1/15/2003 - Texas Instruments (TI) introduced two new synchronous buck drivers for high-efficiency, non-isolated, low output voltage DC/DC converters. Providing system power designers up to four percent more efficiency and up to 40 percent improved heat dissipation, each driver can be used with 12V or 5V input systems, or with 3.3V input systems with higher bias rail, to generate lower output voltages for central processing units (CPU), general computer, data communications, telecommunications and general merchant power supply applications.
"Typical gate drivers with adaptive delay techniques wait for one switch to be turned off before turning on the other to prevent cross-conduction, which always results in an inherent dead-time where body diode conduction losses occur," said John Vigars, product line manager for TI's power supply control products. "With today's low output voltages and higher operating frequencies requirements, these body-diode losses become increasingly significant. These new drivers quickly find the optimal overlap between both gate drive transitions to eliminate the body-diode conduction and adjust for temperature variations and load-dependent delays."
The UCC27221 and UCC27222 drivers, which produce ±3A of output drive current for efficient power MOSFET switching at the critical Miller plateau region, employ TI´s Predictive Gate DriveTM control technology to reduce diode conduction and reverse recovery losses in the synchronous rectifier metal-oxide semiconductor field-effect transistors (MOSFET(s)). This proven technology employs a closed loop feedback system that detects body-diode conduction, and adjusts dead time delays in the next switching cycle to minimize the conduction time interval in synchronous rectifiers.
Both drivers incorporate TI´s hybrid TrueDriveTM output stage with paralleled bipolar and complementary metal-oxide semiconductor (CMOS) transistors to allow efficient current delivery at low supply voltages. The UCC27221 has an inverted pulse-width modulation (PWM) input while the UCC27222 has a non-inverting PWM input. Latch up and electrostatic discharge protection circuitries are also included.
UCC27221 and UCC27222 are available in volume from TI and its authorized distributors in a thermally enhanced low profile HTSSOP-14 PowerPADTM (PWP) package. Suggested resale pricing in quantities of 1,000 units is $1.25. Evaluation modules are currently available at power.ti.com.
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