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參數(shù)資料
| 型號： | ADC78H89EVAL |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 7-Channel, 500 KSPS, 12-Bit A/D Converter |
| 中文描述： | 7通道，500 kSPS的，12位A / D轉(zhuǎn)換器 |
| 文件頁數(shù)： | 14/16頁 |
| 文件大小： | 828K |
| 代理商： | ADC78H89EVAL |
Applications Information
(Continued)
3.0 ADC78H89 TRANSFER FUNCTION
The output format of the ADC89H89 is straight binary. Code
transitions occur midway between successive integer LSB
values. The LSB width for the ADC78H89 is AV
DD
/ 4096.
The ideal transfer characteristic is shown in
Figure 4
.
4.0 TYPICAL APPLICATION CIRCUIT
A typical application of the ADC78H89 is shown in
Figure 5
.
The split analog and digital supplies are both provided in this
example by the National LP2950 low-dropout voltage regu-
lator, available in a variety of fixed and adjustable output
voltages. The analog supply is bypassed with a capacitor
network located close to the ADC78H89. The digital supply
is separated from the analog supply by an isolation resistor
and conditioned with additional bypass capacitors. The
ADC78H89 uses the analog supply (AV
DD
) as its reference
voltage, so it is very important that AV
possible. Because of the ADC78H89’s low power require-
ments, it is also possible to use a precision reference as a
power supply to maximize performance. The four-wire inter-
face is also shown connected to a microprocessor or DSP.
5.0 ANALOG INPUTS
An equivalent circuit for one of the ADC78H89’s input chan-
nels is shown in
Figure 6
. At the start of each conversion,
one of the ADC78H89’s seven channels are selected. Di-
odes D1 and D2 provide ESD protection for the analog
inputs. At no time should an analog input be beyond (AV
DD
+
300 mV) or (GND - 300 mV), as these ESD diodes will begin
conducting, which could cause erratic operation.
The capacitor C1 in
Figure 6
typically has a value of 3 pF,
and is mainly the package pin capacitance. Resistor R1 is
the on resistance of the multiplexer and track / hold switch,
and is typically 500 ohms. Capacitor C2 is the ADC78H89
sampling capacitor, and is typically 30 pF. The ADC78H89
will deliver best performance when driven by a low-
impedance source to eliminate distortion caused by the
charging of the sampling capacitor.
In applications where dynamic performance is critical, the
ADC78H89 might need to be driven with a low output-
impedance amplifier. In addition, when using the ADC78H89
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FIGURE 4. Ideal Transfer Characteristic
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FIGURE 5. Typical Application Circuit
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FIGURE 6. Equivalent Input Circuit
A
www.national.com
14
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ADC78H89 | 7 CHANNEL 500KSPS, 12 BIT A/D CONVERTER |
| ADC78H89CIMT | 7 CHANNEL 500KSPS, 12 BIT A/D CONVERTER |
| ADC78H89CIMTX | 7 CHANNEL 500KSPS, 12 BIT A/D CONVERTER |
| ADC78H90 | 8-Channel, 500 kSPS, 12-Bit A/D Converter |
| ADC78H90CIMT | 8-Channel, 500 kSPS, 12-Bit A/D Converter |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADC78H90 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:8-Channel, 500 kSPS, 12-Bit A/D Converter |
| ADC78H90CIMT | 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 |
| ADC78H90CIMT | 制造商:Texas Instruments 功能描述:12BIT ADC 500KSPS POWERWISE TSSOP16 |
| ADC78H90CIMT/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 8CH,500KSPS,12B 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 |
| ADC78H90CIMTX | 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 |
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