AD7821KRZ

2 LC MOS High Speed, P Compatible a 8-Bit ADC with Track/Hold Function AD7821 FUNCTIONAL BLOCK DIAGRAM FEATURES Fast Conversion Time: 660 ns Max 100 kHz Track-and-Hold Function 1 MHz Sample Rate Unipolar and Bipolar Input Ranges Ratiometric Reference Inputs No External Clock Extended Temperature Range Operation Skinny 20-Lead DlPs, SOIC, and 20-Terminal Surface-Mount Packages GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7821 is a high speed, 8-bit, sampling, analog-to-digital 1. Fast Conversion Time converter that offers improved performance over the popular The half-flash conversion technique, coupled with fabrication 2 AD7820. It offers a conversion time of 660 ns (versus 1.36 s on Analog Devices LC MOS process, enables a very fast con- for the AD7820) and 100 kHz signal bandwidth (versus 6.4 version time. The conversion time for the WR-RD mode is kHz). The sampling instant is better defined and occurs on the 660 ns, with 700 ns for the RD mode. falling edge of WR or RD. The provision of a V pin (Pin 19) SS 2. Built-In Track-and-Hold allows the part to operate from 5 V supplies and to digitize This allows input signals with slew rates up to 1.6 V/s to be bipolar input signals. Alternatively, for unipolar inputs, the V pin SS converted to 8 bits without an external track-and-hold. This can be grounded and the AD7821 will operate from a single +5 V corresponds to a 5 V peak-to-peak, 100 kHz sine wave signal. supply, like the AD7820. 3. Total Unadjusted Error The AD7821 has a built-in track-and-hold function capable of The AD7821 features an excellent total unadjusted error figure digitizing full-scale signals up to 100 kHz max. It also uses a of less than 1 LSB over the full operating temperature range. half-flash conversion technique that eliminates the need to gen- 4. Unipolar/Bipolar Input Ranges erate a CLK signal for the ADC. The AD7821 is specified for single-supply (+5 V) operation The AD7821 is designed with standard microprocessor control with a unipolar full-scale range of 0 to +5 V, and for dual-supply signals (CS, RD, WR, RDY, INT) and latched, three-state data (5 V) operation with a bipolar input range of 2.5 V. Typical outputs capable of interfacing to high speed data buses. An performance characteristics are given for other input ranges. overflow output (OFL) is also provided for cascading devices to 5. Dynamic Specifications for DSP Users achieve higher resolution. In addition to the traditional ADC specifications, the The AD7821 is fabricated in Linear Compatible CMOS AD7821 is specified for ac parameters, including signal-to- 2 (LC MOS), an advanced, mixed technology process combining noise ratio, distortion, and slew rate. precision bipolar circuits with low power CMOS logic. The part features a low power dissipation of 50 mW. REV. B 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 that Tel: 781/329-4700 www.analog.com may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 Analog Devices, Inc., 2002V = +5 V 5%, GND = 0 V. Unipolar Input Range: V = GND, V (+) = 5 V, DD SS REF AD7821SPECIFICATIONS V () = GND. Bipolar Input Range: V = 5 V 5%, V (+) = 2.5 V, REF SS REF V () = 2.5 V. These test conditions apply unless otherwise stated. All specifications T to T unless otherwise noted. Specifications REF MIN MAX apply for RD Mode (Pin 7 = 0 V). 1 Parameter K Version B, T Versions Unit Comments UNIPOLAR INPUT RANGE 2 Resolution 88 Bits 3 Total Unadjusted Error 1 1 LSB max Minimum Resolution for which No Missing Codes are Guaranteed 8 8 Bits BIPOLAR INPUT RANGE 2 Resolution 88 Bits Zero Code Error 1 1 LSB max Full Scale Error 1 1 LSB max 3 Signal-to-Noise Ratio (SNR) 45 45 dB min V = 99.85 kHz Full-Scale Sine Wave with f = 500 kHz IN SAMPLING 3 Total Harmonic Distortion (THD) 50 50 dB max V = 99.85 kHz Full-Scale Sine Wave with f = 500 kHz IN SAMPLING 3 Peak Harmonic or Spurious Noise 50 50 dB max V = 99.85 kHz Full-Scale Sine Wave with f = 500 kHz IN SAMPLING 3 Intermodulation Distortion (IMD) fa (84.72 kHz) and fb (94.97 kHz) Full-Scale Sine Waves with f = 500 kHz SAMPLING 50 50 dB max Second Order Terms 50 50 dB max Third Order Terms 3 Slew Rate, Tracking 1.6 1.6 V/s max 2.36 2.36 V/s typ REFERENCE INPUT Input Resistance 1.0/4.0 1.0/4.0 k min/k max V (+) Input Voltage Range V ()/V V ()/V V min/V max REF REF DD REF DD V () Input Voltage Range V /V (+) V /V (+) V min/V max REF SS REF SS REF ANALOG INPUT Input Voltage Range V ()/V (+) V ()/V (+) V min/ max REF REF REF REF Input Leakage Current 3 3 A max 5 V V +5 V IN Input Capacitance 55 55 pF typ LOGIC INPUTS CS, WR, RD V 2.4 2.4 V min INH V 0.8 0.8 V max INL I (CS, RD)1 1 A max INH I (WR)3 3 A max INH I 1 1 A max INL 4 Input Capacitance 88 pF max Typically 5 pF MODE V 3.5 3.5 V min INH V 1.5 1.5 V max INL I 200 200 A max 50 A typ INH I 1 1 A max INL 4 Input Capacitance 88 pF max Typically 5 pF LOGIC OUTPUTS DB0DB7, OFL, INT V 4.0 4.0 V min I = 360 A OH SOURCE V 0.4 0.4 V max I = 1.6 mA OL SINK I (DB0DB7) 3 3 A max Floating State Leakage OUT 4 Output Capacitance (DB0DB7) 8 8 pF max Typically 5 pF RDY V 0.4 0.4 V max I = 2.6 mA OL SINK I 3 3 A max Floating State Leakage OUT 4 Output Capacitance 88 pF max Typically 5 pF POWER SUPPLY 5 I 20 20 mA max CS = RD = 0 V DD I 100 100 A max CS = RD = 0 V SS Power Dissipation 50 50 mW typ Power Supply Sensitivity 1/4 1/4 LSB max 1/16 LSB typ, V = 4.75 V to 5.25 V, DD (V (+) = 4.75 V max for Unipolar Mode) REF NOTES 1 Temperature Ranges are as follows: K Version = 40C to +85C B Version = 40C to +85C T Version = 55C to +125C. 2 1 LSB = 19.53 mV for both the unipolar (0 V to +5 V) and bipolar (2.5 V to +2.5 V) input ranges. 3 See Terminology. 4 Sample tested at +25C to ensure compliance. 5 See Typical Performance Characteristics. Specifications subject to change without notice. 2 REV. B