LM5008MM

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DC-DC Switching Regulators are a type of power management integrated circuit (PMIC) used to regulate the voltage supply of external components. The LM5008MM is a DC-DC Converter Step Down Current Mode Controller feature integrated high and low-side switches, as well as a unique architecture, to allow buck/boost controllable operation over a wide output voltage range. This article will discuss the application fields and working principles of the LM5008MM.

Application Field

The LM5008MM is designed for applications that require a flexible voltage regulation, such as digital TV and display, industrial and communication equipment, automotive, and network power system. It operates from an input voltage of 4.5V to 40V, and provides an output voltage from 0.8V to 20V. Furthermore, the device looks to provide a fast response to input voltage changes, offers lossless current and voltage sensing, as well as offers low noise due to the fMax clock frequency up to 2MHz.

Operation Principle and Block Diagram

The LM5008MM works on the principle of constant on-time control, with a current sense comparator and an error amplifier. The internal error amplifier acts as a reference regulator. The output of the error amplifier is compared to the monitored current, and the difference is fed back to the controller, resulting in a fast and efficient voltage regulation. As depicted in the following block diagram, the LM5008MM comprises of the following key components:

• An internal oscillator
• An internal logic Engine
• An error amplifier
• A current sense comparator
• A power stage

The internal oscillator clocks the internal Logic Engine and turns the control signal on and off. The internal error amplifier monitors the output voltage, and the internal current sense comparator to reference the current. The power stage then turns on and off the switched using the current and voltage controlled signals, allowing the output voltage to be maintained.

The following figure shows the block diagram for the LM5008MM.

External Components

The device provides two external components, namely, a resistor to set the compensation for the error amplifier and a capacitor connected to the current sense input. The resistor is used to set the desired compensation for the error amplifier, while the capacitor is used to set the desired current sense in parallel to the power stage. The combination of the two controls the desired current sense and compensations for the input voltage changes.

Conclusion

The LM5008MM is a DC-DC Converter Step Down Current Mode Controller designed to provide a fast response to input voltage changes, and adapted to applications that require a flexible voltage regulation. The device looks to provide lossless current and voltage sensing, as well as low noise operation due to its wide fMax clock frequency up to 2MHz.

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