Switching regulator provides up to 10A from a 3V to 75V input
04 June 2008
An emulated current mode controlled buck-boost DC-DC regulator controller has been launched by National Semiconductor.
With a voltage range of 3V to 75V, the LM5118 is claimed to be suited to automotive, telecommunications and battery-powered systems.
It features programmable switching frequency up to 500kHz, ultra-low shutdown current, and a smooth transition between buck and buck-boost modes. The LM5118 switching regulator features peak efficiency of 95 per cent, positioning it among the company's PowerWise family of energy-efficient products.
The two-switch configuration enables design engineers to assemble a complete power converter with ultra-wide input voltage range. Operation below 3V to 75V makes the LM5118 suitable for automotive applications such as powering the dashboard display, or electronic controls such as anti-lock braking or fuel injection control. These systems operate from a 12.6V battery, but with a weak battery during cold crank conditions, the voltage could momentarily fall down to 4V. To ensure control from electronic modules, the system must still operate at or below this voltage. The buck-boost control of the LM5118 makes this possible.
The regulator controller operates as a buck regulator when the input voltage is sufficiently greater than the regulated output voltage and gradually transitions to the buck-boost mode as the input voltage approaches the output. This dual-mode approach maintains regulation over a wide range of input voltages with optimal conversion efficiency in the buck mode and a glitch-free output during mode transitions. The LM5118 includes drivers for the high-side buck MOSFET and the low-side boost MOSFET. The emulated current-mode control reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of very small duty cycles necessary in high-input voltage applications. Additional protection features include current limit, thermal shutdown and an enable input.
The LM5118 is offered in a 20-pin thermally enhanced TSSOP package.
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