NDCU-21 NDCU21 机体应用于驱动控制单元

NDCU-21 NDCU21 机体应用于驱动控制单元 

OPA858采用低压、高速、BiCMOS工艺制造。内部结击穿
这些小型几何器件的电压较低，因此，所有器件引脚都受到内部保护
电源的ESD保护二极管如图48所示。之间有两个反并联二极管
放大器的输入，在过量程或故障条件下箝位输入。
图48内部ESD结构
9.3.2反馈引脚
OPA858引脚布局经过优化，以小化寄生电感和电容，这在高速模拟设计中至关重要。FB引脚（引脚1）内部连接到放大器的输出。FB引脚为
通过非连接（NC）引脚（引脚2）与放大器的反相输入（引脚3）分离。NC引脚必须为
左浮动。这种引脚布局有两个优点：
1.反馈电阻器（RF）可连接在封装同一侧的FB和IN–引脚之间（参见
图49）。
2.NC引脚产生的隔离通过以下方式小化FB和IN引脚之间的电容耦合：
增加了销之间的物理间隔。
图49 FB和IN引脚之间的射频连接
频率（Hz）
开环增益（dB）
-15
0
15
30
45
60
75
90
100k 1M 10M 100M 1G 10G
D204
40qC处的AOL
美国在线25qC
AOL at+125qC
频率（Hz）
开环增益（dB）
-15
0
15
30
45
60
75
90
100k 1M 10M 100M 1G 10G
D205
AOL（  V）
AOL（典型）
AOL（  V）
17
OPA858
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产品文件夹链接：OPA858
版权所有©2018，德克萨斯仪器公司提交文件反馈
功能描述（续）
9.3.3宽增益带宽积
图10显示了OPA858的开环幅度和相位响应。计算增益带宽
通过确定AOL为60 dB的频率并将该频率乘以
系数1000。AOL响应中的第二个极点出现在幅值超过0 dB之前，并且
合成相位裕度小于0°。这表示增益为0dB（1V/V）时的不稳定性。放大器不是
单位增益稳定被称为失补偿放大器。与单位增益稳定放大器相比，失补偿放大器通常具有更高的增益带宽积、更高的转换速率和更低的电压噪声
静态功耗相同。
图50显示了作为温度函数的OPA858的开环幅度（AOL）。结果表明：
温度变化小。OPA858的相位裕度配置为7 V/V的噪声增益（16.9
dB）在温度范围内接近55°。类似地，图51显示了OPA858的AOL幅度为
工艺变化的函数。结果显示了标称工艺角和变化的AOL曲线
标称值的一个标准偏差。模拟结果表明相位裕度小于1°

NDCU-21 NDCU21 机体应用于驱动控制单元 

NDCU-21 NDCU21 机体应用于驱动控制单元 

The OPA858 is fabricated on a low-voltage, high-speed, BiCMOS process. The internal, junction breakdown
voltages are low for these small geometry devices, and as a result, all device pins are protected with internal
ESD protection diodes to the power supplies as Figure 48 shows. There are two antiparallel diodes between the
inputs of the amplifier that clamp the inputs during an overrange or fault condition.
Figure 48. Internal ESD Structure
9.3.2 Feedback Pin
The OPA858 pin layout is optimized to minimize parasitic inductance and capacitance, which is critical in highspeed analog design. The FB pin (pin 1) is internally connected to the output of the amplifier. The FB pin is
separated from the inverting input of the amplifier (pin 3) by a no connect (NC) pin (pin 2). The NC pin must be
left floating. There are two advantages to this pin layout:
1. A feedback resistor (RF) can connect between the FB and IN– pin on the same side of the package (see
Figure 49) rather than going around the package.
2. The isolation created by the NC pin minimizes the capacitive coupling between the FB and IN– pins by
increasing the physical separation between the pins.
Figure 49. RF Connection Between FB and IN– Pins
Frequency (Hz)
Open-Loop Gain (dB)
-15
0
15
30
45
60
75
90
100k 1M 10M 100M 1G 10G
D204
AOL at 40qC
AOL at 25qC
AOL at +125qC
Frequency (Hz)
Open-Loop Gain (dB)
-15
0
15
30
45
60
75
90
100k 1M 10M 100M 1G 10G
D205
AOL (V)
AOL (Typ.)
AOL (V)
17
OPA858
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Product Folder Links: OPA858
Copyright © 2018, Texas Instruments Incorporated Submit Documentation Feedback
Feature Description (continued)
9.3.3 Wide Gain-Bandwidth Product
Figure 10 shows the open-loop magnitude and phase response of the OPA858. Calculate the gain bandwidth
product of any op amp by determining the frequency at which the AOL is 60 dB and multiplying that frequency by
a factor of 1000. The second pole in the AOL response occurs before the magnitude crosses 0 dB, and the
resultant phase margin is less than 0°. This indicates instability at a gain of 0 dB (1 V/V). Amplifiers that are not
unity-gain stable are known as decompensated amplifiers. Decompensated amplifiers typically have higher gainbandwidth product, higher slew rate, and lower voltage noise, compared to a unity-gain stable amplifier with the
same amount of quiescent power consumption.
Figure 50 shows the open-loop magnitude (AOL) of the OPA858 as a function of temperature. The results show
minimal variation over temperature. The phase margin of the OPA858 configured in a noise gain of 7 V/V (16.9
dB) is close to 55° across temperature. Similarly Figure 51 shows the AOL magnitude of the OPA858 as a
function of process variation. The results show the AOL curve for the nominal process corner and the variation
one standard deviation from the nominal. The simulated results suggest less than 1° of phase margin