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參數(shù)資料
型號(hào)： MAX1238KEEE+
廠商： Maxim Integrated Products
文件頁(yè)數(shù)： 10/22頁(yè)
文件大?。?/td> 0K
描述： IC ADC 12BIT SERIAL 16-QSOP
標(biāo)準(zhǔn)包裝： 100
位數(shù)： 12
采樣率（每秒）： 94.4k
數(shù)據(jù)接口： I²C，串行
轉(zhuǎn)換器數(shù)目： 1
功率耗散（最大）： 666.7mW
電壓電源： 單電源
工作溫度： -40°C ~ 85°C
安裝類(lèi)型： 表面貼裝
封裝/外殼： 16-SSOP（0.154"，3.90mm 寬）
供應(yīng)商設(shè)備封裝： 16-QSOP
包裝： 管件
輸入數(shù)目和類(lèi)型： 12 個(gè)單端，單極；12 個(gè)單端，雙極；6 個(gè)差分，單極；6 個(gè)差分，雙極
MAX1236–MAX1239
Wake-up is invisible when using an external reference
or VDD as the reference.
Automatic shutdown results in dramatic power savings,
particularly at slow conversion rates and with internal
clock. For example, at a conversion rate of 10ksps, the
average supply current for the MAX1237 is 60A (typ) and
drops to 6A (typ) at 1ksps. At 0.1ksps the average sup-
ply current is just 1A, or a minuscule 3W of power con-
sumption, see Average Supply Current vs. Conversion
Rate in the
Typical Operating Characteristics section.
Reference Voltage
SEL[2:0] of the setup byte (Table 1) control the reference
and the AIN_/REF configuration (Table 6). When
AIN_/REF is configured to be a reference input or refer-
ence output (SEL1 = 1), differential conversions on
AIN_/REF appear as if AIN_/REF is connected to GND
(see Note 2 and Table 4). Single-ended conversion in
scan mode AIN_/REF is ignored by the internal limiter,
which sets the highest available channel at AIN2 or
AIN10.
Internal Reference
The internal reference is 4.096V for the MAX1236/
MAX1238 and 2.048V for the MAX1237/MAX1239. SEL1 of
the setup byte controls whether AIN_/REF is used for an
analog input or a reference (Table 6). When AIN_/REF is
configured to be an internal reference output (SEL[2:1] =
11), decouple AIN_/REF to GND with a 0.1F capacitor
and a 2kΩ series resistor (see the Typical Operating
Circuit ). Once powered up, the reference always remains
on until reconfigured. The internal reference requires 10ms
to wake up and is accessed using SEL0 (Table 6). When
in shutdown, the internal reference output is in a high-
impedance state. The reference should not be used to
supply current for external circuitry. The internal reference
does not require an external bypass capacitor and works
best when not connected to the pin (SEL1 = 0).
External Reference
The external reference can range from 1V to VDD. For
maximum conversion accuracy, the reference must be
able to deliver up to 40A and have an output imped-
ance of 500Ω or less. If the reference has a higher out-
put impedance or is noisy, bypass it to GND as close to
AIN_/REF as possible with a 0.1F capacitor.
Transfer Functions
Output data coding for the MAX1236–MAX1239 is bina-
ry in unipolar mode and two’s complement in bipolar
mode with 1 LSB = (VREF/2N) where “N” is the number of
bits (12). Code transitions occur halfway between suc-
cessive-integer LSB values. Figures 12 and 13 show
the input/output (I/O) transfer functions for unipolar and
bipolar operations, respectively.
Layout, Grounding, and Bypassing
Only use PC boards. Wire-wrap configurations are not
recommended since the layout should ensure proper
separation of analog and digital traces. Do not run ana-
log and digital lines parallel to each other, and do not
layout digital signal paths underneath the ADC pack-
2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
18
______________________________________________________________________________________
SEL2
SEL1
SEL0
REFERENCE VOLTAGE
AIN_/REF
INTERNAL REFERENCE
STATE
00
X
VDD
Analog Input
Always Off
0
1
X
External Reference
Reference Input
Always Off
1
0
Internal Reference
Analog Input
Always Off
1
0
1
Internal Reference
Analog Input
Always On
1
0
Internal Reference
Reference Output
Always Off
1
Internal Reference
Reference Output
Always On
Table 6. Reference Voltage and AIN_/REF Format
OUTPUT CODE
FULL-SCALE
TRANSITION
11 . . . 111
11 . . . 110
11 . . . 101
00 . . . 011
00 . . . 010
00 . . . 001
00 . . . 000
12
3
0
FS
FS - 3/2 LSB
FS = VREF
ZS = GND
INPUT VOLTAGE (LSB)
MAX1236–
MAX1239
1 LSB =
VREF
4096
Figure 12. Unipolar Transfer Function
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參數(shù)描述
MAX1238KEEE+ 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Integrated Circuits (ICs) 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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
MAX1238KEEE+T 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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
MAX1238KEEE-T 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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
MAX1238LEEE 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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
MAX1238LEEE+ 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(lèi)型:Differential 信噪比:107 dB 接口類(lèi)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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