5 V, 12-Bit, Serial 3.8 ms a ADC in 8-Pin Package AD7895 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast 12-Bit ADC with 3.8 ms Conversion Time REF IN V 8-Pin Mini-DlP and SOIC DD Single 5 V Supply Operation AD7895 High Speed, Easy-to-Use, Serial Interface On-Chip Track/Hold Amplifier Selection of Input Ranges TRACK/HOLD 610 V for AD7895-10 62.5 V for AD7895-3 SIGNAL V IN SCALING* 0 V to +2.5 V for AD7895-2 12-BIT ADC High Input Impedance Low Power: 20 mW max 14-Bit Pin Compatible Upgrade (AD7894) OUTPUT CONVST REGISTER GND BUSY SCLK SDATA *AD7895-10, AD7895-3 GENERAL DESCRIPTION The AD7895 is a fast 12-bit ADC that operates from a single +5 V supply and is housed in a small 8-pin mini-DIP and 8-pin SOIC. The part contains a 3.8 s successive approximation A/D PRODUCT HIGHLIGHTS converter, an on-chip track/hold amplifier, an on-chip clock and 1. Fast, 12-Bit ADC in 8-Pin Package a high speed serial interface. The AD7895 contains a 3.8 s ADC, a track/hold amplifier, control logic and a high speed serial interface, all in an 8-pin Output data from the AD7895 is provided via a high speed, package. This offers considerable space saving over alterna- serial interface port. This two-wire serial interface has a serial tive solutions. clock input and a serial data output with the external serial clock accessing the serial data from the part. 2. Low Power, Single Supply Operation The AD7895 operates from a single +5 V supply and In addition to the traditional dc accuracy specifications such as consumes only 20 mW. The automatic power-down mode, linearity and full-scale and offset errors, the AD7895 is specified where the part goes into power-down once conversion is for dynamic performance parameters, including harmonic complete and wakes up before the next conversion cycle, distortion and signal-to-noise ratio. makes the AD7895 ideal for battery-powered or portable The part accepts an analog input range of 10 V (AD7895-10), applications. 2.5 V (AD7895-3), 0 V to 2.5 V (AD7895-2) and operates 3. High Speed Serial Interface from a single +5 V supply, consuming only 20 mW max. The part provides high speed serial data and serial clock lines The AD7895 features a high sampling rate mode and, for low allowing for an easy, two-wire serial interface arrangement. power applications, a proprietary automatic power-down mode where the part automatically goes into power down once conversion is complete and wakes up before the next conver- sion cycle. The part is available in a small, 8-pin, 0.3 wide, plastic dual-in- line package (mini-DIP) and in an 8-pin, small outline IC (SOIC). REV. 0 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 Tel: 617/329-4700 World Wide Web Site: (V = +5 V, GND = 0 V, REF IN = +2.5 V. DD AD7895SPECIFICATIONS All specifications T to T unless otherwise noted) MIN MAX l Parameter A Versions B Versions Units Test Conditions/Comments 2 DYNAMIC PERFORMANCE 3 Signal to (Noise + Distortion) Ratio +25C 70 70 dB min f = 50 kHz Sine Wave, f = 200 kHz IN SAMPLE T to T 70 70 dB min MIN MAX 3 Total Harmonic Distortion (THD) 78 78 dB max f = 50 kHz Sine Wave, f = 200 kHz, IN SAMPLE Typically 87 dB 3 Peak Harmonic or Spurious Noise 89 89 dB typ f = 50 kHz Sine Wave, f = 200 kHz IN SAMPLE 3 Intermodulation Distortion (IMD) fa = 9 kHz, fb = 9.5 kHz, f = 200 kHz SAMPLE 2nd Order Terms 87 87 dB typ 3rd Order Terms 87 87 dB typ DC ACCURACY Resolution 12 12 Bits Minimum Resolution for which No Missing Codes are Guaranteed 12 12 Bits 3 Relative Accuracy 1 1 LSB max Typically 0.4 LSB 3 Differential Nonlinearity 1 1 LSB max 3 Positive Full-Scale Error 3 2 LSB max AD7895-2 Unipolar Offset Error 3 2 LSB max AD7895-10, AD7895-3 Only 3 Negative Full-Scale Error 3 2 LSB max Bipolar Zero Error 4 3 LSB max ANALOG INPUT AD7895-10 Input Voltage Range 10 10 Volts Input Resistance 24 24 k min AD7895-3 Input Voltage Range 2.5 2.5 Volts Input Resistance 9 9 k min AD7895-2 Input Voltage Range 0 to +2.5 0 to +2.5 Volts Input Current 500 500 nA max REFERENCE INPUT REF IN Input Voltage Range 2.375/2.625 2.375/2.625 V min/V max 2.5 V 5% Input Current 1 1 A max 3 Input Capacitance 10 10 pF max LOGIC INPUTS Input High Voltage, V 2.4 2.4 V min V = 5 V 5% INH DD Input Low Voltage, V 0.8 0.8 V max V = 5 V 5% INL DD Input Current, I 10 10 A max V = 0 V to V IN IN DD 4 Input Capacitance, C 10 10 pF ax IN LOGIC OUTPUTS Output High Voltage, V 4.0 4.0 V min I = 200 A OH SOURCE Output Low Voltage, V 0.4 0.4 V max I = 1.6 mA OL SINK Output Coding AD7895-10, AD7895-3 2s Complement AD7895-2 Straight (Natural) Binary CONVERSION RATE Conversion Time Mode 1 Operation 3.8 3.8 s max 5 Mode 2 Operation 9.8 9.8 s max 3 Track/Hold Acquisition Time 0.5 0.5 s max POWER REQUIREMENTS V +5 +5 V nom 5% for Specified Performance DD I 4 4 mA max Digital Inputs V , V = 5 V 5% DD DD DD Power Dissipation 20 20 mW max Typically 16 mW Power-Down Mode I +25C55 A max Digital Inputs GND, V = 5 V 5% DD DD T to T 10 10 A max Digital Inputs GND, V = 5 V 5% MIN MAX DD Power Dissipation +25C25 25 W max NOTES 1 Temperature ranges are as follows: A, B Versions: 40C to +85C. 2 Applies to Mode 1 operation. See section on Operating Modes. 3 See Terminology. 4 Sample tested +25C to ensure compliance. 5 This 9.8 s includes the wake-up time from standby. This wake-up time is timed from the rising edge of CONVST, whereas conversion is timed from the falling edge of CONVST, for narrow CONVST pulse width the conversion time is effectively the wake-up time plus conversion time hence 9.8 s. This can be seen from Figure 3. Note that if the CONVST pulse width is greater than 6 s then the effective conversion time will increase beyond 9.8 s. Specifications subject to change without notice. REV. 0 2