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| 型号： | ISL28278 |
| 厂商： | Intersil Corporation |
| 英文描述： | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)运放) |
| 中文描述： | 双核和四微功耗单电源轨到轨输入和输出（RRIO）运算放大器（双/四通道，微功率，单电源，轨对轨输入/输出（RRIO）运放） |
| 文件页数： | 11/13页 |
| 文件大小： | 496K |
| 代理商： | ISL28278 |
11
FN6145.2
July 11, 2007
Rail-to-Rail Output
A pair of complementary MOSFET devices are used to achieve
the rail-to-rail output swing. The NMOS sinks current to swing
the output in the negative direction. The PMOS sources current
to swing the output in the positive direction. Both parts, with a
100k
Ω
load, will typically swing to within 4mV of the positive
supply rail and within 3mV of the negative supply rail.
Enable/Disable Feature
The ISL28278 offers two EN pins (EN_A and EN_B) which
disable the op amp when pulled up to at least 2.0V. In the
disabled state (output in a high impedance state), the part
consumes typically 4μA. By disabling the part, multiple parts
can be connected together as a MUX. The outputs are tied
together in parallel and a channel can be selected by the EN
pins. The loading effects of the feedback resistors of the
disabled amplifier must be considered when multiple
amplifier outputs are connected together. The EN pin also
has an internal pull-down. If left open, the EN pin will pull to
the negative rail and the device will be enabled by default.
Using Only One Channel
The ISL28278 and ISL28478 are dual and quad channel
op amps. If the application only requires one channel when
using the ISL28278 or less than 4 channels when using the
ISL28478, the user must configure the unused channel(s) to
prevent them from oscillating. The unused channel(s) will
oscillate if the input and output pins are floating. This will
result in higher than expected supply currents and possible
noise injection into the channel being used. The proper way
to prevent this oscillation is to short the output to the
negative input and ground the positive input (as shown in
Figure 36).
Proper Layout Maximizes Performance
To achieve the maximum performance of the high input
impedance and low offset voltage of the ISL28278 and
ISL28478, care should be taken in the circuit board layout.
The PC board surface must remain clean and free of
moisture to avoid leakage currents between adjacent traces.
Surface coating of the circuit board will reduce surface
moisture and provide a humidity barrier, reducing parasitic
resistance on the board. When input leakage current is a
concern, the use of guard rings around the amplifier inputs
will further reduce leakage currents. Figure
37 shows a
guard ring example for a unity gain amplifier that uses the
low impedance amplifier output at the same voltage as the
high impedance input to eliminate surface leakage. The
guard ring does not need to be a specific width, but it should
form a continuous loop around both inputs. For further
reduction of leakage currents, components can be mounted
to the PC board using Teflon standoff insulators.
Example Application
Thermocouples are the most popular temperature-sensing
device because of their low cost, interchangeability, and
ability to measure a wide range of temperatures. The
ISL28X78 (Figure 38) is used to convert the differential
thermocouple voltage into single-ended signal with 10X gain.
The ISL28X78's rail-to-rail input characteristic allows the
thermocouple to be biased at ground and the amplifier to run
from a single 5V supply.
.
Current Limiting
The ISL28278 and ISL28478 have no internal current-
limiting circuitry. If the output is shorted, it is possible to
exceed the Absolute Maximum Rating for output current or
power dissipation, potentially resulting in the destruction of
the device.
Power Dissipation
It is possible to exceed the +150°C maximum junction
temperatures under certain load and power-supply
conditions. It is therefore important to calculate the
maximum junction temperature (T
JMAX
) for all applications
to determine if power supply voltages, load conditions, or
package type need to be modified to remain in the safe
operating area. These parameters are related in Equation 1:
FIGURE 36. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
-
+
1/2 ISL28278
1/4 ISL28478
IN
V+
FIGURE 37. GUARD RING EXAMPLE FOR UNITY GAIN
AMPLIFIER
HIGH IMPEDANCE INPUT
-
+
ISL28X78
5V
+
V+
V-
K TYPE
THERMOCOUPLE
10k
Ω
R
3
10k
Ω
R
2
R
4
100k
Ω
R
1
100k
Ω
410μV/°C
FIGURE 38. THERMOCOUPLE AMPLIFIER
T
JMAX
T
MAX
θ
JA
xPD
MAXTOTAL
(
)
+
=
(EQ. 1)
ISL28278, ISL28478
相关PDF资料 |
PDF描述 |
|---|---|
| ISL28478 | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)运放) |
| ISL28286 | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Precision Op Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)精密运放) |
| ISL28486 | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Precision Op Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)精密运放) |
| ISL28288 | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)运放) |
| ISL28488 | Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp(双/四通道，微功率，单电源，轨对轨输入/输出(RRIO)运放) |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL28278_07 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp |
| ISL28278EVAL1Z | 功能描述:EVALUATION BOARD FOR ISL28278 RoHS:是 类别:编程器，开发系统 >> 评估板 - 运算放大器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- |
| ISL28278FAZ | 功能描述:IC OPAMP DUAL RRIO PREC 16-QSOP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 其它有关文件:Automotive Product Guide 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 放大器类型:通用 电路数:1 输出类型:满摆幅 转换速率:3 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:1pA 电压 - 输入偏移:70µV 电流 - 电源:2.5mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):2.7 V ~ 5.5 V，±1.35 V ~ 2.75 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SOT-23-6 供应商设备封装:SOT-6 包装:Digi-Reel® 其它名称:MAX4475AUT#TG16DKR |
| ISL28278FAZ-T7 | 功能描述:IC OPAMP DUAL RRIO PREC 16-QSOP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 其它有关文件:Automotive Product Guide 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 放大器类型:通用 电路数:1 输出类型:满摆幅 转换速率:3 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:1pA 电压 - 输入偏移:70µV 电流 - 电源:2.5mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):2.7 V ~ 5.5 V，±1.35 V ~ 2.75 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SOT-23-6 供应商设备封装:SOT-6 包装:Digi-Reel® 其它名称:MAX4475AUT#TG16DKR |
| ISL28278FAZ-TZ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Intersil Corporation 功能描述: |
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