Power management chipset optimises dead time

26th May 2015

Barney Scott

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Texas Instruments has introduced the first PMIC chipset with intelligent digital control and a unique body-diode sensing feature to optimise secondary-side synchronous rectification in next-gen AC/DC and isolated DC/DC power supplies. The UCD3138A digital controller and UCD7138 low-side gate driver improve system efficiency and halve synchronous rectification MOSFET voltage stress compared to other digital-power solutions.

Accurate control of dead time in the synchronous rectifiers helps minimise power losses and reduces the risk of MOSFET failure. The UCD3138A and UCD7138 chipset use body-diode voltage information in fast digital control algorithms to dynamically optimise dead-time and compensate for power-stage component variations without calibration or screening during mass production. This helps telecomms and server end-equipment manufacturers more easily bring to market energy-efficient 80 PLUS Titanium-grade power supplies, which saves energy costs to information technology service providers.

Adjusting timing for minimal diode conduction increases efficiency and reliability, while eliminating the SNR challenges of traditional MOSFET VDS ON sensing devices. The UCD7138’s asymmetrical, rail-to-rail 4A source and 6A sink peak-current drive supports load range of a few hundred watts to 1kW where multiple paralleled FETs are used.

A 3x3mm QFN package reduces board space as well as parasitic inductances when placed alongside the synchronous rectifier MOSFETs. The hardware peripherals in the UCD3138A, along with 14ns propagation delays and fast rise/fall times with minimised tolerances in the UCD7138, enable extremely high frequencies up to 2MHz.

Along with this chipset, TI has also recently released a solution for lower-power AC/DC flyback converters. TI’s UCC24630 synchronous rectifier controller delivers the highest efficiency with low sensitivity to board layout and MOSFET package parasitics. Auto low-power detection and 110μA standby current also allow designers to easily achieve ultra-low standby power consumption.

Designers can quickly develop and debug applications with TI’s Code Composer Studio (CCS) IDE or refer to the TI Designs 340W digital controlled LLC resonant half-bridge DC/DC power conversion reference design.

The UCD3138A and UCD7138 devices are available now in the TI store and through the company’s authorised distribution network. The UCD7138 MOSFET driver is packaged in a 6-pin QFN package and is priced at $1.10 in 1,000-unit quantities. The UCD3138A digital controller is packaged in a 40-pin QFN package and is priced at $3.22 in 1,000-unit quantities.