ISL8272M - 50A Single Channel Digital PMBus™ Step-Down Power Module
Welcome to the ISL8272M presentation. The ISL8272M is part of Intersil’s family of fully encapsulated power management modules. This presentation will give you a brief overview of the device feature set and performances.
50A Single Channel Digital PMBus Step-Down Power Module
The ISL8272M is a complete DC/DC step-down power supply solution encapsulated in a single package. Operating from the industry standard 5V or 12V power rails, it is capable of providing up to 50A of continuous output current, can be programmed to output voltages as low as 0.6V and offers better than 90% efficiency on most conversion ratios. Its unique ChargeMode control loop architecture requires no external compensation, can operate up to 1MHz and allows the ISL8272M to react to any output current load step within one single cycle.
The ISL8272M implements a standard PMBus compliant interface, providing not only a complete customization of all operating parameters but also advanced telemetry capabilities for system health report and monitoring. In addition to its digital interface, the ISL8272M offers a pin-strap mode, allowing most common operating parameters to be set through external resistors, virtually eliminating the need for any PMBus commands to operate. The ISL8272M is not only a standalone device, multiple modules can be combined to provide up to 200A in a single power rail thanks to the ISL8272M active current sharing mode. In this configuration, multi-phase or phase spreading operations are supported. Built-in advanced protections ensure safe operations under abnormal operating conditions.
The ISL8272M incorporates, in a small 18mm x 23mm x 7.5mm footprint thermally enhanced HDA package, all of the main power components such as the controller, power FETs and inductors. It only requires a few external components to operate, making it a solution of choice for an easy design-in without sacrificing performance and reliability.
Ease of Design – Typical Standalone Application
The typical application diagram shown here is a good illustration of how easy the ISL8272M is to design in. Only a few external components are required to operate; input and output capacitors, decoupling capacitors and pin-strap resistors are the only required components to be chosen. The ISL8272M provides precise guidance to select these components based on the exact operating mode and performance expected.
The PowerNavigator design and configuration software fully supports the ISL8272M providing the power designer with an intuitive and easy to use interface, reducing the development time for the overall power train solution. PowerNavigator is a free download from our website.
Configuration, Control and Telemetry
The system has two options to control operations of the ISL8272M. Both options can be used exclusively or in conjunction with one another as long as the control and/or configuration instructions do not conflict.
A set of external pin-strap resistors allows configuring the device for standard operations when typical values are required for a subset of operating parameters such as output voltage and switching frequency, among others. In this mode, no communication through the PMBus is required and usage can be made of the dedicated control pins which provide a direct mean to enable the device, perform some margining testing and monitor power good status.
In order to take full advantage of the ISL8272M advanced power management features and telemetry capabilities however, PMBus communication is required. All configuration parameters can be configured and adjusted through standard registers settings and all critical operating parameters can be monitored in real time. This monitoring function, known as telemetry, enables the system to closely monitor the power rail and report a health status of the system. This is particularly critical when powering expensive DSPs and FPGAs, a natural application for the ISL8272M.
The Intersil proprietary ChargeMode control loop architecture combined with high performance on-board FETs allows the ISL8272M to operate at better than 90% efficiency on most voltage conversion ratios. The efficiencies can even reach about 95% on a typical 12V to 3.3V conversion for currents above 25A. This is a critical performance that reduces the thermal stress on the device and facilitates thermal management of the overall system. In addition, the ISL8272M can be configured to operate at up to 1MHz with its internal clock providing extreme flexibility when optimizing efficiency and transient response performances.
Fast Transient Response to Output Load Steps
The ISL8272M control loop architecture not only provides flexibility in selecting the operating switching frequency, it also provides for an extremely fast control loop response to any output current load steps. The absence of any compensation components reduces the feedback loop response to a minimum and the ISL8272M is capable of reacting to an output load step within one single clock cycle. Additional digital knobs, addressable through the PMBus, allows for fine customization of the transient response.
This is a key benefit for the power designer. The ISL8272M does not require additional output capacitance to reduce the output voltage variations following a load step. Hence, the external capacitors footprint is kept to a minimum.
Soft-Start/Stop, Sequencing and Margining
A 50A capable power rail, or even more in a multi-module implementation, requires advanced and precise start, stop and sequencing timing management. The ISL8272M is fully customizable with programmable soft-start and soft-stop delays and ramps. A pin-strap resistor can set the delay and ramp times to typical values while dedicated registers, accessible through the PMBus, provide for finer resolution settings and fully independent control of the start and stop sequences.
Furthermore, when multiple power rails are present, the illustrations on the right show four rails; it may be important to precisely control the order in which the various rails power up; this is known as sequencing. The ISL8272M provides advanced controls for sequencing through the Intersil exclusive Digital-DC (DDC) Bus. This DDC Bus allows interconnection of all Intersil point-of-load solutions supporting the DDC Bus and configuration of each point-of-load in prequel/sequel implementation to precisely control the order at which the power rails are enabled.
Multi-Phase/Multi-Module and Digital-DC™ Bus Operation
We have briefly touched on the capability of the ISL8272M to be implemented in a multi-module configuration; ultimately allowing this device to provide up to 200A capable power rail in a current sharing mode.
At this point, it is important to note that as a standalone 50A capable device, the ISL8272M already operates in a 180º dual phase mode. When used in a current sharing, multi-module application, up to four parallel modules, operations can and often need to be spread over multiple phases. This drastically reduces stress on the input filter of the converters. The ISL8272M automatically synchronizes all modules to the same clock and adjusts the phase offset between converters, when placed in a current sharing configuration. Precise phase offset control is also possible through the PMBus.
In a multi-phase/multi-module configuration, it is also critical to precisely balance the current each converter provides to the common power rail. This helps to distribute the thermal load and power losses equally across the modules. The ISL8272M, through the DDC Bus, provides an active current balancing between all converters placed in current sharing mode. In that mode, a reference module sets the reference output current while all other member modules adapt their output to either increase, as shown in the illustration, or decrease their output current to align with the reference achieving the precise balancing.
This feature is permitted through the DDC Bus which interconnects DDC Bus enabled devices. This DDC Bus also permits advanced power management operations and settings at the system level. In addition to the current balancing functions and, as seen previously, the advanced sequencing functions it permits, the DDC Bus also provides fault reporting and handling between modules.
Faults Reporting and Handling
In addition to a dedicated power flag that can be used on a system level interruption, the ISL8272M possesses an extensive array of built-in protections covering monitoring for both the input and output voltages, output current and internal temperature. Default settings and handling apply when used in a pin-strap configuration; usage of the PMBus allows for full customization of warning and maximum threshold levels as well as reporting and handling configuration. Specifically, each fault reporting can selectively be reported to other devices sharing the same DDC Bus and trigger either a full shutdown of the faulty power rail or attempt timed restarts.
Package Has Unmatched Thermal Performance
The high density array package, or HDA package, is unique Intersil packaging technology combining excellent thermal performance with a compact and low height profile. This package is based on a copper leadframe which provides for direct heat transfer to the exposed pads and onto the PCB board. This over-molded package is suitable for pick and place equipment, hence making it a convenient choice for automated manufacturing facilities.
Thanks to this packaging technology, the ISL8272M can operate at a maximum output current up to 60 °C of ambient temperature without requiring any air flow.
ISL8272M Evaluation Boards
Evaluation boards are readily available for the ISL8272M. Two options are offered; one is configured as a single module, hence capable of an output current of 50A maximum, while the second option is configured as a triple module in current sharing mode, capable of 150A output current maximum.
Key Benefits and Summary
The ISL8272M is a complete DC/DC step-down power supply solution encapsulated in a single package. Fully addressable through its PMBus interface, the ISL8272M provides the system with full customization, advanced power management functionalities and overall high performance in a very easy design-in solution.
ISL8270M/71M/72M (50A) Digital Power Modules
Last but not least, be aware that the ISL8272M is part of a greater family of devices, namely the ISL8270M and ISL8271M. This family of devices shares the same feature set and provides three complete DC/DC step-down power supply solutions rated at an output current capability of 25A, 33A and 50A. In addition, the ISL8270M 25A solution and ISL8271M 33A solution share the same footprint.
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