Datasheet AD7938-6 (Analog Devices)

8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer Data Sheet AD7938-6 FEATURES FUNCTIONAL BLOCK DIAGRAM Throughput rate: 625 kSPS VDD AGND Specified for VDD of 2.7 V to 5.25 V V AD7938-6 Power consumption REFIN/ VREFOUT 3.6 mW maximum at 625 kSPS with 3 V supplies 2.5V VREF 7.5 mW maximum at 625 kSPS with 5 V supplies VIN0 CLKIN 8 analog input channels with a sequencer 12-BIT I/P SAR ADC T/H CONVST Software-configurable analog inputs MUX AND CONTROL BUSY 8-channel single-ended inputs VIN7 4-channel fully differential inputs 4-channel pseudo differential inputs SEQUENCER 7-channel pseudo differential inputs Accurate on-chip 2.5 V reference PARALLEL INTERFACE/CONTROL REGISTER V ±0.2% maximum @ 25°C, 25 ppm/°C maximum DRIVE 69 dB SINAD at 50 kHz input frequency No pipeline delays
001
High speed parallel interface with word/byte modes DB0 DB11 CS RD WR W/B DGND
04751-
Full shutdown mode: 2 µA maximum
Figure 1.
32-lead LFCSP and TQFP packages GENERAL DESCRIPTION
The AD7938-6 is a 12-bit, high speed, low power, successive features flexible power management options. An on-chip approximation (SAR) analog-to-digital converter (ADC). The control register al ows the user to set up different operating part operates from a single 2.7 V to 5.25 V power supply and conditions, including analog input range and configuration, features throughput rates up to 625 kSPS. The part contains a output coding, power management, and channel sequencing. low noise, wide bandwidth, differential track-and-hold
PRODUCT HIGHLIGHTS
amplifier that can handle input frequencies up to 50 MHz. 1. High throughput with low power consumption. The AD7938-6 features eight analog input channels with a 2. Eight analog inputs with a channel sequencer. channel sequencer that al ows a preprogrammed selection of 3. Accurate on-chip 2.5 V reference. channels to be converted sequential y. The part can operate 4. Single-ended, pseudo differential, or ful y differential with either single-ended, ful y differential, or pseudo differential analog inputs that are software selectable. analog inputs. 5. Single-supply operation with VDRIVE function. The VDRIVE function al ows the paral el interface to connect directly to The conversion process and data acquisition are control ed 3 V or 5 V processor systems independent of V using standard control inputs that al ow easy interfacing with DD. 6. No pipeline delay. microprocessors and DSPs. The input signal is sampled on the 7. Accurate control of the sampling instant via a CONVST falling edge of CONVST and the conversion is initiated at input and once-off conversion control. this point. The AD7938-6 has an accurate on-chip 2.5 V reference that
Table 1.
can be used as the reference source for the analog-to-digital
Similar Device No. of Bits No. of Channels Speed
conversion. Alternatively, this pin can be overdriven to provide AD7938/AD7939 12/10 8 1.5 MSPS an external reference. AD7933/AD7934 10/12 4 1.5 MSPS AD7934-6 12 4 625 kSPS The AD7938-6 uses advanced design techniques to achieve very low power dissipation at high throughput rates. The part also
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Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY ON-CHIP REGISTERS CONTROL REGISTER SEQUENCER OPERATION Writing to the Control Register to Program the Sequencer SHADOW REGISTER CIRCUIT INFORMATION CONVERTER OPERATION ADC TRANSFER FUNCTION TYPICAL CONNECTION DIAGRAM ANALOG INPUT STRUCTURE ANALOG INPUTS Single-Ended Mode Differential Mode Driving Differential Inputs Using an Op Amp Pair Pseudo Differential Mode ANALOG INPUT SELECTION Traditional Multichannel Operation (SEQ = 0, SHDW = 0) Using the Sequencer: Programmable Sequence (SEQ = 0, SHDW = 1 ) Consecutive Sequence (SEQ = 1, SHDW = 1) REFERENCE Digital Inputs VDRIVE Input PARALLEL INTERFACE Reading Data from the AD7938-6 Writing Data to the AD7938-6 POWER MODES OF OPERATION Normal Mode (PM1 = PM0 = 0) Autoshutdown (PM1 = 0; PM0 = 1) Autostandby (PM1 = 1; PM0 = 0) Full Shutdown Mode (PM1 =1; PM0 = 1) POWER vs. THROUGHPUT RATE MICROPROCESSOR INTERFACING AD7938-6 to ADSP-21xx Interface AD7938-6 to ADSP-21065L Interface AD7938-6 to TMS32020, TMS320C25, and TMS320C5x Interface AD7938-6 to 80C186 Interface APPLICATION HINTS GROUNDING AND LAYOUT PCB DESIGN GUIDELINES FOR CHIP SCALE PACKAGE EVALUATING THE AD7938-6 PERFORMANCE OUTLINE DIMENSIONS ORDERING GUIDE