AD7818ARZ-REEL7 Просмотр технического описания (PDF) - Analog Devices
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AD7818ARZ-REEL7 Datasheet PDF : 20 Pages
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Data Sheet
Figure 16 represents the worst-case effects of self-heating. The
heater delivered 6 mW to the interior of the package in all cases.
This power level is equivalent to the ADC continuously converting
at 100 kSPS. The effects of the self-heating can be reduced at
lower ADC throughput rates by operating in Mode 2 (see
Operating Modes section). When operating in this mode, the
on-chip power dissipation reduces dramatically and, as a
consequence, the self-heating effects.
0.8
0.7
0.6
AIR
0.5
0.4
FLUID
0.3
0.2
HEAT SINK
0.1
0
–0.1
0
2
4
6
8
10
12
14
16
TIME (Seconds)
Figure 16. Self-Heating Effect in Air, Fluid, and Thermal Contact with a Heat Sink
AD7817/AD7818
OPERATING MODES
The AD7817/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, that is, before BUSY goes low
(see Figure 17). When operating in this mode, do not initiate a
new conversion until 100 ns after the end of a serial read operation.
This quiet time is to allow the track-and-hold to accurately acquire
the input signal after a serial read.
Mode 2
In this mode of operation, AD7817/AD7818 automatically power
down at the end of a conversion (see Figure 18). The CONVST is
brought low to initiate a conversion and is left logic low until after
the end of the conversion. At this point, that is, when BUSY goes
low, the devices 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 AD7817/AD7818 only
to carry out a conversion (see the Power vs. Throughput section).
In Figure 18, the CS line is applicable to the AD7817 only.
Rev. D | Page 15 of 20
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