AD7866| Datasheet

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Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface AD7866
FEATURES Dual 12-Bit, 2-Channel ADC Fast Throughput Rate: 1 MSPS Specified for VDD of 2.7 V to 5.25 V Low Power 11.4 mW Max at 1 MSPS with 3 V Supplies 24 mW Max at 1 MSPS with 5 V Supplies Wide Input Bandwidth 70 dB SNR at 300 kHz Input Frequency On-Board Reference 2.5 V 40 C to +125 C Operation Flexible Power/Throughput Rate Management Simultaneous Conversion/Read No Pipeline Delays High Speed Serial Interface SPITM/QSPITM/ MICROWIRETM/DSP Compatible Shutdown Mode: 1 A Max 20-Lead TSSOP Package GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM
VREF DCAPA REF SELECT AVDD DVDD 2.5V REF VA1 VA2

BUF 12-BIT SUCCESSIVE APPROXIMATION ADC

AD7866
OUTPUT DRIVERS DOUTA

MUX

T/H

CONTROL LOGIC

A0 RANGE SCLK CS VDRIVE

VB1 VB2

MUX

T/H

12-BIT SUCCESSIVE APPROXIMATION ADC

OUTPUT DRIVERS

DOUT B

BUF

AGND

DCAPB

DGND

The AD7866 is a dual 12-bit high speed, low power, successive approximation ADC. The part operates from a single 2.7 V to 5.25 V power supply and features throughput rates up to 1 MSPS. The device contains two ADCs, each preceded by a low noise, wide bandwidth track-and-hold amplifier that can handle input frequencies in excess of 10 MHz. The conversion process and data acquisition are controlled using standard control inputs, allowing easy interfacing to microprocessors or DSPs. The input signal is sampled on the falling edge of CS; conversion is also initiated at this point. The conversion time is determined by the SCLK frequency. There are no pipelined delays associated with the part. The AD7866 uses advanced design techniques to achieve very low power dissipation at high throughput rates. With 3 V supplies and 1 MSPS throughput rate, the part consumes a maximum of 3.8 mA. With 5 V supplies and 1 MSPS, the current consumption is a maximum of 4.8 mA. The part also offers flexible power/throughput rate mana
gement when operating in sleep mode. The analog input range for the part can be selected to be a 0 V to VREF range or a 2 VREF range with either straight binary or twos complement output coding. The AD7866 has an on-chip 2.5 V reference that can be overdriven if an external reference is preferred. Each on-board ADC can also be supplied with a separate individual external reference. The AD7866 is available in a 20-lead thin shrink small outline (TSSOP) package. REV. A
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PRODUCT HIGHLIGHTS

1. The AD7866 features two complete ADC functions, allowing simultaneous sampling and conversion of two channels. Each ADC has a 2-channel input multiplexer. The conversion result of both channels is available simultaneously on separate data lines, or may be taken on one data line if only one serial port is available. 2. High Throughput with Low Power Consumption--The AD7866 offers a 1 MSPS throughput rate with 11.4 mW maximum power consumption when operating at 3 V. 3. Flexible Power/Throughput Rate Management--The conversion rate is determined by the serial clock, allowing the power consumption to be reduced as the conversion time is reduced through a SCLK frequency increase. Power efficiency can be maximized at lower throughput rates if the part enters sleep during conversions. 4. No Pipeline Delay--The part features two standard successive approximation ADCs with accurate control of the sampling instant via a CS input and once off conversion control.