5 V, 14-Bit Serial, 5 ms a ADC in SO-8 Package AD7894 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast 14-Bit ADC with 5 ms Conversion Time V 8-Lead SOIC Package REF IN DD Single 5 V Supply Operation AD7894 High Speed, Easy-to-Use, Serial Interface On-Chip Track/Hold Amplifier Selection of Input Ranges TRACK/ HOLD SIGNAL 610 V for AD7894-10 V IN SCALING* 14-BIT 62.5 V for AD7894-3 ADC 0 V to +2.5 V for AD7894-2 High Input Impedance Low Power: 20 mW Typ OUTPUT CONVST REGISTER Pin Compatible Upgrade of 12-Bit AD7895 GND BUSY SCLK SDATA *AD7894-10, AD7894-3 GENERAL DESCRIPTION The AD7894 is a fast, 14-bit ADC that operates from a single PRODUCT HIGHLIGHTS +5 V supply and is housed in a small 8-lead SOIC. The part 1. Fast, 14-Bit ADC in 8-Lead Package contains a 5 m s successive approximation A/D converter, an on- The AD7894 contains a 5 m s ADC, a track/hold amplifier, chip track/hold amplifier, an on-chip clock and a high speed control logic and a high speed serial interface, all in an 8-lead serial interface. package. This offers considerable space saving over alterna- Output data from the AD7894 is provided via a high speed, tive solutions. serial interface port. This two-wire serial interface has a serial 2. Low Power, Single Supply Operation clock input and a serial data output with the external serial clock The AD7894 operates from a single +5 V supply and con- accessing the serial data from the part. sumes only 20 mW. The automatic power-down mode, In addition to the traditional dc accuracy specifications such as where the part goes into power-down once conversion is linearity, full-scale and offset errors, the AD7894 is also speci- complete and wakes up before the next conversion cycle, fied for dynamic performance parameters including harmonic makes the AD7894 ideal for battery powered or portable distortion and signal-to-noise ratio. applications. The part accepts an analog input range of 10 V (AD7894-10), 3. High Speed Serial Interface 2.5 V (AD7894-3), 0 V to +2.5 V (AD7894-2), and operates The part provides high speed serial data and serial clock lines from a single +5 V supply consuming only 20 mW typical. allowing for an easy, two-wire serial interface arrangement. The AD7894 features a high sampling rate mode and, for low power applications, a proprietary automatic power-down mode where the part automatically goes into power-down once conver- sion is complete and wakes up before the next conversion cycle. The part is available in a 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 which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: (V = +5 V 6 5%, GND = 0 V, REF IN = +2.5 V. All specifications T to T unless DD MIN MAX otherwise noted.) AD7894SPECIFICATIONS l 1 Parameter A Versions B Versions Units Test Conditions/Comments 2 DYNAMIC PERFORMANCE 3 Signal to (Noise + Distortion) Ratio +25 C 78 78 dB min f = 70 kHz Sine Wave, f = 160 kHz IN SAMPLE T to T 77 77 dB min See Figure 14 MIN MAX 3 Total Harmonic Distortion (THD) 86 86 dB max f = 10 kHz Sine Wave, f = 160 kHz, IN SAMPLE Typically 87 dB. See Figure 15 3 Peak Harmonic or Spurious Noise 92 92 dB typ f = 10 kHz Sine Wave, f = 160 kHz IN SAMPLE 3 Intermodulation Distortion (IMD) fa = 9 kHz, fb = 9.5 kHz, f = 160 kHz SAMPLE 2nd Order Terms 92 92 dB typ 3rd Order Terms 92 92 dB typ DC ACCURACY Resolution 14 14 Bits Minimum Resolution for Which No Missing Codes Are Guaranteed 14 14 Bits 3 Relative Accuracy 2 1.5 LSB max 3 Differential Nonlinearity 1 to +1.5 1 to +1.5 LSB max AD7894-2 3 Positive Gain Error 12 10 LSB max Unipolar Offset Error 8 6 LSB max AD7894-10, AD7894-3 Only 3 Positive Gain Error 8 6 LSB max 3 Negative Gain Error 8 6 LSB max Bipolar Zero Error 10 8 LSB max ANALOG INPUT AD7894-10 Input Voltage Range 10 10 V Input Current 2 2 mA max See Analog Input Section AD7894-3 Input Voltage Range 2.5 2.5 V Input Current 1.5 1.5 mA max See Analog Input Section AD7894-2 Input Voltage Range 0 to +2.5 0 to +2.5 V 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 m A max 4 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 m A max V = 0 V to V IN IN DD 4 Input Capacitance, C 10 10 pF max IN LOGIC OUTPUTS Output High Voltage, V 4.0 4.0 V min I = 400 m A OH SOURCE Output Low Voltage, V 0.4 0.4 V max I = 1.6 mA OL SINK Output Coding AD7894-10, AD7894-3 Twos Complement AD7894-2 Straight (Natural) Binary CONVERSION RATE Conversion Time Mode 1 Operation 5 5 m s max 5 Mode 2 Operation 10 10 m s max 3 Track/Hold Acquisition Time 0.35 0.35 m s max SAMPLE AND HOLD 3 dB Small Signal Bandwidth 7.5 7.5 MHz typ Aperture Jitter 50 50 ps typ 2 REV. 0