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| 型号： | ISL28476 |
| 厂商： | Intersil Corporation |
| 英文描述： | 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) |
| 中文描述： | 双核和四微功耗单电源轨到轨输入和输出（RRIO）精密运算放大器（双/四通道，微功率，单电源，轨对轨输入/输出（RRIO）精密运放） |
| 文件页数： | 11/13页 |
| 文件大小： | 459K |
| 代理商： | ISL28476 |
11
FN6301.2
July 11, 2007
Applications Information
Introduction
The ISL28276 and ISL28476 are dual and quad BiCMOS
rail-to-rail input, output (RRIO) micropower precision
operational amplifiers. These devices are designed to
operate from a single supply (2.4V to 5.0V) or dual supplies
(±1.2V to ±2.5V) while drawing only 120
μ
A (ISL28276) of
supply current. This combination of low power and precision
performance makes these devices suitable for solar and
battery power applications.
Rail-to-Rail Input
Many rail-to-rail input stages use two differential input pairs,
a long-tail PNP (or PFET) and an NPN (or NFET). Severe
penalties have to be paid for this circuit topology. As the
input signal moves from one supply rail to another, the
operational amplifier switches from one input pair to the
other causing drastic changes in input offset voltage and an
undesired change in magnitude and polarity of input offset
current.
The ISL28276 and ISL28476 achieve input rail-to-rail without
sacrificing important precision specifications and degrading
distortion performance. The devices’ input offset voltage
exhibits a smooth behavior throughout the entire common-
mode input range. The input bias current versus the common-
mode voltage range gives us an undistorted behavior from
typically down to the negative rail to 10% higher than the V
+
rail (0.5V higher than V
+
when V
+
equals 5V).
Input Protection
All input terminals have internal ESD protection diodes to the
positive and negative supply rails, limiting the input voltage
to within one diode beyond the supply rails. Both parts have
additional back-to-back diodes across the input terminals. If
overdriving the inputs is necessary, the external input current
must never exceed 5mA. External series resistors may be
used as an external protection to limit excessive external
voltage and current from damaging the inputs.
Input Bias Current Compensation
The ISL28276 and ISL28476 contain an input bias
cancellation circuit which reduces the bias currents down to
a typical of 500pA while maintaining an excellent bandwidth
for a micro-power operational amplifier. The input stage
transistors are still biased with adequate current for speed
but the canceling circuit sinks most of the base current,
leaving a small fraction as input bias current.
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 ISL28276 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 ISL28276 and ISL28476 are dual and quad channel
op amps. If the application only requires one channel when
using the ISL28276 or less than 4 channels when using the
ISL28476, 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 38).
Proper Layout Maximizes Performance
To achieve the maximum performance of the high input
impedance and low offset voltage of the ISL28276 and
ISL28476, 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
39 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.
FIGURE 38. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
-
+
1/2 ISL28276
1/4 ISL28476
ISL28276, ISL28476
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL28476EVAL1Z | 功能描述:EVALUATION BOARD FOR ISL28476 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:- |
| ISL28476FAZ | 功能描述:IC OPAMP QUAD RRIO MCPWR 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 |
| ISL28476FAZ-T7 | 功能描述:IC OPAMP QUAD RRIO MCPWR 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 |
| ISL28478 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Dual Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Precision Op-Amp |
| ISL28478EVAL1Z | 功能描述:EVALUATION BOARD FOR ISL28478 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:- |
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