AD7791 데이터 시트보기 (PDF) - Analog Devices

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AD7791

Low Power, Buffered 24-Bit Sigma-Delta ADC

Analog Devices 

AD7791

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

SCLK 1

10 DIN

CS 2 AD7791 9 DOUT/RDY

AIN(+) 3 TOP VIEW 8 VDD

AIN(–) 4 (Not to Scale) 7 GND

REF(+) 5

6 REF(–)

04227-0-005

Figure 5. Pin Configuration

Table 4. Pin Function Descriptions

Pin

No. Mnemonic Function

1 SCLK

Serial Clock Input for Data Transfers to and

from the ADC. The SCLK has a Schmitt-

triggered input, making the interface

suitable for opto-isolated applications. The

serial clock can be continuous with all data

transmitted in a continuous train of pulses.

Alternatively, it can be a noncontinuous

clock with the information being trans-

mitted to or from the ADC in smaller

batches of data.

2 CS

Chip Select Input. This is an active low logic

input used to select the ADC. CS can be

used to select the ADC in systems with

more than one device on the serial bus or as

a frame synchronization signal in communi-

cating with the device. CS can be hardwired

low, allowing the ADC to operate in 3-wire

mode with SCLK, DIN, and DOUT used to

interface with the device.

3 AIN(+)

Analog Input. AIN(+) is the positive terminal

of the fully differential analog input.

4 AIN(–)

Analog Input. AIN(–) is the negative termi-

nal of the fully differential analog input.

5 REFIN(+) Positive Reference Input. REFIN(+) can lie

anywhere between VDD and GND + 0.1 V.

The nominal reference voltage (REFIN(+) –

REFIN(–)) is 2.5 V, but the part functions

with a reference from 0.1 V to VDD.

Pin

No. Mnemonic Function

6 REFIN(–)

Negative Reference Input. This reference

input can lie anywhere between GND and

VDD – 0.1 V.

7 GND

Ground Reference Point.

8

VDD

Supply Voltage, 2.5 V to 5.25 V.

9 DOUT/RDY Serial Data Output/Data Ready Output.

DOUT/RDY serves a dual purpose . It functions

as a serial data output pin to access the out-

put shift register of the ADC. The output shift

register can contain data from any of the

on-chip data or control registers. In addition,

DOUT/RDY operates as a data ready pin,

going low to indicate the completion of a

conversion. If the data is not read after the

conversion, the pin will go high before the

next update occurs.

The DOUT/RDY falling edge can be used as an

interrupt to a processor, indicating that valid

data is available. With an external serial clock,

the data can be read using the DOUT/RDY pin.

With CS low, the data/control word informa-

tion is placed on the DOUT/RDY pin on the

SCLK falling edge and is valid on the SCLK

rising edge.

The end of a conversion is also indicated by

the RDY bit in the status register. When CS is

high, the DOUT/RDY pin is three-stated but

the RDY bit remains active.

10 DIN

Serial Data Input to the Input Shift Register

on the ADC. Data in this shift register is

transferred to the control registers within

the ADC, the register selection bits of the

communications register identifying the

appropriate register.

Rev. 0 | Page 8 of 20

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