Product category:
Power Supply ICs and Controllers
News Release from: National Semiconductor | Subject: LM201xx and LM202xx synchronous buck regulators
Edited by the Electronicstalk Editorial
Team on 06 November 2007
Buck regulators enhance system
reliability
Synchronous buck regulators provide high-efficiency DC/DC power conversion for point-of-load power supply designs in applications such as communication, data storage, industrial and automotive.
The latest buck switching regulators from National Semiconductor combine self-synchronisation with high power density These 10 full-featured, synchronous buck regulators provide high-efficiency DC/DC power conversion for point-of-load power supply designs in applications such as communication, data storage, industrial and automotive
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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Part of National's PowerWise energy-efficient product family, the highly integrated regulators feature a variety of input voltages and output currents, and offer a combination of power sequencing, adjustable switching frequency and clock synchronisation options.
The new line of LM201xx and LM202xx synchronous buck regulators includes 2, 3, 4 and 5A output devices.
Each regulator integrates two switching MOSFETs and uses an externally compensated peak current-mode control loop, providing superior load transient response in low duty cycle applications.
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The external compensation allows the performance to be optimised for the output capacitor and inductor.
With current-mode control, just two external components are needed for compensation.
The ability of the 3 and 4A clock synchronisation devices to self-synchronise when in out-of-phase operation reduces input capacitance and voltage ripple in power supply designs.
National offers a downloadable power supply design tool for the new low voltage synchronous buck regulators that eliminates the need for tedious hand calculations.
The tool, in a Microsoft Excel spreadsheet format, calculates component values based on user-specified design parameters to quickly create a complete power supply design.
The design tool allows the design engineer to quickly analyse the control loop response, thermal performance and efficiency of the design.
Offered in a 16-pin thermally enhanced TSSOP package, the nine low-voltage buck regulators operate with an input voltage range from 2.95 to 5.5V and deliver up to 5A of continuous output current.
Both fixed and adjustable switching frequency versions are available.
Each buck regulator has a precise internal voltage of 1.5% accuracy from -40 to +125C while providing excellent line and load regulation.
They include a precision enable pin that allows accurate setting of the turn-on threshold and sequencing of the turn-on of multiple devices, eliminating the need for an external voltage supervisor chip.
Also included is a power good indicator that regulates the output voltage within tolerance and can sequence loads that have an enable input.
A tracking and soft-start feature allows the design engineer to set the output to accurately track an external supply, as well as provide a controlled voltage ramp to protect loads against in-rush current that could cause latchup.
The monotonic startup into prebiased load feature prevents the possibility of latchup in FPGA and ASIC applications.
The buck regulators enhance system reliability by using an accurate current limit to provide robust protection for long-term hard shorts while minimising the inductor size.
Overvoltage and undervoltage events are monitored at the output.
The low-voltage LM20123, LM20124 and LM20125 buck regulators feature fixed frequencies of 1.5MHz at 3A, 1MHz at 4A or 500kHz at 5A for enabling the smallest solution sise.
The low-voltage LM20143, LM20144 and LM20145 buck regulators feature adjustable frequencies for maximum design flexibility.
The low-voltage LM20133 and LM20134 buck regulators provide clock synchronisation for synchronisation to an external clock source.
The low-voltage LM20154 buck regulator features out-of-phase clock output for current sharing or out-of-phase operation.
The high-voltage LM20242 buck regulator, offered in a 20-pin TSSOP package with exposed pad, operates with an input voltage range from 4.5 to 36V and delivers up to 2A of continuous output current.
The LM20242 features adjustable frequency from 250kHz to 1MHz for maximum design flexibility.
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