a 1 MSPS, Serial 14-Bit SAR ADC AD7485 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast Throughput Rate: 1 MSPS AV AGND C DV V DGND DD BIAS DD DRIVE Wide Input Bandwidth: 40 MHz Excellent DC Accuracy Performance Flexible Serial Interface 2.5 V Low Power: REFOUT BUF REFERENCE 80 mW (Full Power) and 3 mW (NAP Mode) REFSEL REFIN STANDBY Mode: 2 A Max Single 5 V Supply Operation 14-BIT Internal 2.5 V Reference ALGORITHMIC SAR VIN T/H Full-Scale Overrange Indication AD7485 GENERAL DESCRIPTION MCLK NAP The AD7485 is a 14-bit, high speed, low power, successive- TFS approximation ADC. The part features a serial interface with CONTROL STBY LOGIC AND I/O SCO throughput rates up to 1 MSPS. The part contains a low noise, REGISTERS RESET SDO wide bandwidth track-and-hold that can handle input frequencies CONVST in excess of 40 MHz. SMODE The conversion process is a proprietary algorithmic successive- approximation technique. The input signal is sampled and a conversion is initiated on the falling edge of the CONVST signal. The AD7485 features an on-board 2.5 V reference, but the part can The conversion process is controlled by an external master also accommodate an externally provided 2.5 V reference source. clock. Interfacing is via standard serial signal lines, making the The nominal analog input range is 0 V to 2.5 V. part directly compatible with microcontrollers and DSPs. The AD7485 also provides the user with overrange indication via a The AD7485 provides excellent ac and dc performance specifi- fifteenth bit. If the analog input range strays outside the 0 V to cations. Factory trimming ensures high dc accuracy resulting in 2.5 V input range, the fifteenth data bit is set to a logic high. very low INL, DNL, offset, and gain errors. The AD7485 is powered from a 4.75 V to 5.25 V supply. The The part uses advanced design techniques to achieve very low part also provides a V pin that allows the user to set the power dissipation at high throughput rates. Power consumption DRIVE voltage levels for the digital interface lines. The range for this in the normal mode of operation is 80 mW. There are two power- V pin is from 2.7 V to 5.25 V. The part is housed in a saving modes: a NAP mode keeps reference circuitry alive for DRIVE 48-lead LQFP package and is specified over a 40C to +85C quick power-up and consumes 3 mW, while a STANDBY mode temperature range. reduces power consumption to a mere 10 W. REV. 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 Fax: Analog Devices, Inc., under any patent or patent rights of Analog Devices.(V = 5 V 5%, AGND = DGND = 0 V, V = External, f = 1 MSPS all specifica- 1 DD REF SAMPLE AD7485SPECIFICATIONS tions T to T and valid for V = 2.7 V to 5.25 V, unless otherwise noted.) MIN MAX DRIVE Parameter Specification Unit Test Conditions/Comments 2, 3 DYNAMIC PERFORMANCE f = 500 kHz Sine Wave IN 4 Signal to Noise + Distortion (SINAD) 76.5 dB min 78 dB typ 77 dB typ Internal Reference 4 Total Harmonic Distortion (THD) 90 dB max 95 dB typ 92 dB typ Internal Reference 4 Peak Harmonic or Spurious Noise (SFDR) 88 dB max 4 Intermodulation Distortion (IMD) Second-Order Terms 96 dB typ f = 95.053 kHz, f = 105.329 kHz IN1 IN2 Third-Order Terms 94 dB typ Aperture Delay 10 ns typ Full Power Bandwidth 40 MHz typ 3 dB 3.5 MHz typ 0.1 dB DC ACCURACY Resolution 14 Bits 4 Integral Nonlinearity 1LSB max 0.5 LSB typ 4 Differential Nonlinearity 0.75 LSB max Guaranteed No Missed Codes to 14 Bits 0.25 LSB typ 4 Offset Error 6LSB max 0.036 %FSR max 4 Gain Error 6LSB max 0.036 %FSR max ANALOG INPUT Input Voltage 0 V min 2.5 V max DC Leakage Current 1 A max 5 Input Capacitance 35 pF typ REFERENCE INPUT/OUTPUT V Input Voltage 2.5 V 1% for Specified Performance REFIN V Input DC Leakage Current 1 A max REFIN 5 V Input Capacitance 25 pF typ REFIN 6 V Input Current 220 A typ External Reference REFIN V Output Voltage 2.5 V typ REFOUT V Error 25C 50 mV typ REFOUT V Error T to T 100 mV max REFOUT MIN MAX V Output Impedance 1 typ REFOUT LOGIC INPUTS Input High Voltage, V V 1V min INH DRIVE Input Low Voltage, V 0.4 V max INL Input Current, I 1 A max IN 5 Input Capacitance, C 10 pF typ IN LOGIC OUTPUTS 7 Output High Voltage, V 0.7 V V min OH DRIVE 7 Output Low Voltage, V 0.3 V V max OL DRIVE Floating-State Leakage Current 10 A max 5 Floating-State Output Capacitance 10 pF max Output Coding Straight (Natural) Binary CONVERSION RATE Conversion Time 24 MCLKs Track/Hold Acquisition Time 100 ns max Sine Wave Input 70 ns max Full-Scale Step Input Throughput Rate 1 MSPS max 2 REV.