16-Bit, Low-Power, 2-Channel, MX7705 Sigma-Delta ADC General Description Benefits and Features The MX7705 low-power, 2-channel, serial-output ana- Pin Compatible and Software Compatible with the log-to-digital converter (ADC) includes a sigma-delta AD7705 modulator with a digital filter to achieve 16-bit resolution 16-Bit Sigma-Delta ADC with no missing codes. This ADC is pin compatible and Two Fully Differential Input Channels software compatible with the AD7705. The MX7705 fea- 0.003% Integral Nonlinearity with No Missing Codes tures an on-chip input buffer and programmable-gain amplifier (PGA). The device offers an SPI-/QSPI -/ Interface with Schmitt Triggers on Inputs MICROWIRE-compatible serial interface. Internal Analog Input Buffers The MX7705 operates from a single 2.7V to 5.25V supply. PGA from 1 to 128 The operating supply current is 320A (typ) with a 3V Single (2.7V to 3.6V) or (4.75V to 5.25V) Supply supply. Power-down mode reduces the supply current to Low Power 2A (typ). 1mW (max), 3V Supply Self-calibration and system calibration allow the MX7705 2A (typ) Power-Down Current to correct for gain and offset errors. Excellent DC perfor- mance (0.003% FSR INL) and low noise (650nV) make SPI-/QSPI-/MICROWIRE-Compatible 3-Wire Serial the MX7705 ideal for measuring low-frequency signals Interface with a wide dynamic range. The device accepts fully dif- ferential bipolar/unipolar inputs. An internal input buffer allows for input signals with high source impedances. An Ordering Information on-chip digital filter, with a programmable cutoff and out- put data rate, processes the output of the sigma-delta PART TEMP RANGE PIN- PACKAGE modulator. The first notch frequency of the digital filter is MX7705EPE+ -40C to +85C 16 PDIP chosen to provide 150dB rejection of common-mode MX7705EUE+ -40C to +85C 16 TSSOP 50Hz or 60Hz noise and 98dB rejection of normal-mode 50Hz or 60Hz noise. A PGA and digital filtering allow sig- MX7705EWE+ -40C to +85C 16 SO nals to be directly acquired with little or no signal-condi- +Denotes a lead(Pb)-free/RoHS-compliant package. tioning requirements. The MX7705 is available in a 16-pin TSSOP package. Applications Pin Configuration Industrial Instruments Weigh Scales TOP VIEW Strain-Gauge Measurements SCLK 1 16 GND Loop-Powered Systems CLKIN 2 15 V DD Flow and Gas Meters CLKOUT 3 14 DIN Medical Instrumentation MX7705 CS 4 13 DOUT Pressure Transducers RESET 5 12 DRDY Thermocouple Measurements AIN2+ 6 11 AIN2- RTD Measurements AIN1+ 7 10 REF- AIN1- 8 9 REF+ TSSOP QSPI is a trademark of Motorola, Inc. MICROWIRE is a registered trademark of National Semiconductor Corp. 19-3051 Rev 5 6/1516-Bit, Low-Power, 2-Channel, MX7705 Sigma-Delta ADC Absolute Maximum Ratings V to GND..............................................................-0.3V to +6V Operating Temperature Range ..........................-40C to +85C DD All Other Pins to GND.................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-60C to +150C DD Maximum Current Input into Any Pin ..................................50mA Junction Temperature......................................................+150C Continuous Power Dissipation (T = +70C) Lead Temperature (soldering, 10s) .................................+300C A TSSOP (derate 9.4mW/C above +70C) ...................755mW Soldering Temperature (reflow) .......................................+260C SO (derate 9.5mW/C above +70C).......................761.9mW PDIP (derate 10.5mW/C above +70C)..................842.1mW Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (V = 3V or 5V, V = 0V, V = 1.225V for V = 3V and V = 2.5V for V = 5V, V = GND, external f = + - DD GND REF DD REF+ DD REF CLKIN 2.4576MHz, CLKDIV bit = 0, C to GND = 0.1F, C - to GND = 0.1F, T = T to T , unless otherwise noted.) + REF REF A MIN MAX PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY Resolution (No Missing Codes) 16 Bits Output Noise Tables 1, 3 V Integral Nonlinearity INL Gain = 1, unbuffered 0.003 %FSR Unipolar Offset Error After calibration (Note 1) V Unipolar Offset Drift (Note 2) 0.5 V/C Bipolar Zero Error After calibration (Note 1) V Gain = 1 to 4 0.5 Bipolar Zero Drift (Note 2) V/C Gain = 8 to 128 0.1 Positive Full-Scale Error After calibration (Notes 1, 3) V Full-Scale Drift (Notes 2, 4) 0.5 V/C Gain Error After calibration (Notes 1, 5) V ppm of Gain Drift (Notes 2, 6) 0.5 FSR/C Bipolar Negative Full-Scale Error After calibration 0.003 %FSR Gain = 1 to 4 1 Bipolar Negative Full-Scale Drift V/C (Note 2) Gain = 8 to 128 0.6 ANALOG INPUTS (AIN1+, AIN1-, AIN2+, AIN2-) V / REF Unipolar input range 0 GAIN AIN Differential Input Voltage V Range (Note 7) -V / V / REF REF Bipolar input range GAIN GAIN GND - V + DD Unbuffered 30mV 30mV AIN Absolute Input Voltage V Range (Note 8) GND + V - DD Buffered 50mV 1.5V AIN DC Leakage Current Unselected input channel 1 nA www.maximintegrated.com Maxim Integrated 2