ST 公司的L5973D是降壓單片開關功率穩壓器,開關電流大于2.5A,可向負載提供2A直流電流,輸入電壓從4V到36V,輸出電壓可設定為1.235V到35V,基準電壓3.3 V / (±2%),LDO工作,100%占空比,內部固定頻率250kHz,零負載電流工作和熱關斷特性,主要用在消費類電子如STB, DVD,TV, VCR,汽車收音機,LCD監視器,網絡設備如常XDSL,調制解調器,DC/DC模塊,計算機如打印機,音頻/圖像卡,光存儲,硬盤驅動,以及工業如汽車電池,EC/EC轉換器等.本文介紹了L5973D主要特性, 測試應用電路, 演示板電路和所用元件列表以及多種典型應用與MR-16格式HBLED驅動器的特性和詳細電路圖.

The L5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.5 A so it is able to deliver more than 2 A DC current to the load depending on the application conditions.

The output voltage can be set from 1.235 V to 35 V. The high current level is also achieved thanks to an SO8 package with exposed frame, that allows to reduce the Rth(j-amb) down to approximately 40℃/W.

The device uses an internal P-channel D-MOS transistor (with a typical Rdson of 250 mΩ) as switching element to minimize the size of the external components.

An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4 V only, it is particularly suitable for 5 V bus, available in all computer related applications.

Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.

L5973D主要特性:

■ 2.5 A internal switch

■ Operating input voltage from 4 V to 36 V

■ 3.3 V / (±2%) reference voltage

■ Output voltage adjustable from 1.235 V to 35 V

■ Low dropout operation: 100 % duty cycle

■ 250 kHz internally fixed frequency

■ Voltage feedforward

■ Zero load current operation

■ Internal current limiting

■ Inhibit for zero current consumption

■ Synchronization

■ Protection against feedback disconnection

■ Thermal shutdown

L5973D應用:

■ Consumer: STB, DVD, TV, VCR, car radio, LCD monitors

■ Networking: XDSL, modems, DC-DC modules

■ Computer: printers, audio/graphic cards, optical storage, hard disk drive

■ Industrial: changers, car battery, DC-DC converters


圖1.L5973D測試應用電路

圖2.L5973D演示板應用電路

演示板應用電路元件列表:



圖3.L5973D正向升壓/降壓穩壓器

圖4.L5973D升壓/降壓穩壓器

圖5.L5973D帶輔助繞組的雙輸出電壓穩壓器

STEVAL-ILL007V1: High intensity LED driver for MR-16 format based on L5973D
This reference design is a constant current driver for high brightness LEDs. The supply input voltage can be either 12 V AC or DC, and for DC it can range from 6 V to 24 V. It can also be adapted for reverse battery protection in automotive applications. The output is a constant current that can drive a single or multiple LEDs in series at 350 mA, 700 mA or 1.05 A.

STEVAL-ILL007V1 HBLED驅動器特性:

■ This evaluation board was designed so that it can be configured to accept several different input voltages

■ The most common input voltages are 12 Vac, 12 Vdc (for automotive) and 24 Vdc

■ The board also allows the user to select the output current by using jumpers setting only

■ The standard configuration of the board includes a full wave bridge rectifier that is
required for an AC input


圖6.STEVAL-ILL007V1 HBLED驅動器外形圖

圖7.STEVAL-ILL007V1 HBLED驅動器電路圖

詳情請見:
http://www.st.com/stonline/products/literature/ds/8588/l5973d.pdf
和
http://www.st.com/stonline/products/literature/bd/14175/steval-ill007v1.pdf