LM3524DN/NOPB

LM3524DN/NOPB Application Field and Working Principle

Power management integrated circuit (PMIC) is one of the most important electrical components for regulating the power in a electronic system. Out of the broad range of categories of PMICs, the most-widely used one is the voltage regulators, which basically control the output voltage and current of a device to balance the energy input and output. Among various power management integrated circuits, DC DC switching controllers are used as a type of voltage regulator devices and they provide a economical, reliable and efficient solution to the power design in many electronics systems. In this article, the LM3524DN/NOPB, a DC-DC switching controller manufactured by Texas Instruments, will be discussed in detail – its application field and the working principle.

LM3524DN/NOPB is a monolithic integrated switching control circuit that is produced by Texas Instruments. It is specially designed for a wide range of off-line and DC-DC converter applications and possess many excellent features such as an enhanced transient response, low stand-by current, simplified synchronization requirements, as well as a wide operating voltage of 7V to 40V. The LM3524DN/NOPB switching controller is also capable of efficiently converting an unregulated input voltage into an adjustable output voltage in the range of 0.8V to 37V with an output load current of up to 1.5A. This device also features a hiccupovercurrent protection mode and a wide operating temperature range of - 55℃ to +125℃ making it well-suitable for high-power off-line applications such as automotive, power supplies and solar panel converters.

Moreover, the LM3524DN/NOPB is generally applied in power inverters, resonant converters, AC-DC power supplies, LED driver and so on. It is also extensively used in motor control applications like brushless DC fan and pump motor controllers, solar panel controllers and PFC controllers.

Let’s look into the device’s internal operation. In a general DC-DC converter application, LM3524DN/NOPB operates according to the constant-frequency, current-mode switching principle. It features an oscillator which tunes the chip’s switching frequency with a half-bridge topology having external N-MOSFETs as power switches and a compensation network. As illustrated in the diagram below, the chip’s current-sense input (CS) monitor the output current by dividing out some of the current through the current transformer, then it is averaged and compared to the internal reference. This allows the device to regulate output current and maintain it at the intended level. Meanwhile, the voltage-sensing input (FB) functions similarly to sense the output voltage and it produces a feedback signal that is compared to an internal reference. By regulating the on-time of the power switches, the output voltage can be maintained at the expected level.



The LM3524DN/NOPB is also capable of regulating output current with its current-limit comparator, which senses voltage changes across a current sense resistor. When the current sense resistor exceeds the internal reference voltage, the switch output is disabled in the current limit mode. And when the load current increases to a point where the voltage across the current sense resistor is above 1V, the current limit comparator will cause the switch to return to normal operation.

To sum up, the LM3524DN/NOPB is a low-cost and cost-effective DC-DC switching controller with great efficiency and stability. It is suitable for many electronic systems, like motor control, power inverters, LED driver and solar panel controllers, etc. Furthermore, its features such as adjustable current/voltage sensing, current limit, low stand-by current and wide operating temperature range, make it an optimal choice for power management design.