參數(shù)資料
型號: AD7946BCPZRL7
廠商: Analog Devices Inc
文件頁數(shù): 7/24頁
文件大?。?/td> 0K
描述: IC ADC 14BIT 500KSPS 10-LFCSP
標準包裝: 1
系列: PulSAR®
位數(shù): 14
采樣率(每秒): 500k
數(shù)據(jù)接口: DSP,MICROWIRE?,QSPI?,串行,SPI?
轉(zhuǎn)換器數(shù)目: 1
功率耗散(最大): 19mW
電壓電源: 單電源
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 10-WFDFN 裸露焊盤,CSP
供應(yīng)商設(shè)備封裝: 10-LFCSP-WD(3x3)
包裝: 標準包裝
輸入數(shù)目和類型: 1 個偽差分,單極
其它名稱: AD7946BCPZRL7DKR
AD7946
Rev. A | Page 15 of 24
POWER SUPPLY
The AD7946 is specified at 4.5 V to 5.5 V. It uses two power
supply pins: a core supply VDD and a digital input/output
interface supply VIO. VIO allows direct interface with any
logic between 1.8 V and VDD. To reduce the supplies needed,
the VIO and VDD can be tied together. The AD7946 is
independent of power supply sequencing between VIO and
VDD. Additionally, it is very insensitive to power supply
variations over a wide frequency range, as shown in Figure 29,
which represents PSRR over frequency.
FREQUENCY (kHz)
P
S
RR
(dB)
04656-029
50
40
30
60
90
80
70
10
1
100
1k
10k
VDD = 5V
Figure 29. PSRR vs. Frequency
The AD7946 powers down automatically at the end of each
conversion phase and, therefore, the power scales linearly with
the sampling rate, as shown in Figure 30. This makes the part
ideal for low sampling rate (even a few Hz) and low battery-
powered applications.
04
65
6
-05
1
0.001
0.1
1
0.01
10
100
1000
10
100
1k
10k
100k
1M
SAMPLING RATE (SPS)
OP
E
R
A
T
ING
CUR
RE
NT
(
A
)
VIO
VDD = 5V
Figure 30. Operating Currents vs. Sampling Rate
SUPPLYING THE ADC FROM THE REFERENCE
For simplified applications, the AD7946, with its low operating
current, can be supplied directly using the reference circuit
shown in Figure 31. The reference line can be driven by one of
the following:
The system power supply directly.
A reference voltage with enough current output capability,
such as the ADR43x.
A reference buffer, such as the AD8031 or AD8603,
which can also filter the system power supply, as shown
AD8603
AD7946
VIO
REF
(NOTE 1)
VDD
10F
1F
10k
1k
47k
5V
1F
04
65
6
-03
1
NOTES
1. OPTIONAL REFERENCE BUFFER AND FILTER
Figure 31. Example of Application Circuit
SINGLE-SUPPLY APPLICATION
Figure 32 shows a typical 14-bit single-supply application. There
are different challenges to doing a single-supply, high resolution
design, and the ADA4841 addresses these nicely. The combina-
tion of low noise, low power, wide input range, rail-to-rail output,
and high speed make the ADA4841 a perfect driver solution for
low power, single-supply 14-bit ADCs, such as the AD7946. In a
single-supply system, one of the main challenges is to use the
amplifier in buffer mode to have the lowest output noise and
still preserve linearity compatible with the ADC. Rail-to-rail
input amplifiers usually have higher noise than the ADA4841
and cannot be used on their entire input range in buffer mode
because of the nonlinear region around the crossover point of
their input stage. The ADA4841, which has no crossover region
but has a wide linear input range from ground to 1 V below
positive rail, solves this issue, as shown in Figure 32, where it
can accept the 0 V to 4.096 V input range with a supply as low
as 5.2 V. This supply allows using a small, low dropout, low
temperature drift ADR364 reference voltage. Note that, like any
rail-to-rail output amplifier at the low end of its output range
close to ground, the ADA4841 can exhibit some nonlinearity on
a small region of approximately 25 mV from ground. The
ADA4841 drives a 1-pole, low-pass filter. This filter limits the
already very low noise contribution from the amplifier to the
AD7946.
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