參數(shù)資料
型號(hào): MAX189
廠商: Maxim Integrated Products, Inc.
元件分類: ADC
英文描述: +5V, Low-Power, 12-Bit Serial ADCs(8.5μs轉(zhuǎn)換時(shí)間,單通道,串行12位A/D轉(zhuǎn)換器)
中文描述: +5V、低功耗、12位串行ADC
文件頁數(shù): 13/20頁
文件大小: 177K
代理商: MAX189
Minimum cycle time is accomplished by using DOUT’s
rising edge as the EOC signal. Clock out the data with
13 clock cycles at full speed. Raise
CS
after the conver-
sion’s LSB has been read. After the specified minimum
time, t
,
CS
can be pulled low again to initiate the
next conversion.
Output Coding and T ransfer Func tion
The data output from the MAX187/MAX189 is binary,
and Figure 10 depicts the nominal transfer function.
Code transitions occur halfway between successive
integer LSB values. If V
REF
= +4.096V, then
1 LSB = 1.00mV or 4.096V/4096.
_____________Dynamic Performanc e
High-speed sampling capability and a 75ksps through-
put make the MAX187/MAX189 ideal for wideband sig-
nal processing. To support these and other related
applications, Fast Fourier Transform (FFT) test tech-
niques are used to guarantee the ADC’s dynamic fre-
quency response, distortion, and noise at the rated
throughput. Specifically, this involves applying a low-
distortion sine wave to the ADC input and recording the
digital conversion results for a specified time. The data
is then analyzed using an FFT algorithm that deter-
mines its spectral content. Conversion errors are then
seen as spectral elements outside of the fundamental
input frequency. ADCs have traditionally been evaluat-
ed by specifications such as Zero and Full-Scale Error,
Integral Nonlinearity (INL), and Differential Nonlinearity
(DNL). Such parameters are widely accepted for speci-
fying performance with DC and slowly varying signals,
but are less useful in signal-processing applications,
where the ADC’s impact on the system transfer function
is the main concern. The significance of various DC
errors does not translate well to the dynamic case, so
different tests are required.
S ignal-to-Noise Ratio and
Effec tive Number of Bits
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS amplitude of all other ADC output signals. The
input bandwidth is limited to frequencies above DC and
below one-half the ADC sample (conversion) rate.
The theoretical minimum ADC noise is caused by quan-
tization error and is a direct result of the ADC’s resolu-
tion: SINAD = (6.02N + 1.76)dB, where N is the number
of bits of resolution. An ideal 12-bit ADC can, therefore,
do no better than 74dB. An FFT plot of the output
shows the output level in various spectral bands. Figure
11 shows the result of sampling a pure 10kHz sine
wave at a 75ksps rate with the MAX187/MAX189.
M
+5V, Low-Power, 12-Bit S erial ADCs
______________________________________________________________________________________
13
11
111
11
110
11
101
00
011
00
010
00
001
00
000
0
1
2
FS
OUTPUT CODE
FS - 3/2LSB
INPUT VOLTAGE (LSBs)
FS = +4.096V
1LSB = FS
FULL-SCALE
TRANSITION
3
A
20
0
-20
-40
-60
-80
-100
-120
-140
0
18.75
37.5
f
S
= 75ksps
f
T
= 10kHz
T
A
= +25°C
FREQUENCY (kHz)
Figure 11. MAX187/MAX189 FFT plot
Figure 10. MAX187/MAX189 Unipolar Transfer Function,
4.096V = Full Scale
相關(guān)PDF資料
PDF描述
MAX187ACWE Fixed-Point Digital Signal Processor 288-BGA MICROSTAR
MAX187AMJA Fixed-Point Digital Signal Processor 288-BGA MICROSTAR
MAX187CEPA +5V, Low-Power, 12-Bit Serial ADCs
MAX189CEPA 031-0560-161
MAX189BEWE CANMS3121E16-26SF0
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