參數(shù)資料
型號(hào): MAX147AMJP
廠商: MAXIM INTEGRATED PRODUCTS INC
元件分類: ADC
英文描述: +2.7Low-Power, 8-Channel, Serial 12-Bit ADCs
中文描述: 8-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, SERIAL ACCESS, CDIP20
封裝: CERAMIC, DIP-20
文件頁(yè)數(shù): 10/24頁(yè)
文件大?。?/td> 198K
代理商: MAX147AMJP
M
+2.7V, Low-Power, 8-Channel,
S erial 12-Bit ADCs
10
______________________________________________________________________________________
The time required for the T/H to acquire an input signal
is a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is high,
the acquisition time lengthens, and more time must be
allowed between conversions. The acquisition time,
t
ACQ
, is the maximum time the device takes to acquire
the signal, and is also the minimum time needed for the
signal to be acquired. It is calculated by the following
equation:
t
ACQ
= 9 x (R
S
+ R
IN
) x 16pF
where R
IN
= 9k
, R
S
= the source impedance of the
input signal, and t
ACQ
is never less than 1.5μs. Note
that source impedances below 1k
do not significantly
affect the ADC’s AC performance.
Higher source impedances can be used if a 0.01μF
capacitor is connected to the individual analog inputs.
Note that the input capacitor forms an RC filter with the
input source impedance, limiting the ADC’s signal
bandwidth.
Input Bandwidth
The ADC’s input tracking circuitry has a 2.25MHz
small-signal bandwidth, so it is possible to digitize
high-speed transient events and measure periodic sig-
nals with bandwidths exceeding the ADC’s sampling
rate by using undersampling techniques. To avoid
high-frequency signals being aliased into the frequency
band of interest, anti-alias filtering is recommended.
Analog Input Protec tion
Internal protection diodes, which clamp the analog input
to V
DD
and AGND, allow the channel input pins to swing
from AGND - 0.3V to V
DD
+ 0.3V without damage.
However, for accurate conversions near full scale, the
inputs must not exceed V
DD
by more than 50mV or be
lower than AGND by 50mV.
If the analog input exceeds 50mV beyond the sup-
plies, do not forward bias the protection diodes of
off channels over 2mA.
Quic k Look
To quickly evaluate the MAX146/MAX147’s analog per-
formance, use the circuit of Figure 5. The MAX146/
MAX147 require a control byte to be written to DIN
before each conversion. Tying DIN to +3V feeds in con-
trol bytes of $FF (HEX), which trigger single-ended
unipolar conversions on CH7 in external clock mode
without powering down between conversions. In exter-
nal clock mode, the SSTRB output pulses high for one
clock period before the most significant bit of the 12-bit
conversion result is shifted out of DOUT. Varying the
analog input to CH7 will alter the sequence of bits from
DOUT. A total of 15 clock cycles is required per con-
version. All transitions of the SSTRB and DOUT outputs
occur on the falling edge of SCLK.
0.1
μ
F
2.5V
+3V
V
DD
DGND
AGND
COM
CS
SCLK
DIN
DOUT
SSTRB
SHDN
+3V
N.C.
0.01
μ
F
CH7
REFADJ
VREF
C1
0.1
μ
F
0V TO
2.500V
ANALOG
INPUT
OSCILLOSCOPE
CH1
CH2
CH3
CH4
* FULL-SCALE ANALOG INPUT, CONVERSION RESULT = $FFF (HEX)
MAX146
MAX147
+3V
2MHz
OSCILLATOR
SCLK
SSTRB
DOUT*
COMP
1000pF
V
OUT
+3V
MAX872
OPTIONAL FOR MAX146,
REQUIRED FOR MAX147
Figure 5. Quick-Look Circuit
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MAX147BCAP+ 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
MAX147BCAP+T 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32
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