AD7818ARM(2000) Просмотр технического описания (PDF) - Analog Devices

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AD7818ARM
(Rev.:2000)

Single- and 4-Channel, 9 μ
s, 10-Bit ADCs with On-Chip Temperature Sensor

Analog Devices 

Pin Mnemonic

1

CONVST

2

BUSY

3

OTI

4

CS

5

AGND

6

REFIN

7–10 VIN1 to VIN4

11

VDD

12

DGND

13

DOUT

14

DIN

15

SCLK

16

RD/WR

AD7816/AD7817/AD7818

AD7817 PIN FUNCTION DESCRIPTIONS

Description

Logic Input Signal. The convert start signal. A 10-bit analog-to-digital conversion is initiated on the

falling edge of this signal. The falling edge of this signal places the track/hold in hold mode. The track/

hold goes into track mode again at the end of the conversion. The state of the CONVST signal is checked

at the end of a conversion. If it is logic low, the AD7817 will power-down—see Operating Mode section

of the data sheet.

Logic Output. The busy signal is logic high during a temperature or voltage A/D conversion. The signal

can be used to interrupt a microcontroller when a conversion has finished.

Logic Output. The Over-Temperature Indicator (OTI) is set logic low if the result of a conversion on

Channel 0 (Temperature Sensor) is greater that an eight bit word in the Over-Temperature Register

(OTR). The signal is reset at the end of a serial read operation, i.e., a rising RD/WR edge when CS is low.

Logic Input Signal. The chip select signal is used to enable the serial port of the AD7817. This is neces-

sary if the AD7817 is sharing the serial bus with more than one device.

Analog Ground. Ground reference for track/hold, comparator and capacitor DAC.

Analog Input. An external 2.5 V reference can be connected to the AD7817 at this pin. To enable the on-

chip reference the REFIN pin should be tied to AGND. If an external reference is connected to the

AD7817, the internal reference will shut down.

Analog Input Channels. The AD7817 has four analog input channels. The input channels are single-

ended with respect to AGND (analog ground). The input channels can convert voltage signals in the

range 0 V to VREF. A channel is selected by writing to the Address Register of the AD7817—see Control

Byte section.

Positive Supply Voltage, +2.7 V to +5.5 V.

Digital Ground. Ground reference for digital circuitry.

Logic Output With a High Impedance State. Data is clocked out of the AD7817 serial port at this pin.

This output goes into a high impedance state on the falling edge of RD/WR or on the rising edge of the

CS signal, whichever occurs first.

Logic Input. Data is clocked into the AD7817 at this pin.

Clock Input For the Serial Port. The serial clock is used to clock data into and out of the AD7817. Data

is clocked out on the falling edge and clocked in on the rising edge.

Logic Input Signal. The read/write signal is used to indicate to the AD7817 whether the data transfer

operation is a read or a write. The RD/WR should be set logic high for a read operation and logic low for

a write operation.

PIN CONFIGURATION

SOIC/TSSOP

CONVST 1

16 RD/WR

BUSY 2

15 SCLK

OTI 3

14 DIN

CS 4 AD7817 13 DOUT

TOP VIEW

AGND 5 (Not to Scale) 12 DGND

REFIN 6

11 VDD

VIN1 7

10 VIN4

VIN2 8

9 VIN3

REV. A

–7–

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