x mode by performing a running average of the previous two conversion results (see Figure 28) ...
Page 29
... RES = LOG 2 (V /INL RMS REF 100 OUTPUT DATA RATE (READINGS/SEC) 2487 F35 ≤ 1LSB) Figure 36. Resolution (INL RMS vs Output Data Rate and Temperature LTC2487 = 85° 25° 100 2487 F30 REF = 2.5V REF ...
Page 30
... Easy Drive also enables very low power, low bandwidth amplifiers to drive the input to the LTC2487. As shown in Figure 37, CH2 is driven by the LT1494. The LT1494 has excellent DC specs for an amplifier with 1.5µA supply current (the maximum offset voltage is 150µV and the open loop gain is 100,000) ...
Page 31
... TOP AND BOTTOM OF PACKAGE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC2487 R = 0.115 0.40 ± 0.10 TYP ...
Page 32
... Pin Compatible 16-Bit and 24-Bit Versions Pin Compatible 16-Bit and 24-Bit Versions Pin-Compatible 16-Bit and 24-Bit Versions Pin Compatible with LTC2487/LTC2493 Pin Compatible with LTC2487/LTC2489 Pin-Compatible 16-Bit and 24-Bit Versions Pin Compatible with LTC2449/LTC2494 LT/CGRAFX 0407 REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2007 ...