Posted on 10 March 2019

Programmable Power Technology offers Highest-In-Class Power Density and Efficiency with Versatile Programmable Functionality

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The increased complexity and sophistication of modern electronics in the field of networking, telecommunications, embedded systems, industrial control systems and automatic test equipment creates an ever increasing demand for advanced high performance power management systems.

By: Alan Elbanhawy, Simo Radovic and Jason Weinstein, Exar Corporation, California, USA

These systems require a host of features from precise programmable control loop parameters, fault monitoring and reporting to high power conversion efficiency and rail sequencing, all in the smallest possible footprint with uncompromising reliability. Devices like Exar’s XRP9710 and XRP9711 are changing the power management landscape by meeting all of these requirements plus a large variety of specialized features that deliver fully customizable solutions and a very fast design cycle every time.

The Challenge

The continuous push for smaller electronic equipment and appliances has resulted in power management applications that demand a wide range of specifications that dictate the use of multiple ICs and discrete components to meet all the requirements. Generally, these components are not perfectly matched for the application and hence some compromises must be made in the final design implementation. This also leads to larger PCB real estate to accommodate such designs leading to higher cost and potentially larger EMI due to trace parasitics ringing and ground planes bouncing in a larger size PCB. Achieving good efficiencies is an absolute requirement to achieve higher reliability and lower PCB temp rise; but this necessitates finding, sourcing and testing multiple power components like MOSFETs, MOSFET gate drivers, inductors and capacitors. This process can be a lengthy and costly activity and once successful, next leads to the challenging task of PCB layout of the powertrain which can take several iterations to reach an acceptable design. The lengthy process is a major investment in resources, time and cost that may affect time-to-market and/or the competitive positioning of the product.

XRP9710/XRP9711 Power Management modules

This family of power management modules takes on all of the above challenges head-on and offers an array of features that will meet the most demanding requirements and satisfy the most discriminating power design engineer. Figure 1 shows a simplified application schematic.

Simplified application schematic

Power Conversion Modulation Techniques

In order to maximize the efficiency over the entire load range, the power conversion architecture provides two types of modulation, Pulse Width Modulation (PWM) and a patented Pulse Frequency Modulation (PFM) with ultrasonic mode to guarantee that the lowest switching frequency does not drop down to the audible range. PFM provides very high efficiency at light loads and PWM provides high efficiency at medium to high loads. The control algorithm guarantees fully stable operation before, after and during transition from one mode to the other in both directions to guarantee a seamless operation over the entire load range.

Together with the PFM and PWM modes, the controller provides a patented Over Sampling (OVS) Feedback signal to guarantee excellent transient response.

Fast Transient Response

Figure 2 shows a simplified functional block diagram of the regulation loops for one output channel.

Block Diagram of Control Architecture

There are four separate parallel control loops; PWM, PFM, Ultrasonic, and Over Sampling (OVS). Each of these loops is fed by the Analog Front End (AFE) as shown at the left of the diagram. The AFE consists of an input voltage scalar, a programmable Voltage Reference (Vref) DAC, Error Amplifier, and a window comparator. Figure 3 shows the transient response.

Transient response 2A-6A

Power conversion efficiency

Figure 4 shows the efficiency for a 12V to 5V step down conversion, a sustained efficiency ≥ 90% over the range of 2.2A-6A and sustained efficiency ≥ 85% over the range of 0.25A-2.2A.

Efficiency measurement, Vin=12V, Vout=5V at 600KHz switching frequency; Vin=12V, Vout=1.8V at 600KHz switching frequency

Figure 5 shows the efficiency for a 12V to 1.8V step down conversion and figure 6 shows a thermal image of the module running at full power for the 12V to 1.8V case.

IR camera image, Vin=12V, Vout=1.8V at 600KHz switching frequency

Needless to say, the maximum module temperature will ultimately depend on the power losses and the available PCB copper area that acts as a heat-sink and helps radiate the heat, mitigating the maximum temperature. Practical PCB layout guidelines can be found in Application Note ANP-32.

Power Sequencing

Using the programming GUI supplied with all modules, all channels may be grouped together. Within a group, a user can specify the voltage ramp rate, the order in which the channels are powered up and any delays between channels. This applies to both the start-up and shut down allowing for maximum flexibility and total control of the order and the exact rate required for any given applications. Both sequential start-up/shutdown and simultaneous start-up/shutdown are supported, as illustrated in figures 7 and 8.

Sequential start-up and shut-down

Simultaneous start-up and shut-down

Fault management and protection

The XRP971x family offers an extensive array of fault reporting while allowing the user complete control over the system response by means of preprogramming or by allowing the host controller/CPU to react in real time to the reported fault through the use of the I2C bus:

  • Under Voltage Lockout (UVLO) monitors the input voltage and will cause the controller to shut-down if it drops below the preprogrammed level.
  • Over Voltage Protection (OVP) monitors the output voltage of all channels. This is a user defined parameter.
  • Over Temperature Protection (OTP). The controller will shut-down all channels if maximum temperature limit is exceeded
  • Over Current Protection. The limit is user defined and a user can choose one of three options for how to react to an OCP event: to shutdown the faulty channel, to shut down faulty channel and to perform auto restart of the channel, or to restart the chip.

Complete fault management details can be found in the datasheet (URL to be provided).

Advanced Feature Set

To round off the list of impressive performance features and advantages, the following is a brief description of some additional features to note:

  • The XRP9710/XRP9711 family of power management modules boasts the highest in-class power density in the industry with excellent package thermal resistance of both junction-to-case (θJC) and junction-to-ambient (θJA) in a 12mmx12mm Land Grid Array (LGA) package.
  • Very high reliability due to the fully optimized components with the proper design factor of safety criteria.
  • Design once and use multiple times in applications simply by reconfiguring the system software. This saves development time and R&D expense and results in optimum time-to-market and maintaining the product competitive positioning.
  • I2C and five GPIO ports for reporting and remote control functions by a host controller/CPU.
  • Perfect matching of the control IC and the power train components on a very small package outline of 12mm x 12mm:
    • Saves time sourcing, selecting and testing MOSFETs, inductors and capacitors etc.
    • Saves time on PCB layout and potential re-spins to optimize Efficiency, EMI and temperature rise of the application.
    • No need to procure and stock multiple parts, one part does it all.
  • Fully programmable parameters such as:
    • Output set point
    • Feedback compensation
    • Frequency set point
    • Under voltage lock out
  • Fully independent two/four channel multi-phase DPWM controllers.
  • Full operation and health reporting e.g. input/output voltages, output currents, die temperature etc. Using I2C and GPIOs, a system processor could be configured to log and analyze operating history, perform diagnostics and if required, take the supply off-line after making other system adjustments.
  • The module provides voltage tracking among the different channels.
  • An internal 5V LDO that can be used by the design engineer for any housekeeping tasks up to 135mA.
  • Differential voltage sensing is available in XRP9710. This allows for very precise output voltage set-point accuracy independent of PCB parasitic.


As we have seen, the XRP9710/11 is a family of versatile power management modules from Exar that offers significant advantages over other solutions on the market today. While the turn-around cycle for new products from concept to product release is getting shorter, this line of products takes away the time, expense and worry of power management system design and implementation. This allows design engineers to concentrate on the innovative aspects of their new products, and be free of concerns about the exacting performance specifications of their power management implementation.

Alan Elbanhawy:


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