....... 5 V Single Supply, 8-Channel a 14-Bit 285 kSPS Sampling ADC AD7856 FUNCTIONAL BLOCK DIAGRAM FEATURES Single 5 V Supply AV AGND DD 285 kSPS Throughput Rate Self- and System Calibration with Autocalibration on DV Power-Up DD AIN1 I/P AD7856 T/H MUX Eight Single-Ended or Four Pseudo-Differential Inputs AIN8 Low Power: 60 mW Typ 4.096V Automatic Power-Down After Conversion (2.5 mW Typ) REFERENCE Flexible Serial Interface: 8051/SPI/QSPI/mP Compatible COMP 24-Lead DIP, SOIC and SSOP Packages DGND REF /REF BUF IN OUT APPLICATIONS C REF1 Battery-Powered Systems (Personal Digital Assistants, Medical Instruments, Mobile Communications) CHARGE REDISTRIBUTION Pen Computers DAC Instrumentation and Control Systems CLKIN High Speed Modems C SAR + ADC CONVST REF2 CONTROL CALIBRATION BUSY CAL MEMORY AND CONTROLLER SLEEP GENERAL DESCRIPTION SERIAL INTERFACE/CONTROL REGISTER The AD7856 is a high speed, low power, 14-bit ADC that oper- ates from a single 5 V power supply. The ADC powers up with SYNC DIN DOUT SCLK a set of default conditions at which time it can be operated as a read only ADC. The ADC contains self-calibration and system calibration options to ensure accurate operation over time and PRODUCT HIGHLIGHTS temperature and it has a number of power-down options for low 1. Single 5 V supply. power applications. 2. Automatic calibration on power-up. The AD7856 is capable of 285 kHz throughput rate. The input 3. Flexible power management options including automatic track-and-hold acquires a signal in 500 ns and features a pseudo- power-down after conversion. differential sampling scheme. The AD7856 voltage range is 0 to 4. Operates with reference voltages from 1.2 V to V . V with straight binary output coding. Input signal range is to DD REF the supply and the part is capable of converting full power sig- 5. Analog input range from 0 V to V . DD nals to 10 MHz. 6. Eight single-ended or four pseudo-differential input channels. CMOS construction ensures low power dissipation of typically 7. Self- and system calibration. 60 mW for normal operation and 5.1 mW in power-down mode at 10 kSPS throughput rate. The part is available in 24-lead, 8. Versatile serial I/O port (SPI/QSPI/8051/m P). 0.3 inch-wide dual in-line package (DIP), 24-lead small outline (SOIC) and 24-lead small shrink outline (SSOP) packages. Please see page 31 for data sheet index. SPI and QSPI are trademarks of Motorola, Inc. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: A Grade: f = 6 MHz, (408C to +1058C), f = 285 kHz K Grade: 1, 2 CLKIN SAMPLE AD7856SPECIFICATIONS f = 4 MHz, (08C to +1058C), f = 102 kHz (AV = DV = +5.0 V 6 5%, CLKIN SAMPLE DD DD REF /REF = 4.096 V External Reference unless otherwise noted, SLEEP = Logic High T = T to T , unless otherwise noted.) Specifica- IN OUT A MIN MAX tions apply for Mode 2 operation, standard 3-wire SPI interface refer to Detailed Timing section for Mode 1 Specifications. 1 1 Parameter A Version K Version Units Test Conditions/Comments DYNAMIC PERFORMANCE f = 10 kHz IN 3 Signal to Noise + Distortion Ratio (SNR) 78 78 dB min 79.5 dB typ Total Harmonic Distortion (THD) 86 86 dB max 95 dB typ Peak Harmonic or Spurious Noise 87 87 dB max 95 dB typ Intermodulation Distortion (IMD) Second Order Terms 86 90 dB typ fa = 9.983 kHz, fb = 10.05 kHz Third Order Terms 86 90 dB typ fa = 9.983 kHz, fb = 10.05 kHz Channel-to-Channel Isolation 90 90 dB typ V = 25 kHz IN DC ACCURACY Any Channel Resolution 14 14 Bits Integral Nonlinearity 2 LSB max 4.096 V External Reference, V = 5 V DD 2 LSB typ Differential Nonlinearity 2 LSB max Guaranteed No Missed Codes to 13 Bits. 2 LSB typ Offset Error 10 LSB max 10 5 LSB typ Offset Error Match 3 LSB max Positive Full-Scale Error 10 LSB max 10 LSB typ Positive Full-Scale Error Match 2 LSB max ANALOG INPUT Input Voltage Ranges 0 to V 0 to V Volts i.e., AIN(+) AIN() = 0 to V , AIN() Can Be REF REF REF Biased Up, but AIN(+) Cannot Go Below AIN() Leakage Current 1 1 m A max Input Capacitance 20 20 pF typ REFERENCE INPUT/OUTPUT REF Input Voltage Range 4.096/V 2.3/V V min/max Functional from 1.2 V IN DD DD Input Impedance 150 150 kW typ Resistor Connected to Internal Reference Node REF Output Voltage 3.696/4.496 3.696/4.496 V min/max OUT REF Tempco 20 20 ppm/ C typ OUT LOGIC INPUTS Input High Voltage, V V 1.0 V 1.0 V min INH DD DD Input Low Voltage, V 0.4 0.4 V max INL Input Current, I 1 1 m A max Typically 10 nA, V = 0 V or V IN IN DD 4 Input Capacitance, C 10 10 pF max IN LOGIC OUTPUTS Output High Voltage, V V 0.4 V 0.4 V min I = 200 m A OH DD DD SOURCE Output Low Voltage, V 0.4 0.4 V max I = 0.8 mA OL SINK Floating-State Leakage Current 1 1 m A max 4 Floating-State Output Capacitance 10 10 pF max Output Coding Straight (Natural) Binary CONVERSION RATE Conversion Time 3.5 5.25 m s max 21 CLKIN Cycles Track/Hold Acquisition Time 0.33 0.5 m s min 2 REV. A