參數(shù)資料
型號(hào)： MAX1108-MAX1109
廠商： Maxim Integrated Products, Inc.
英文描述： Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
中文描述： 單電源，低功耗，2通道，串行8位ADC
文件頁(yè)數(shù)： 18/20頁(yè)
文件大?。?/td> 185K
代理商： MAX1108-MAX1109
M
External Reference
To use an external reference, set bit 2 (I/EREF) and bit
1 (
REFSHDN
) of control byte to 0 and connect the
external reference (V
REF
between 1V and V
DD
) directly
at the REF pin. The DC input impedance at REF is
extremely high, consisting of leakage current only (typi-
cally 10nA). During a conversion, the reference must
be able to deliver up to 20μA average load current and
have an output impedance of 1k
or less at the conver-
sion clock frequency. If the reference has higher output
impedance or is noisy, bypass it close to the REF pin
with a 0.1μF capacitor. MAX1109 has an internal refer-
ence of +4.096V. To use the device with supply volt-
ages below 4.5V, external reference mode is required.
With an external reference voltage of less than +2.048V
(MAX1108) or +4.096V (MAX1109) at REF, the increase
in the ratio of the RMS noise to the LSB value (FS / 256)
results in performance degradation and decreased
dynamic range.
Internal Reference
To use the internal reference, set bit 2 (I/EREF) and bit 1
(
REFSHDN
) of the control byte to 1 and bypass REF with
a 1μF capacitor to ground. The internal reference can be
powered down after a conversion by setting bit 1 (
REF-
SHDN
) of the control byte to 0. When using the internal
reference, use MAX1108 and MAX1109 with supply volt-
age below 4.5V and above 4.5V, respectively.
T ransfer Func tion
Table 4 shows the full-scale voltage ranges for unipolar
and bipolar modes. Figure 12a depicts the nominal,
unipolar I/O transfer function, and Figure 12b shows the
bipolar I/O transfer function. The zero scale is deter-
mined by the input selection setting and is either COM,
GND, or CH1.
Code transitions occur at integer LSB values. Output
coding is straight binary for unipolar operation and
two’s complement for bipolar operation. With a +2.048V
reference, 1LSB = 8mV (V
REF
/ 256).
Layout, Grounding, and Bypassing
For best performance, use printed circuit boards. Wire-
wrap boards are not recommended. Board layout
should ensure that digital and analog signal lines are
separated from each other. Do not run analog and digi-
tal (especially clock) lines parallel to one another or run
digital lines underneath the ADC package.
Figure 13 shows the recommended system-ground
connections. A single-point analog ground (star-ground
point) should be established at the A/D ground.
Connect all analog grounds to the star ground. No digi-
tal-system ground should be connected to this point.
The ground return to the power supply for the star
ground should be low impedance and as short as pos-
sible for noise-free operation.
High-frequency noise in the V
DD
power supply may
affect the comparator in the ADC. Bypass the supply to
the star ground with 0.1μF and 1μF capacitors close to
the V
DD
pin of the MAX1108/MAX1109. Minimize
capacitor lead lengths for best supply-noise rejection. If
the power supply is very noisy, a 10
resistor can be
connected to form a lowpass filter.
S ingle-S upply, Low-Power,
2-Channel, S erial 8-Bit ADCs
18
______________________________________________________________________________________
OUTPUT CODE
FULL-SCALE
TRANSITION
11111111
11111110
11111101
00000011
00000010
00000001
00000000
1
2
3
0
FS
FS - 1LSB
FS = V
REF
+ COM
1LSB = V
REF
256
INPUT VOLTAGE (LSB)
(COM)
Figure 12a. Unipolar Transfer Function
01111111
01111110
OUTPUT CODE
00000010
00000001
00000000
11111111
11111110
11111101
10000001
10000000
-FS
COM
INPUT VOLTAGE (LSB)
+FS 2
REF
+ COM
+FS = V
REF
COM = V
REF
+ COM
-FS = -V
REF
1LSB = V
Figure 12b. Bipolar Transfer Function
相關(guān)PDF資料
PDF描述
MAX1108CUB Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
MAX1108 Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
MAX1108EUB Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
MAX1109CUB Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
MAX1109EUB Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1109 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Evaluation Kit for the MAX4135/MAX4136/MAX4137/MAX4138[MAX4135EVKIT ]
MAX1109CUB 功能描述:模數(shù)轉(zhuǎn)換器 - 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
MAX1109CUB+ 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2Ch Single-Supply Low-P Serial 8-Bit 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
MAX1109CUB+G07 制造商:Maxim Integrated Products 功能描述:10 PINS UMAX PKG - Tape and Reel
MAX1109CUB+T 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 2Ch Single-Supply Low-P Serial 8-Bit 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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