Figure 1: Inside the ISL8215M power module
The DC/DC buck converter is one of the most popular and widely used power supply topologies, finding applications in industrial, servers, telecom, and automotive sectors. The non-isolated buck converter also sees increasing use as a point-of-load (POL) solution to deliver power from a DC bus to individual POLs. It steps down the DC bus voltage to lower regulated output voltages. An ideal POL solution should be capable of supporting a wide range of input voltages while providing a stable operation at small duty cycles. For applications constrained by board space, a compact, higher power density design is required, and to minimize power losses and provide cost savings, high conversion efficiency is needed.
Discrete POL solutions involve careful selection of components, including inductor, MOSFETs and capacitors, and that requires an experienced power supply designer. In addition, the placement of the components on the PCB is crucial since they have a direct correlation with efficiency, noise and thermal performance. Compensation elements must be carefully selected to keep the converter stable across all operating conditions. This is a cumbersome task, especially if the system has multiple POL power rails. All of these factors can lead to longer design cycles and increased cost of ownership.
Power Module: A Simplified Approach
Power modules provide an alternative to the lengthy and arduous process of discrete power supply design by integrating all of the key components inside the package. Figure 1 shows that a power module is a complete power supply in a condensed package that requires only a few external components to function.
A power module includes the high-side and low-side MOSFETs, inductor, controller, and the compensation network. The customer typically only needs to select the input and output capacitors, along with a few resistors to complete the power supply design. Power modules offer several advantages:
- Higher integration offers increased power density to occupy less board space
- Shorter development times lead to reduced cost of ownership
- Higher reliability due to detailed manufacturer characterization
- Efficient thermal management due to better packaging technology
- Simplified PCB layout and reduced design complexity due to fewer external components
- Easier manufacturing and assembly process with direct placement on application boards Achieving High Power Density
Achieving High Power Density
The ISL8215M is a first of its class single-phase power module supporting a wide input/output voltage range, while delivering up to 180W output power from a small 13mm x 19mm thermally enhanced High Density Array (HDA) package. This makes it one of the highest power density POL solutions. The input voltage can vary from 7V to 42V and the output voltage is adjustable from 0.6V to 12V, while allowing a programmable switching frequency from 300kHz to 2MHz.
As seen in Figure 2, the ISL8215M requires only a few external resistors and capacitors to form a complete power supply solution. Internal compensation networks are implemented to stabilize the converter and achieve an optimal transient response across the full range of input and output operating conditions.
Figure 2: ISL8215M typical application circuit
The ISL8215M is able to operate from a 42V input rail, providing customers with extra input voltage safety margin. This makes it ideal for industrial applications. It is able to achieve a high conversion ratio (42V input to 1.2V/3.3V output) by employing valley current mode control with an input voltage feedforward ramp. This eliminates the need for blanking time (as is the case with peak current mode), making it possible to control very narrow on-time pulses and provide excellent transient performance.
The ISL8215M is a highly characterized, reliable power module, which requires a minimal number of external components for developing a complete power supply solution. Its advanced packaging technology provides an excellent thermal performance over a wide range of operating temperatures. And, its high power density in a small footprint is made possible due to the high efficiency of the module, which reduces power dissipation and increases the current rating of the device. A wide output voltage range from 0.6V to 12V enables the module to be an efficient POL solution, while also allowing for an intermediate 12V/5V bus voltage generation.