National Semiconductor has introduced what the company claims is the industry's first full-bridge pulse width modulation (PWM) controllers to integrate all four primary-side bridge MOSFET gate drivers. The LM5045 and LM5046 are well-suited for delivering higher efficiency and higher power density in quarter-brick and eighth-brick power modules used in a variety of high input voltage communications infrastructure applications.
The new LM5045 and LM5046 PWM controllers ease the design of full-bridge topology-based power converters into small-form-factor power supplies by reducing the number of external power components needed with existing full-bridge solutions. The LM5045 contains all of the features necessary to implement a conventional full-bridge topology power converter using either current mode or voltage mode control. For applications requiring zero-voltage switching to minimize electro-magnetic interference (EMI) due to switching noise, the LM5046 contains all the features necessary to implement a phase-shifted full-bridge topology.
Offered in small, thermally enhanced 5.0mm by 5.0mm by 0.8mm LLP and 4.4mm by 9.7mm by 0.9mm TSSOP packages, the full-bridge controllers operate on the primary side of an isolated DC-DC converter with input voltage up to 100V. These highly-integrated controllers provide robust 2A high and low side gate drivers for the four external bridge MOSFETs in addition to the control signals for the secondary side synchronous rectifier MOSFETs and an internal high voltage start-up regulator. Intelligent startup of the synchronous rectifiers (SR) allows monotonic turn-on of the power converter, even with pre-bias load conditions. The synchronous rectifier control signals offer independent and programmable leading/trailing edge dead-times between the primary and secondary MOSFET control signals for optimizing efficiency, and the SR signals are limited to 5V for use with digital isolators. Additional features include dual mode over-current protection featuring both cycle-by-cycle current limiting and hiccup mode restart, programmable soft-start, timing for both primary and synchronous rectifiers, programmable line UVLO and OVP, a synchronizable 2MHz oscillator and thermal shutdown.
National's new LM5045 and LM5046, together with secondary side FET drivers such as the LM5110, LM5111 and LM5112, provide a complete controller solution to implement a highly efficient, small form factor full-bridge power converter.
National's new full-bridge PWM controllers are available now and offered in 28-pin LLP and thermally-enhanced TSSOP packages. Priced in quantities of 1,000, the LM5045 is US$2.25 and the LM5046 is US$2.45.