Simultaneous Sampling a Dual 250 kSPS 12-Bit ADC AD7862 FEATURES FUNCTIONAL BLOCK DIAGRAM Two Fast 12-Bit ADCs V V REF DD Four Input Channels Simultaneous Sampling & Conversion +2.5V REFERENCE 2k 4 ms Throughput Time AD7862 Single Supply Operation Selection of Input Ranges: 610 V for AD7862-10 SIGNAL TRACK/ V A1 SCALING 62.5 V for AD7862-3 HOLD MUX 12-BIT SIGNAL 0 V to 2.5 V for AD7862-2 ADC V B1 DB0 SCALING High Speed Parallel Interface OUTPUT SIGNAL LATCH V DB11 A2 Low Power, 60 mW typ SCALING TRACK/ MUX HOLD 12-BIT Power Saving Mode, 50 mW typ SIGNAL V B2 SCALING ADC Overvoltage Protection on Analog Inputs 14-Bit Pin Compatible Upgrade (AD7863) CS CONVERSION CLOCK RD CONTROL LOGIC APPLICATIONS AC Motor Control Uninterrupted Power Supplies A0 BUSY CONVST AGND AGND DGND Data Acquisition Systems Communications GENERAL DESCRIPTION The AD7862 is fabricated in Analog Devices Linear Compat- 2 The AD7862 is a high speed, low power, dual 12-bit A/D ible CMOS (LC MOS) process, a mixed technology process converter that operates from a single +5 V supply. The part that combines precision bipolar circuits with low power CMOS contains two 4 s successive approximation ADCs, two track/ logic. It is available in 28-lead SSOP, SOIC and DIP. hold amplifiers, an internal +2.5 V reference and a high speed parallel interface. There are four analog inputs that are grouped PRODUCT HIGHLIGHTS into two channels (A & B) selected by the A0 input. Each 1. The AD7862 features two complete ADC functions allowing channel has two inputs (V & V or V & V ) that can be simultaneous sampling and conversion of two channels. Each A1 A2 B1 B2 sampled and converted simultaneously thus preserving the ADC has a 2-channel input mux. The conversion result for relative phase information of the signals on both analog inputs. both channels is available 3.6 s after initiating conversion. The part accepts an analog input range of 10 V (AD7862-10), 2. The AD7862 operates from a single +5 V supply and 2.5 V (AD7862-3) and 02.5 V (AD7862-2). Overvoltage consumes 60 mW typ. The automatic power-down mode, protection on the analog inputs for the part allows the input where the part goes into power down once conversion is voltage to go to 17 V, 7 V or +7 V, respectively, without complete and wakes up before the next conversion cycle, causing damage. makes the AD7862 ideal for battery-powered or portable A single conversion start signal (CONVST) places both track/ applications. holds into hold simultaneously and initiates conversion on both 3. The part offers a high speed parallel interface for easy con- inputs. The BUSY signal indicates the end of conversion, and nection to microprocessors, microcontrollers and digital at this time the conversion results for both channels are avail- signal processors. able to be read. The first read after a conversion accesses the 4. The part is offered in three versions with different analog result from V or V , while the second read accesses the result A1 B1 input ranges. The AD7862-10 offers the standard industrial from V or V , depending on whether the multiplexer select A2 B2 input range of 10 V the AD7862-3 offers the common A0 is low or high, respectively. Data is read from the part via a signal processing input range of 2.5 V while the AD7862-2 12-bit parallel data bus with standard CS and RD signals. can be used in unipolar 0 V +2.5 V applications. In addition to the traditional dc accuracy specifications such as 5. The part features very tight aperture delay matching between linearity, full-scale and offset errors, the part is also specified for the two input sample-and-hold amplifiers. dynamic performance parameters including harmonic distortion and signal-to-noise ratio. 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 6 5%, AGND = DGND = 0 V, REF = Internal. All Specifications T to T DD MIN MAX AD7862SPECIFICATIONS unless otherwise noted.) AB S 1 Parameter Version Version Version Units Test Conditions/Comments SAMPLE AND HOLD 3 dB Small Signal Bandwidth 3 3 3 MHz typ Aperture Delay 20 20 20 ns typ Aperture Jitter 100 100 100 ps typ Aperture Delay Matching 200 200 200 ps typ 2 DYNAMIC PERFORMANCE f = 100.0 kHz, f = 250 kSPS IN S 3 Signal to (Noise+Distortion) Ratio +25C 70 71 70 dB min T to T 70 70 70 dB min MIN MAX 3 Total Harmonic Distortion 78 78 78 dB max 3 Peak Harmonic or Spurious Noise 85 85 85 dB typ 3 Intermodulation Distortion fa = 49 kHz, fb = 50 kHz 2nd Order Terms 85 85 85 dB typ 3rd Order Terms 85 85 85 dB typ 3 Channel to Channel Isolation 80 80 80 dB max f = 100 kHz Sine Wave IN DC ACCURACY Any Channel Resolution 12 12 12 Bits Minimum Resolution for which No Missing Codes are Guaranteed 12 12 12 Bits 3 Relative Accuracy 1 1 1 LSB max Typically 0.4 LSB 3 Differential Nonlinearity 1 1 1 LSB max 3 Positive Gain Error 4 3 4 LSB max 3 Positive Gain Error Match 4 3 4 LSB max AD7862-10 3 Negative Gain Error 4 3 4 LSB max Bipolar Zero Error 4 3 4 LSB max Bipolar Zero Error Match 4 3 4 LSB max AD7862-3 3 Negative Gain Error 4 3 4 LSB max Bipolar Zero Error 4 3 4 LSB max Bipolar Zero Error Match 4 3 4 LSB max AD7862-2 Unipolar Offset Error +4 +3 +4 LSB max Unipolar Offset Error Match 4 3.5 4 LSB max ANALOG INPUTS AD7862-10 Input Voltage Range 10 10 10 Volts Input Input Resistance 24 24 24 k min AD7862-3 Input Voltage Range 2.5 2.5 2.5 Volts Input Input Resistance 6 6 6 k min AD7862-2 Input Voltage Range +2.5 +2.5 +2.5 Volts Input Input Current 500 500 500 nA max REFERENCE INPUT/OUTPUT REF IN Input Voltage Range 2.375/2.625 2.375/2.625 2.375/2.625 V min/V max 2.5 V 5% 4 REF IN Input Capacitance 10 10 10 pF max REF OUT Output Voltage 2.5 2.5 2.5 V nom REF OUT Error +25C 10 10 10 mV max to T 25 25 25 mV max REF OUT Error T MIN MAX REF OUT Temperature Coefficient 25 25 25 ppm/C typ REF OUT Output Impedance 2 2 2 k nom LOGIC INPUTS Input High Voltage, V 2.4 2.4 2.4 V min V = 5 V 5% INH DD Input Low Voltage, V 0.8 0.8 0.8 V max V = 5 V 5% INL DD Input Current, I 10 10 10 A max IN 4 Input Capacitance, C 10 10 10 pF max IN REV. 0 2