LTC2446/LTC2447 24-Bit High Speed 8-Channel ADCs with Selectable Multiple Reference Inputs FEATURES DESCRIPTION n Five Selectable Differential Reference Inputs The LTC 2446/LTC2447 4-terminal switching enables n Four Differential/Eight Single-Ended Inputs multiplexed ratiometric measurements. Four sets of n 4-Way MUX for Multiple Ratiometric selectable differential inputs coupled with four sets of Measurements differential reference inputs allow multiple RTDs, bridges n Up to 8kHz Output Rate (External f ) O and other sensors to be digitized by a single converter. n Up to 4kHz Multiplexing Rate (External f ) O A fifth differential reference input can be selected for any n Selectable Speed/Resolution: input channel not requiring ratiometric measurements 2V Noise at 1.76kHz Output Rate RMS (thermocouples, voltages, current sense, etc.). The flex- 200nV Noise at 13.8Hz Output Rate with RMS ible input multiplexer allows single-ended or differential Simultaneous 50/60Hz Rejection inputs coupled with a slaved reference input or a universal n Guaranteed Modulator Stability and Lock-Up reference input. Immunity for any Input and Reference Conditions n 0.0005% INL, No Missing Codes A proprietary delta-sigma architecture results in absolute n Autosleep Enables 20A Operation at 6.9Hz accuracy (offset, full-scale, linearity) of 15ppm, noise as n <5V Offset (4.5V < V < 5.5V, 40C to 85C) CC low as 200nV and speeds as high as 8kHz. Through RMS n Differential Input and Differential Reference with a simple 4-wire interface, ten speed/resolution combina- GND to V Common Mode Range CC tions can be selected. The first conversion following a n No Latency Mode, Each Conversion is Accurate Even speed, resolution, channel change or reference change is After a New Channel is Selected valid since there is no settling time between conversions, n Internal OscillatorNo External Components n enabling scan rates of up to 4kHz. Additionally, a 2 mode LTC2447 Includes MUXOUT/ADCIN for External can be selected for any speed-enabling output rates up to Buffering or Gain n Tiny QFN 5mm 7mm Package 8kHz with one cycle of latency. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. APPLICATIONS Protected by U.S. patents, including 6140950, 6169506, 6208279, 6411242, 6639526. n Flow n Weight Scales n Pressure n Direct Temperature Measurement n Gas Chromatography TYPICAL APPLICATION LTC2446 RMS Noise vs Speed 100 Multiple Ratiometric Measurement System V = 5V CC V = 5V REF + V = V = 0V IN IN 2 SPEED MODE V LTC2446 CC NO LATENCY MODE + 10 REF 2.8V AT 880Hz + CS IN 280nV AT 6.9Hz + 19-INPUT SDI VARIABLE SPEED/ (50/60Hz REJECTION) 1 4-OUTPUT RESOLUTION 24-BIT SDO MUX IN ADC SCK REF 0.1 1 10 100 1000 10000 CONVERSION RATE (Hz) 24467 TA01 24467 TA02 24467fb 1 For more information www.linear.com/LTC2446 RMS NOISE (V)LTC2446/LTC2447 ABSOLUTE MAXIMUM RATINGS Supply Voltage (V ) to GND ....................... 0.3V to 6V Digital Output Voltage to GND .......0.3V to (V + 0.3V) CC CC Analog Input Pins Voltage Operating Temperature Range to GND ......................................0.3V to (V + 0.3V) LTC2446C/LTC2447C .............................. 0C to 70C CC Reference Input Pins Voltage LTC2446I/LTC2447I ............................40C to 85C to GND ......................................0.3V to (V + 0.3V) Storage Temperature Range .................. 65C to 125C CC Digital Input Voltage to GND .........0.3V to (V + 0.3V) CC PIN CONFIGURATION LTC2446 LTC2447 TOP VIEW TOP VIEW 38 37 36 35 34 33 32 38 37 36 35 34 33 32 GND 1 31 GND GND 1 31 GND BUSY 2 30 REFG BUSY 2 30 REFG + + EXT 3 29 REFG EXT 3 29 REFG GND 4 28 V GND 4 28 V CC CC GND 5 27 NC GND 5 27 MUXOUTN GND NC GND ADCINN 6 26 6 26 39 39 COM 7 25 NC COM 7 25 ADCINP CH0 8 24 NC CH0 8 24 MUXOUTP + + CH1 9 23 V CH1 9 23 V REF67 REF67 V 10 22 V V 10 22 V REF01 REF67 REF01 REF67 + + V 11 21 CH7 V 11 21 CH7 REF01 REF01 20 20 CH2 12 CH6 CH2 12 CH6 13 14 15 16 17 18 19 13 14 15 16 17 18 19 UHF PACKAGE UHF PACKAGE 38-LEAD (5mm 7mm) PLASTIC QFN 38-LEAD (5mm 7mm) PLASTIC QFN T = 125C, = 34C/W T = 125C, = 34C/W JMAX JA JMAX JA EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION