LM5007 Reference Design - Buck Bias Converter: 18-42V Input, 13V @ 70 mA Output

  Design Specifications

Inputs Outputs #1
VinMin=18 Vout1=13
VinMax=42 Iout1=0.07
   Design Resources

LM5007 Reference Design

  Additional Resources


LM5007 Product Folder
LM5007EVAL Evaluation Board
LM5007SD-EVAL Evaluation Board
   Bill Of Materials

Part Manufacturer Part# Attributes
C1 TDK C3216X7R1H474 470n F
C2 TDK C3216X7R1H474 470n F
C3 Vishay VJ0805Y104KXXA 0.1u F
C4 Vishay VJ0805Y104KXXA 0.1u F
C5 Vishay VJ0805Y104KXXA 0.1u F
C6 TDK C3216X7R1H474 10u F
C7 TDK C3216X7R1C106 470p F
C8 NOT INSERTED NOT INSERTED
C9 NOT INSERTED NOT INSERTED
D1 Diodes Inc B1100 0.79 V
D2 ONSEMI BAT54H 0.32 V
L1 Pulse P1167-474 353u H, 1688m Ohms
R1 Vishay CRCW08051403F 140k Ohms
R2 Vishay CRCW08051R00F 1 Ohms
R3 Vishay CRCW08051003F 100k Ohms
R4 Vishay CRCW08058451F 8.45k Ohms
R5 Vishay CRCW08052001F 2k Ohms
R6 Vishay CRCW08050000F 0 Ohms
U1 National Semiconductor LM5007

  Design Description

This design employs the LM5007 step-down switching regulator. The LM5007 features all of the functions needed to implement low cost, efficient, Buck bias regulators. This high voltage regulator contains an 80 V, 0.7A N-Channel Buck Switch. The device is easy to apply and is provided in the MSOP-8 and the thermally enhanced LLP-8 packages. The regulator is based on a hysteretic control scheme using an on time inversely proportional to VIN. This feature allows the operating frequency to remain

relatively constant with load and input voltage variations. The hysteretic control requires no control loop compensation, while providing very fast load transient response. An intelligent current limit is implemented in the LM5007 with forced off time that is inversely proportional to VOUT. This current limiting scheme reduces load current foldback. Additional protection features include: Thermal Shutdown, Vcc undervoltage lockout, gate drive undervoltage lockout, and Max Duty Cycle limiter.



  Schematic

Example Schematic Showing Connection for all Components.


  Layout


Board's Bottom View


Board's Top View


  Waveforms


Output Voltage Ripple

Start Up

Switch Pin

Transient Response