EVAL-AD7818EB 查看數據表（PDF） - Analog Devices

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EVAL-AD7818EB

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

Analog Devices 

AD7816/AD7817/AD7818

0.8

0.7

0.6

AIR

0.5

0.4

FLUID

0.3

0.2

HEAT SINK

0.1

0.0

–0.01

0

2

4

6

8

10 12 14 16

TIME – secs

Figure 14. Self-Heating Effect in Air, Fluid, and in Thermal

Contact with a Heat Sink

0.25

0.20

0.15

0.10

FLUID

AIR

HEATSINK

OPERATING MODES

The AD7816, AD7817, and AD7818 have two possible modes

of operation depending on the state of the CONVST pulse at

the end of a conversion.

Mode 1

In this mode of operation the CONVST pulse is brought high

before the end of a conversion, i.e., before the BUSY goes low

(see Figure 16). When operating in this mode a new conversion

should not be initiated until 100 ns after the end of a serial read

operation. This quiet time is to allow the track/hold to accu-

rately acquire the input signal after a serial read.

Mode 2

When the AD7816, AD7817, and AD7818 are operated in Mode

2 (see Figure 17), they automatically power down at the end of

a conversion. The CONVST is brought low to initiate a conver-

sion and is left logic low until after the end of the conversion. At

this point, i.e., when BUSY goes low, the devices will power-

down. The devices are powered up again on the rising edge of

the CONVST signal. Superior power performance can be

achieved in this mode of operation by powering up the AD7816,

AD7817, and AD7818 only to carry out a conversion (see Power

vs. Throughput section). In Figure 17 the CS line is applicable

to the AD7817 only.

0.05

0.00

–0.05

0.0

0.5

1.0

1.5

2.0

TIME – secs

Figure 15. Self-Heating Effect in Air, Fluid, and in Thermal

Contact with a Heat Sink

CONVST

BUSY

CS

OTI

t1

t2

t3

t17

t15

t16

RD/ WR

SCLK

DIN

DOUT

DB7 – DB0

Figure 16. Mode 1 Operation

DB7(DB9) – DB0

–14–

REV. C

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