Q. What difference does Hyperlight Load make to a power module and how does HyperSpeed help drive an application?
A. Hyperlight Load is a trademark Micrel circuitry that enables high power efficiency during light load conditions. The controller integrated circuit (IC) goes into a discontinuous mode to maintain power efficiency above 85 per cent compared to pulse-width modulation (PWM) buck controllers that drop as low as 30 per cent power efficiency at light load. This feature benefits applications that are in standby mode or operate at low current for a majority of the time.
The Hyperlight Load device also offers the HyperSpeed Control, a trademark circuitry that provides very fast transient response. The fast transient response minimises the output voltage ripple during any load changes, which allows customers to use very small output ceramic capacitors. Our modules offer exceptionally fast transient response, allowing our customers to use very small inexpensive ceramic capacitors and handle very fast current load changes without affecting the output voltage.
Q. What is pre-biased soft start?
A. Pre-biased soft start is an internal circuitry that reduces the input power supply surge current at start-up, which can cause a voltage drain on the input power supply. By initially slowing the output rise time, less surge current is required to charge the input capacitor. This circuitry is disabled after the soft start cycle ends to reduce current consumption.
Q. What is hiccup mode current limiting? How is it useful?
A. The modules offer a programmable short circuit limit that protects the DC/DC buck converter from a severe short circuit condition. The short circuit limit can be easily programmed by choosing the appropriate resistor value. When the programmed short circuit current is triggered, the device enters into a hiccup cycle to reduce the stress on the switching field-effect transistors (FETs) and to protect the load and supply from a severe short condition. This feature helps ensure that the DC/DC converter is protected from a catastrophic failure such as short on the output.
Q. How does under voltage lockout affect the working or efficiency of a device?
A. Our modules are designed to work in a wide input range. For example, the MIC28304 can operate from 4.5V to 70V input supplies. To ensure proper operation during power-sag conditions with very low input voltage, the modules have under-voltage lockout circuitry that disables the output when the supply voltage drops below a specified voltage such as 4.2V. This feature does not affect efficiency but assures that the device can operate within the scope of the design.
Q. What are the challenges involved in designing a better power module with the decreasing size of the devices? How can they be improved?
A. This is the real trick, as the size decreases the power devices need to be carefully chosen as not to affect the power efficiency. Typically, for a smaller device, power efficiency is compromised for size. At Micrel, we use very innovative and proprietary technology that allows us to assemble our devices in a smaller footprint without compromising power efficiency.
Q. How is the European Union’s EN 55022 standard different from the International Special Committee on Radio Interference’s CISPR 22 standard?
A. EN 55022 is a modified derivative of CISPR 22 and the European standard for information technology equipment (ITE). Procedures are given for the measurement of the levels of spurious signals generated by the ITE and limits are specified within the standard for protection of radio services in industrial, commercial or residential environments.
Q. How are the industry requirements changing with the changing standards of the power modules?
A. Today, modules are used in low volume applications or in time-critical designs, but are typically replaced by discrete solutions due to the higher cost of the modules. As the module gets closer to the cost of the discrete solution, modules will be used in high volumes applications. The big push will be on the price of the modules. At Micrel, we are ready to ramp up to volume demand, allowing for a more aggressive pricing strategy.
Q. What are the basic specifications that need to be taken care of while selecting a suitable power module for an application?
A. The customer needs to first identify what is the input voltage that they need to step down. What are the Point of Load (POL) requirements such as operating voltage and current requirements. The customer needs only to chose the appropriate module that matches the power needs. Micrel offers a family of products that serves almost all power rails from 5V up to 70V. The customer simply uses the resistor voltage divider to program the output voltage and chose the appropriate Input and Output capacitors to match up to the input and output voltages respectively; It’s that simple.
Sneha Ambastha is a technology journalist at EFY, Gurgaon.
