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参数资料
| 型号： | MAX1246 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | +2.7V, Low-Power, 4-Channel, Serial 12-Bit ADCs in QSOP-16 |
| 中文描述： | +2.7V、低功耗、4通道、串行12位ADC，QSOP-16封装 |
| 文件页数： | 19/24页 |
| 文件大小： | 223K |
| 代理商： | MAX1246 |
At VREF, the DC input resistance is a minimum of 18k
.
During conversion, an external reference at VREF must
deliver up to 350μA DC load current and have 10
or
less output impedance. If the reference has a higher
output impedance or is noisy, bypass it close to the
VREF pin with a 4.7μF capacitor.
Using the REFADJ input makes buffering the external
reference unnecessary. To use the direct VREF input,
disable the internal buffer by tying REFADJ to V
DD
. In
power-down, the input bias current to REFADJ can be
as much as 25μA with REFADJ tied to V
DD
. Pull
REFADJ to AGND to minimize the input bias current in
power-down.
T ransfer Func tion
Table 7 shows the full-scale voltage ranges for unipolar
and bipolar modes.
The external reference must have a temperature coeffi-
cient of 4ppm/°C or less to achieve accuracy to within
1LSB over the 0°C to +70°C commercial temperature
range.
Figure 16 depicts the nominal, unipolar input/output
(I/O) transfer function, and Figure 17 shows the bipolar
input/output transfer function. Code transitions occur
halfway between successive-integer LSB values.
Output coding is binary, with 1LSB = 610μV (2.500V /
4096) for unipolar operation, and 1LSB = 610μV
[(2.500V / 2 - -2.500V / 2) / 4096] for bipolar operation.
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
digital lines underneath the ADC package.
Figure 18 shows the recommended system ground
connections. Establish a single-point analog ground
(star ground point) at AGND, separate from the logic
ground. Connect all other analog grounds and DGND
to the star ground. No other digital system ground
should be connected to this ground. For lowest-noise
operation, the ground return to the star ground’s power
supply should be low impedance and as short as
possible.
High-frequency noise in the V
DD
power supply may
affect the high-speed comparator in the ADC. Bypass
the supply to the star ground with 0.1μF and 1μF
capacitors close to pin 1 of the MAX1246/MAX1247.
Minimize capacitor lead lengths for best supply-noise
rejection. If the power supply is very noisy, a 10
resis-
tor can be connected as a lowpass filter (Figure 18).
High-S peed Digital Interfac ing with QS PI
The MAX1246/MAX1247 can interface with QSPI using
the circuit in Figure 19 (f
SCLK
= 2.0MHz, CPOL = 0,
CPHA = 0). This QSPI circuit can be programmed to do a
conversion on each of the four channels. The result is
stored in memory without taxing the CPU, since QSPI
incorporates its own microsequencer.
The MAX1246/MAX1247 are QSPI compatible up to its
maximum external clock frequency of 2MHz.
M
+2.7V, Low-Power, 4-Channel,
S erial 12-Bit ADCs in QS OP-16
______________________________________________________________________________________
19
OUTPUT CODE
FULL-SCALE
TRANSITION
11
. . .
111
11
. . .
110
11
. . .
101
00
. . .
011
00
. . .
010
00
. . .
001
00
. . .
000
1
2
3
0
(COM)
FS
FS - 3/2LSB
FS = VREF + COM
ZS = COM
1LSB = 4096
INPUT VOLTAGE (LSB)
Figure 16. Unipolar Transfer Function, Full Scale (FS) = VREF
+ COM, Zero Scale (ZS) = COM
UNIPOLAR MODE
BIPOLAR MODE
Full Scale
Zero Scale
Positive
Full Scale
Zero
Scale
Negative
Full Scale
VREF + COM
COM
VREF / 2
+ COM
COM
-VREF / 2
+ COM
Table 7. Full Scale and Zero Scale
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| MAX1246ACEE+ | 功能描述:模数转换器 - ADC 12-Bit 4Ch 133ksps 3.6V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX1246ACEE+T | 功能描述:模数转换器 - ADC 12-Bit 4Ch 133ksps 3.6V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX1246ACEE-T | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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