The L4973 family is a 3.5A monolithic step-down dc-dc converter, available in POWERDIP18( 12+3+3) and SO20L (12+4+4) plastic packages. The operating input supply voltage range is from 8V to 55V, and the output ranges from 3.3V (L4973D3.3) and 5.1V(L4973D5.1) to 40V. Other regulated outputs below 3.3V are also possible (See Application Note AN938). Using two L4973D is possible to deliver up to 7A with a good sharing between the two sections or a re- dundant 3.5A. The two devices work at a switching frequency of 200kHz. At Vcc = 24V, Vo = 5.1V at 7A the efficiency is 87%. At 3.5A output, the efficiency is 90%.
The document details how to configure two L4973 devices in a multiphase application for current sharing. It explains the operating principle where one device acts as a master regulator and the other follows its output current, utilizing an op-amp to compare voltage drops across sensing resistors.
The text analyzes the benefits of introducing a phase delay between the two PWM signals compared to synchronized operation. It provides mathematical formulas and graphical data demonstrating how multiphase configurations minimize RMS current through input capacitors, reduce ripple, and improve overall efficiency under various duty cycles.
| Input Voltage range | 8V-30V |
|---|---|
| Output Voltage | 5.1V +3% |
| Switching frequency | 200kHz |
| Output Current range | Oto 7A |
Using two L4973D devices, it is possible to deliver up to 7A with good sharing between the two sections.
Multiphase application reduces the RMS current through the input capacitor, which minimizes wasted power and heat dissipation.