SNVSBU4E June 2022 – August 2024 LM5177
PRODUCTION DATA
The LM5177 features an internal error amplifier (EA) to regulate the output voltage. The output voltage gets sensed on the FB pin through external resistors, which determine the target or nominal output voltage. The reference for the EA builds the soft-start and analog output voltage tracking pin (SS/ATRK). The COMP pin is the output of the internal gm-stage and gets connected to the external compensation network. The voltage over the compensation network is the nominal value for the inner peak current control loop of the device.
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Use the following equations to calculate the external components:
External Feedback:
For most applications, TI recommends the following guidelines for bandwidth selection of the compensation.
The hard limit of the bandwidth (f(BW)) is the right half plane zero of the boost operation:
The maximum recommended bandwidth must be within the following boundaries:
The compensation zero (fCZ) must be placed in relation to the dominating pole of the boost.
Due to the precise implementation of the error amplifier, the voltage on the LM5177 COMP pin is accurately reflecting the nominal peak current value of the inductor. Figure 7-14 shows the control V/I-characteristics of the error amplifier in FPWM mode. Use this as a guidance for applicative designs where you need to manipulate the inner current loop regulation.