AD7264 Просмотр технического описания (PDF) - Analog Devices

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AD7264

1 MSPS, 14-Bit, Simultaneous Sampling SAR ADC with PGA and Four Comparators

Analog Devices 

Pin No.

48, 47, 46, 45

13, 14, 15, 16

5, 6, 8, 19, 42

28

30, 29, 26, 25

32, 31

40, 39, 38, 37

27

44, 17

24

AD7264

Mnemonic

CA+, CA−,

CB+, CB−

CC+, CC−,

CD+, CD−

AGND

DGND

COUTA, COUTB,

COUTC, COUTD

DOUTA, DOUTB

G0, G1, G2, G3

VDRIVE

CA_CB_GND,

CC_CD_GND

REFSEL

Description

Comparator Inputs. These pins are the inverting and noninverting analog inputs for Comparator A

and Comparator B. These two comparators have very low power consumption.

Comparator Inputs. These pins are the inverting and noninverting analog inputs for Comparator C

and Comparator D. These two comparators offer very fast propagation delays.

Analog Ground. Ground reference point for all analog circuitry on the AD7264. All analog input

signals and any external reference signal should be referred to this AGND voltage. All AGND pins

should be connected to the AGND plane of a system. The AGND, DGND, CA_CB_GND, and

CC_CD_GND voltages should ideally be at the same potential and must not be more than 0.3 V apart,

even on a transient basis. CA_CB_GND and CC_CD_GND can be tied to AGND.

Digital Ground. Ground reference point for all digital circuitry on the AD7264. The DGND pin should

be connected to the DGND plane of a system. The DGND and AGND voltages should ideally be at

the same potential and must not be more than 0.3 V apart, even on a transient basis.

Comparator Outputs. These pins provide a CMOS (push-pull) output from each respective

comparator. These are digital output pins with logic levels determined by the VDRIVE supply.

Serial Data Outputs. The data output from the AD7264 is supplied to each pin as a serial data stream

in twos complement format. The bits are clocked out on the falling edge of the SCLK input. A total of

33 SCLK cycles are required to perform the conversion and access the 14-bit data. During the

conversion process, the data output pins are in three-state and, when the conversion is completed,

the 19th SCLK edge clocks out the MSB. The data appears simultaneously on both pins from the

simultaneous conversions of both ADCs. The data is provided MSB first. If CS is held low for a further

14 SCLK cycles on either DOUTA or DOUTB following the initial 33 SCLK cycles, the data from the other

ADC follows on the DOUT pin. This allows data from a simultaneous conversion on both ADCs to be

gathered in serial format on either DOUTA or DOUTB using only one serial port.

Logic Inputs. These pins are used to program the gain setting of the front-end amplifiers. If all four

pins are tied low, the PD0/DIN pin acts as a data input pin, DIN, and all programming is made via the

control register. See Table 6.

Logic Power Supply Input, 2.7 V to 5.25 V. The voltage supplied at this pin determines at what

voltage the interface operates, including the comparator outputs. This pin should be decoupled

to DGND.

Comparator Ground. Ground reference point for all comparator circuitry on the AD7264. Both the

CA_CB_GND and CC_CD_GND pins should connect to the GND plane of a system and can be tied to

AGND. The DGND, AGND, CA_CB_GND, and CC_CD_GND voltages should ideally be at the same

potential and must not be more than 0.3 V apart, even on a transient basis.

Internal/External Reference Selection. Logic input. If this pin is tied to a logic high voltage, the

on-chip 2.5 V reference is used as the reference source for both ADC A and ADC B. If the REFSEL

pin is tied to GND, an external reference can be supplied to the AD7264 through the VREFA and/or

VREFB pins.

Rev. A | Page 9 of 32

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