Low Power, Pseudo Differential, 100 kSPS 12-Bit ADC in an 8-Lead SOT-23 AD7457 FEATURES FUNCTIONAL BLOCK DIAGRAM V Specified for VDD of 2.7 V to 5.25 V DD Low power: 0.9 mW max at 100 kSPS with V = 3 V DD 3 mW max at 100 kSPS with VDD = 5 V Pseudo differential analog input V 12-BIT IN+ T/H SUCCESSIVE Wide input bandwidth: APPROXIMATION V IN ADC 70 dB SINAD at 30 kHz input frequency V REF Flexible power/serial clock speed management No pipeline delays High speed serial interfaceSPI-/QSPI-/ SCLK MICROWIRE-/DSP-compatible SDATA Automatic power-down mode AD7457 CONTROL LOGIC CS 8-lead SOT-23 package APPLICATIONS Transducer interface GND Battery-powered systems Data acquisition systems Figure 1. Portable instrumentation GENERAL DESCRIPTION PRODUCT HIGHLIGHTS 1. Operation with 2.7 V to 5.25 V power supplies. The AD7457 is a 12-bit, low power, successive approximation 2. Low power consumption. With a 3 V supply, the AD7457 (SAR) analog-to-digital converter that features a pseudo offers 0.9 mW maximum power consumption for a differential analog input. This part operates from a single 2.7 V 100 kSPS throughput rate. to 5.25 V power supply and features throughput rates of up to 3. Pseudo differential analog input. 100 kSPS. 4. Flexible power/serial clock speed management. The The part contains a low noise, wide bandwidth, differential conversion rate is determined by the serial clock, allowing track-and-hold (T/H) amplifier that can handle input frequen- the power to be reduced as the conversion time is reduced cies in excess of 1 MHz. The reference voltage for the AD7457 is through the serial clock speed increase. Automatic power- applied externally to the V pin and can range from 100 mV to REF down after conversion allows the average power consump- VDD, depending on what suits the application. tion to be reduced. 5. Variable voltage reference input. The conversion process and data acquisition are controlled 6. No pipeline delays. using CS and the serial clock, allowing the device to interface CS 7. Accurate control of the sampling instant via the input with microprocessors or DSPs. The SAR architecture of this and once-off conversion control. part ensures that there are no pipeline delays. 8. ENOB > 10 bits typically with 500 mV reference. The AD7457 uses advanced design techniques to achieve very low power dissipation. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Specifications subject to change without notice. No license is granted by implication Tel: 781.329.4700 www.analog.com or otherwise under any patent or patent rights of Analog Devices. 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All rights reserved. 03157-0-013AD7457 TABLE OF CONTENTS Specifications..................................................................................... 3 Analog Input ............................................................................... 12 Timing Specifications....................................................................... 5 Analog Input Structure.............................................................. 12 Absolute Maximum Ratings............................................................ 6 Digital Inputs .............................................................................. 13 ESD Caution.................................................................................. 6 Reference Section ....................................................................... 13 Pin Configuration and Function Descriptions............................. 7 Serial Interface ............................................................................ 13 Typical Performance Characteristics ............................................. 8 Power Consumption .................................................................. 14 Terminology .................................................................................... 10 Microprocessor Interfacing....................................................... 14 Theory of Operation ...................................................................... 11 Application Hints ........................................................................... 16 Circuit Information.................................................................... 11 Grounding and Layout .............................................................. 16 Converter Operation.................................................................. 11 Outline Dimensions ....................................................................... 17 ADC Transfer Function............................................................. 11 Ordering Guide .......................................................................... 17 Typical Connection Diagram ................................................... 11 REVISION HISTORY 2/05Rev. 0 to Rev. A Changes to Table 3............................................................................ 6 Changes to Ordering Guide .......................................................... 17 10/03Rev. 0: Initial Version Rev. A Page 2 of 20