ALM2403-Q1
ZHCSMT3A –NOVEMBER 2020 –REVISED MARCH 2023
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8 Application and Implementation
备注
以下应用部分中的信息不属于TI 器件规格的范围，TI 不担保其准确性和完整性。TI 的客 户应负责确定
器件是否适用于其应用。客户应验证并测试其设计，以确保系统功能。
8.1 Application Information
The ALM2403-Q1 is a dual-power op amp with performance and protection features that are optimal for many
applications. For op amps, there are many general design consideration that must be taken into account. The
following subsections describe what to consider for most closed-loop applications. 节 8.2 gives a specific
example of the ALM2403-Q1 being used in a resolver application.
8.1.1 Capacitive Load and Stability
The ALM2403-Q1 is designed for applications where driving a capacitive load is required. As with all op amps,
specific instances can occur where the ALM2403-Q1 device can become unstable. The particular op-amp circuit
configuration, layout, gain, and output loading are some of the factors to consider when establishing whether or
not an amplifier is stable in operation. An op amp in a unity-gain (1-V/V) buffer configuration that drives a
capacitive load exhibits a greater tendency to become unstable compared to an amplifier operated at a higher-
noise gain. The capacitive load, in conjunction with the op-amp output resistance, creates a pole within the
feedback loop that degrades the phase margin. The degradation of the phase margin increases as the
capacitive loading increases. When operating in a unity-gain configuration, the ALM2403-Q1 remains stable with
a pure capacitive load up to approximately 30 pF. Increasing the amplifier closed-loop gain allows the amplifier to
drive increasingly larger capacitance. This increased capability is evident when observing the overshoot
response of the amplifier at higher voltage gains.
One technique for increasing the capacitive load drive capability of the amplifier operating in a unity-gain
configuration is to insert a small resistor (RS; typically, 100 mΩto 10 Ω) in series with the output, as shown in 图
8-1. This resistor significantly reduces the overshoot and ringing associated with large capacitive loads.
V+
RS
œ
VOUT
CL
+
RL
+
VIN
œ
图8-1. Capacitive Load Drive
8.2 Typical Application
High-power ac and brushless dc (BLDC) motor-drive applications need position feedback to efficiently and
accurately drive the motor. Position feedback can be achieved by using optical encoders, hall sensors, or
resolvers. Resolvers are the main choice when environmental or longevity requirements are challenging and
extensive.
A resolver acts as a transformer with one primary coil and two secondary coils. The primary coil, or excitation
coil, is located on the rotor of the resolver. As the rotor of the resolver spins, the excitation coil induces a current
into the sine and cosine sensing coils. These coils are oriented 90 degrees from one another, and the voltage
from the sine and cosine coils is translated into a vector position by the microcontroller or resolver-to-digital
converter chip.
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Product Folder Links: ALM2403-Q1
English Data Sheet: SBOSA37
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