Datasheet LTC7804 (Analog Devices) - 28
| Fabricante | Analog Devices |
| Descripción | Low IQ Synchronous Boost Controller |
| Páginas / Página | 34 / 28 — APPLICATIONS INFORMATION. TYPICAL APPLICATIONS. Figure 7. Recommended … |
| Formato / tamaño de archivo | PDF / 1.5 Mb |
| Idioma del documento | Inglés |
APPLICATIONS INFORMATION. TYPICAL APPLICATIONS. Figure 7. Recommended Printed Circuit Layout Diagram
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Versión de texto del documento
LTC7804
APPLICATIONS INFORMATION
the sensitive current and voltage sensing traces. In addition, The output voltage under this improper hookup will still investigate common ground path voltage pickup between be maintained but the advantages of current mode control these components and the GND pin of the IC. will not be realized. Compensation of the voltage loop An embarrassing problem, which can be missed in an will be much more sensitive to component selection. This otherwise properly working switching regulator, results behavior can be investigated by temporarily shorting out when the current sensing leads are hooked up backwards. the current sensing resistor—don’t worry, the regulator will still maintain control of the output voltage.
TYPICAL APPLICATIONS
SENSE– RUN VIN SENSE+ SW L1 RSENSE LTC7804 TG C PLLIN/SPREAD B FREQ BOOST M1 + fIN MODE BG M2 RUN VFB VBIAS + GND VIN ITH GND INTVCC SS VOUT 7804 F07
Figure 7. Recommended Printed Circuit Layout Diagram
L1 V R SW IN SENSE VOUT RIN C C OUT RL IN 7804 F08 BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH
Figure 8. Branch Current Waveforms
Rev. 0 28 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Main Control Loop INTVCC/EXTVCC Power Boost Supply and Dropout (BOOST and SW Pins) Shutdown and Start-Up (RUN, SS Pins) Light Load Current Operation: Burst Mode Operation, Pulse-Skipping or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum and Phase-Locked-Loop (FREQ and PLLIN/SPREAD Pins) Operation When VIN > VOUT Operation at Low Input Voltage BOOST Supply Refresh and Internal Charge Pump Applications Information SENSE+ and SENSE– Pins Low Value Resistor Current Sensing Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Power MOSFET Selection CIN and COUT Selection Setting Output Voltage RUN Pin Soft-Start (SS Pin) INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Phase-Locked Loop and Frequency Synchronization Setting the Operating Frequency Selecting the Light-Load Operating Mode Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Efficiency Considerations Checking Transient Response Design Example PC Board Layout Checklist PC Board Layout Debugging Package Description Typical Application Related Parts
APPLICATIONS INFORMATION
the sensitive current and voltage sensing traces. In addition, The output voltage under this improper hookup will still investigate common ground path voltage pickup between be maintained but the advantages of current mode control these components and the GND pin of the IC. will not be realized. Compensation of the voltage loop An embarrassing problem, which can be missed in an will be much more sensitive to component selection. This otherwise properly working switching regulator, results behavior can be investigated by temporarily shorting out when the current sensing leads are hooked up backwards. the current sensing resistor—don’t worry, the regulator will still maintain control of the output voltage.
TYPICAL APPLICATIONS
SENSE– RUN VIN SENSE+ SW L1 RSENSE LTC7804 TG C PLLIN/SPREAD B FREQ BOOST M1 + fIN MODE BG M2 RUN VFB VBIAS + GND VIN ITH GND INTVCC SS VOUT 7804 F07
Figure 7. Recommended Printed Circuit Layout Diagram
L1 V R SW IN SENSE VOUT RIN C C OUT RL IN 7804 F08 BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH
Figure 8. Branch Current Waveforms
Rev. 0 28 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Main Control Loop INTVCC/EXTVCC Power Boost Supply and Dropout (BOOST and SW Pins) Shutdown and Start-Up (RUN, SS Pins) Light Load Current Operation: Burst Mode Operation, Pulse-Skipping or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum and Phase-Locked-Loop (FREQ and PLLIN/SPREAD Pins) Operation When VIN > VOUT Operation at Low Input Voltage BOOST Supply Refresh and Internal Charge Pump Applications Information SENSE+ and SENSE– Pins Low Value Resistor Current Sensing Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Power MOSFET Selection CIN and COUT Selection Setting Output Voltage RUN Pin Soft-Start (SS Pin) INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Phase-Locked Loop and Frequency Synchronization Setting the Operating Frequency Selecting the Light-Load Operating Mode Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Efficiency Considerations Checking Transient Response Design Example PC Board Layout Checklist PC Board Layout Debugging Package Description Typical Application Related Parts