National Semi Introduces Small Step-Down Switching Regulators For Handheld Devices & Automotive Power Adapters
National Semiconductor Corp. announced two new step-down switching regulators well-suited for handheld devices and automotive power adapters. The highly integrated LM34917A and LM34919, members of National’s PowerWise® energy-efficient product family, are described as the industry’s smallest non-synchronous buck regulators to feature a supply voltage rating up to 50V, 1.25A continuous output current, intelligent current limiting and over-voltage protection.
National’s new LM34917A and LM34919 feature programmable switching frequency up to 2 MHz. The products integrate MOSFET switches to reduce system component count, and a high switching frequency is said to enable use of ultra-small inductors and capacitors for very small solution size.
The LM34917A and LM34919 utilize a constant on-time (COT) control scheme, which requires no loop compensation. The regulators are well-suited for use in applications that require high-input voltage regulations such as MP3 players utilizing Firewire connectivity (IEEE1394) as well as MP3 players or auxiliary power adapters with direct connection to a 12V (universal) automotive power outlet where transient protection requirements can exceed 40V.
The LM34917A and LM34919 feature peak efficiency equal to or greater than 90%, positioning it among National’s PowerWise® family of energy-efficient products. The products feature ultra-small micro SMD packaging and extend National’s buck regulator product line which includes the LM2694, LM34910 and LM34914 buck regulators offered in LLP® packaging. The LM34917A and LM34919 step-down switching regulators feature all of the functions needed to implement a low-cost, efficient buck bias regulator.
The LM34917A buck regulator supplies up to 1.25A to the load. It contains an N-Channel MOSFET buck switch and is available in a 12-pin. 2 x 2.3mm micro SMD package. In addition to no loop compensation, the COT feedback regulation scheme is also said to result in fast load transient response and simplified circuit implementation. The operating frequency remains constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The valley current limit results in a smooth transition from constant voltage to constant-current mode without foldback when the output is overloaded. Additional features include VCC under-voltage lockout, thermal shutdown, gate drive under-voltage lockout and maximum duty cycle limiter.
The LM34919 buck regulator supplies up to 0.6A to the load and features the constant on-time feedback regulation scheme of the LM34917A. The LM34919 is offered in a 10-pin, 1.5 mm x 2mm micro SMD package.
Available now, the LM34917A is priced at $1.35 each and the LM34919 is priced at $1.05 each. All prices are in 1,000-unit quantities.
