Part # Application Note Power Supply And Power Management L4973 AN1126 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: Current sharing of the L4973 in a multiphase application

Part Details:

AN1126 ® APPLICATION NOTE CURRENT SHARING OF THE L4973 IN A MULTIPHASE APPLICATION by Domenico Arrigo & Giuseppe Gattavari INTRODUCTION 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, andthe output ranges from 3.3V (L4973D3.3) and 5.1V(L4973D5.1) to 40V. Other regulated outputs below3.3V 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 7Athe efficiency is 87%. At 3.5A output, the efficiency is 90%. Electrical Specifications Input Voltage range 8V-30V Output Voltage 5.1V ±3% (Line, Load and Temperature) Output Voltage Ripple 47mV (0.92%/Vo) Output Current range 0 to 7A Max Output Ripple current 15% Min Iomax Current limit 8A Switching frequency 200kHz Current Sharing Operating PrincipleThe current sharing configuration, shown in fig. 1, is based upon two L497x devices U1 and U2. Any de-vice in the L497x family can be used for this purpose.The U1 regulator acts as a master which regulates the output voltage. The second section U2 works as a current follower. Its task is to deliver an output current equal to the Figure 1. Current Sharing Operating Principle FB I - L Vcc OUT U1 Rs L497x COMP Cint Rint Vcc GND Vout - + OP-AMP FB I + Cout L Vcc OUT U2 Rs COMP L497x GND May 1999 1/16

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Application Note Power Supply And Power Management L4973 AN1126.pdf Datasheet