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“System designers are being asked to produce smaller, more efficient power solutions to meet the high power demands of SoCs and FPGAs across all industries. In advanced Electronic systems, the footprint of the power supply package is critical because the power supply must be placed near the SoC or its peripherals such as DRAM or I/O devices. In portable instruments, such as handheld barcode scanners or medical data logger systems, space is more compact.
System designers are being asked to produce smaller, more efficient power solutions to meet the high power demands of SoCs and FPGAs across all industries. In advanced electronic systems, the footprint of the power supply package is critical because the power supply must be placed near the SoC or its peripherals such as DRAM or I/O devices. In portable instruments, such as handheld barcode scanners or medical data logger systems, space is more compact.
Designers face more than just finding a regulator that can fit in a limited space. The requirements for compact solutions often conflict with other advanced electronics requirements: reliable design, high efficiency, large conversion ratio, high power, small size, and good thermal performance. Many of these requirements require trade-offs in other areas, which present designers with a difficult and time-consuming optimization problem. The LTC3636 is designed to simplify the designer’s task with a dual 6 A buck regulator that consumes very low standby current in shutdown and operates at frequencies up to 4 MHz at both full and light loads Has high efficiency.
Small size and 4 MHz switching frequency
It is a ubiquitous fact in power supply design that the allotted application space is small. The volume and power density of DC-DC converters are often limited by bulky magnetic components, input/output capacitors, EMI filters, and heat sinks. In a buck power converter, size and efficiency are often not compatible: the size of the Inductor and output capacitor can be significantly reduced by increasing the switching frequency, but high frequency operation increases the switching losses of the inductor and switch. This in turn complicates thermal management in tight spaces.
The LTC3636 is a dual, 6 A per output, high efficiency monolithic step-down regulator capable of operating from input supply voltages up to 20 V. The programmable switching frequency can be set up to 4 MHz. High switching frequency significantly reduces the size and value of inductors and capacitors, but unlike many high frequency solutions, the LTC3636 also maintains high efficiency, allowing the use of some ultra-small ferrite inductors with lower AC and DC losses . The two channels operate 180° out of phase, and the switching pulses are interleaved for lower ripple, which in turn reduces the input capacitance value.
The dual buck converter in Figure 1 operates at 4 MHz and uses very small voltages and capacitors. Efficiency and thermal performance are shown in Figure 2. Thermal images show a temperature rise below 40°C with natural convection at room temperature at VIN = 5 V.
Figure 1.4 MHz dual buck regulator provides a compact solution.
Figure 2. Efficiency curve (left) and thermal image (right). Condition: VIN = 5 V, natural convection.
High-efficiency power conversion over the entire load range
High efficiency over the entire load range is critical for portable equipment and automotive applications. Under heavy loads, the power loss should be small for the Circuit to operate reliably. In order to achieve this goal, the circuit design under heavy load can be optimized, and combined with the TMON pin for thermal monitoring, stable thermal protection is designed to achieve reliable thermal management, so that heat sink or forced airflow cooling is not required.
High efficiency at light loads is also important for battery-powered systems to extend runtime between charges. In addition, low shutdown power consumption is the key to avoiding leakage in battery-powered systems. Also weighing efficiency at heavy or light loads often limits the performance of a common power supply overall solution.
The LTC3636 regulator features low quiescent current for high efficiency at output voltages up to 5 V. The LT3636-1 variant extends the VOUT range to 12 V. This buck regulator is capable of operating from an input voltage range of 3.1 V to 20 V while delivering up to 6 A of output current per channel. Figure 3 shows a high-efficiency solution, while Figure 4 shows that its measured efficiency remains high over the entire operating range.
Figure 3. High-efficiency dual-channel buck regulator.
Figure 4. Efficiency curves for VOUT = 5 V and 3.3 V.
Figure 5.12 Schematic of the A/0.85 V regulator and load transient.
Configurable for dual-phase single output up to 12 A
The proliferation of advanced SoC and FPGA electronic systems in automotive, transportation and industrial applications requires higher performance power supplies. The power demands of these advanced SoCs continue to increase, and solutions based on traditional PWM controllers and MOSFETs must employ monolithic regulators for smaller size, higher current capability and higher efficiency. The LTC3636 is designed to meet these advanced SoC power requirements while meeting the SoC’s solution size and thermal constraints. Figure 5a shows a schematic of a two-channel parallel power supply, delivering up to 12 A at 0.85 V. When VIN is 3.3 V, the peak efficiency of 12 A output load is 87%. The load transient is shown in Figure 5b. In this design, the FB1 and FB2 pins are connected together, as are the RUN1 and RUN2 pins. The ITH1 and ITH2 pins are tied together and external compensation is set to minimize current mismatch and transients in steady state.
Industrial and automotive applications require higher levels of intelligence and automation, as well as more detection capabilities, resulting in an explosion in the number of electronic systems and increasing demands on power performance. The LTC3636 simplifies system design with two high-efficiency power rails, each capable of supporting up to 6 A and consuming very low standby current during shutdown. The LTC3636 is available in a thermally enhanced, low profile 28-pin, 4 mm × 5 mm QFN package. Built-in over-temperature protection improves reliability. The chip provides a user-selectable mode input that allows the user to trade off output ripple against light-load efficiency. Burst Mode® provides the highest efficiency at light loads, while forced continuous mode provides the lowest output ripple.
About the Author
Zhongming Ye is a senior applications engineer for power products at Analog Devices in Milpitas, California, USA. He has been with Linear Technology (now part of Analog Devices) since 2009, providing application support for a variety of different products including buck, boost, flyback and forward converters. His focus in power management includes high-efficiency, high-power-density, and low-EMI high-performance power converters and regulators for automotive, medical, and industrial applications. Before joining Linear Technology, he spent three years at Intersil working on PWM controllers for isolated power products. He holds a PhD in Electrical Engineering from Queen’s University, Kingston, Canada. Zhongming is a senior member of the IEEE Power Electronics Society. Contact information:[email protected]