LTpowerCAD Quick Start Guide - Linear Technology

LTpowerCAD TM Design Tool 

Quick Start Guide 

Ver. 1.2.2.1 

Dec 2011 

Design Tool Development Team 

Power Products, Linear Technology 

Corp. 

LTpowerCAD@Linear.com 

Copyright © 2010 Linear Technology. All rights reserved

2 

LTpowerCAD 

TM Design Tool 

A Powerful Switching Regulator Design Tool for Selected 

LTC’s Monolithic and Module DC/DC Regulators. 

 

 

 

 

 

 

 

 

 

 

Step-by-Step Switching Regulator Design 

Friendly Graphical User Interface 

Simple LTC Product Selection Guide 

Power Component Design Wizard with Efficiency Estimation 

Control Feedback Loop Optimization with Accurate Bench Verified Small 

Signal Model 

Interface with LTspice TM Simulation 

Built-in Layout Examples 

Built-in Component Libraries 

Supports more than 150 Linear Tech Monolithic and Module Regulators 

Free Download at http://www.linear.com/designtools/software/ 

LTpowerCAD TM Design Tool Quick Start Guide Copyright © 2010 Linear Technology. All rights reserved

VIN 

Irms_max= 2.33 A Suggested L 0.58 µH 

MFR 

MFR 

Part # Part # Click on the inductor or capcitor symbols to link to the library. 

C 150 µF # of parallel parts 

1 L 0.6 µH 

Ripple RMS 10 A DCR 3.5 mΩ 

Check if they are phase interleaved 

# of Caps 1 i pp 38.69 % Vo 1.500 V @ 5A 

Max ipk 6.09 A Vopp 17.97 mVpp 

±V opp/V o 0.60 % 

Suggested Ron (1%) 

Actual Ron 

Actual fs at Vin_nom 

Off time at V in_min 

On time at V in_max 

100 kΩ 

1000.00 kHz 

783.75 ns 

161.29 ns 

Actual V von= 

1.50 V 

Output bulk caps selection: Output ceramic caps selection: 

MFR 

MFR 

Part # Part # 

C 100.00 µF C 10.00 µF 

Sug.R 2(1%) #NAME? kΩ ESR 35.00 mΩ ESR 5.00 mΩ 

Actual R2 15 kΩ ESL 3.00 nH ESL 1.20 nH 

# of caps 1 # of caps 1 

Actual R 1 

10 kΩ 

DC voltage and temperature degradation of capacitors 

1% res Resolution sel. are not considered, please enter actual capacitances. 

Please contact your local LTC sales office for technical supports. 

Voltage Divider Network Tuning 

Maximum phase boost of divider network= 

V out Expected phase boost of divider network at f c= 

R 2 

V fb 

R 1 

C1 

C 2 

Compensator Network Tuning 

ith 

C2 

C 1 

C th 

R th 

C thp 

I o 

Actual R 1= 

Actual R 2= 

Actual Vo set by R 1 and R 2= 

Calculated C 1= 

Calculated C 2= 

Calculated C th= 

Calculated R th= 

Calculated C thp= 

Actual voltage loop bandwidth, [f c_actual] actual]= 

#NAME? deg 

10.00 deg 

10 kΩ 

15 kΩ 

1.500 V 

#NAME? pF 

#NAME? pF 

0.00 pF 

0.00 pF 

Check if ITH pin is tied to INTVCC 

Actual voltage loop phase margin, [Φm_actual]= 

995.44 pF 

1.45 kΩ 

132.63 pF 

1000 pF 

2.40 kΩ 

220 pF 

10 V 

2 A 

76.20 kHz 

74.28 deg 

0 

-2 

-4 

-6 

-8 

Vout-to-Vfb 

-10 

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 

Frequency(Hz) 

Magnitude Phase 

80 

60 

40 

20 

0 

-20 

Voltage Loop Gain 

-40 

0 

1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 

Frequency(Hz) 

Frz_mag Mag Frz_phase Phase fc fsw/2 

f 

1 

0.8 

0.6 

0.4 

0.2 

180 

150 

120 

90 

60 

30 

3 



Step-by-Step Power Supply 

Design 

CIN selection: 

LTC3608 

Frequency resistor selection: 

#NAME? kΩ PV IN 

SW 

L 

± 

Vo 

R ON SV IN 

PGND 

C bulk 

C cer 

I ON SGND 

I TH 

V o 

C IN 

R 3 


V ON 

V FB 

R 

R 2 

4 

C TH 

3 

C THP 

(OPT) 

R TH R 1 

L selection: 

Export to LTspice 

View Layout Example 

C th 

R th 

C thp 

Magnitude(dB) 

Magnitude(dB) 

V in 

0 

Phase (degree) 


Input specs Part Selection Schematic/ 

Component 

Design 

Loop 

Compensation 

LTspice TM 

Simulation 


4 



Software Installation 


5 

Requirement 

The following system and software is required before 

installing LTpowerCAD 

TM 

 

Design Tool 

Personal Computer with Microsoft Windows XP SP2 or later OS 

Microsoft Office Excel 2000, 2003, 2007 or 2010 

 

Microsoft .NET Framework 3.5 or Higher 

Note: 

Windows Vista or Windows 7 based PC has .NET Framework integrated. 

Some Windows XP based PC may need additional installation of the .NET Framework, 

which can be free downloaded at www.microsoft.com. 

com 

Please refer to the appendix slides for details. 


6 

Download LTpowerCAD 


1. Go To Linear Tech Website “www.linear.com” 

Click “Design Support” 

Or Click Here to Download 

LTpowerCAD Design Tool 

Or Click Here to Download 


2. Click “Design Support” Hyperlink 


7 

Download LTpowerCAD TM Design Tool (2) 

3. Click “Download LTpowerCAD” Hyperlink to Start Downloading 



Click to Start Downloading 



8 

Install LTpowerCAD 


1. Double Click “Setup.exe” to Start LTpowerCAD TM Design Tool Setup Wizard 

2. Click “Next” Button 

3. Read the License Agreement, Select “I Agree” and Click “Next” Button 

4. Select the folder to install LTpowerCAD TM Design Tool and Click “Next” Button 

Select Install Folder 

Select “IA Agree” 

Click “Next” Click “Next” Click “Next” 


9 

Install LTpowerCAD TM Design Tool (2) 

5. Click “Next” Button 

6. Click “Close” Button to Finish Installation 

“LTpowerCAD” 

shortcut 

t 

Click “Next” 

Click “Close” 

7. Setup will automatic generate “LTpowerCAD” shortcut at 

Desktop and Start Menu 


10 

Getting Started With 



11 

Main Menu 


12 

Functions 

Start a New Design Project 

from Part Search Engine 

Open an Existing 

Design Project 

Help Documents 

Sync Release 

Function for New 

Models and 

Updates 

LTC Sales Contacts 


VIN 

MFR 

MFR 

# of parallel parts 


# of Caps 1 ipp 38.69 % Vo 1.500 V @ 5A 

Suggested Ron (1%) 

C2 

Actual Ron 

C1 

C2 

Cth 

Rth 

Cthp 

MFR 

±V opp/V o 0.60 % 

MFR 

Actual R 2 15 kΩ ESL 3.00 nH ESL 1.20 nH 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

-10 

0 

-2 

-4 

-6 

-8 

-10 

Please contact your local LTC sales office for technical supports. 

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 

80 

60 

40 

20 

0 

-20 

-40 

Magnitude 

Phase 

1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 

Frz_mag Mag Frz_phase Phase fc fsw/2 

-2 0 2 4 6 8 10 12 14 16 18 

0 

1 

0.8 

0.6 

0.4 

0.2 

180 

150 

120 

90 

60 

30 

13 

Design Procedure 

Main Menu 

Design Spreadsheet 

Enter Supply 

Specifications 

Design Power 

Stage 

Components 

CIN selection: 

L selection: 

Irms_max= 2.33 A Suggested L 0.58 µH 

Export to LTspice 


Part # Part # Click on the inductor or capcitor symbols to link to the library. 

C 150 µF C 1 L 0.6 µH 

IN 

Ripple RMS 10 A DCR 3.5 mΩ 

LTC3608 

Max i pk 6.09 A V opp 17.97 mV pp 

Frequency resistor selection: 

L 

± 

#NAME? kΩ PV IN 

SW 

Vo 

100 kΩ 

Actual f s at V in_nom 1000.00 kHz 

R 

Off time at V in_min 783.75 ns ON SV IN 

PGND 

Cbulk C cer 

On time at V in_max 161.29 ns 

I ON SGND 

Actual V von= 1.50 V V Output bulk caps selection: Output ceramic caps selection: 

ON I TH V FB 

V o R Part # Part # 

R 2 

4 C 100.00 µF C 10.00 µF 

C TH Sug.R2(1%) #NAME? kΩ ESR 35.00 mΩ ESR 5.00 mΩ 

R 3 C THP 

# of caps 1 # of caps 1 

(OPT) 

R TH R 1 Actual R 1 

10 kΩ 

DC voltage and temperature degradation of capacitors 

1% res Resolution sel. are not considered, please enter actual capacitances. 

Search & 

Select an LTC 

Part 

Design Control 

Compensation 

Loop 

Voltage Divider Network Tuning 

Vout-to-Vfb 

Maximum phase boost of divider network= #NAME? deg 

V out Expected phase boost of divider network at fc= 10.00 deg 

R Actual R1= 

10 kΩ 

2 

Actual R2= 

15 kΩ 

V fb 

Actual Vo set by R1 and R2= 1.500 V 

Calculated C1= #NAME? pF 

R 1 

C 1 

Calculated C 2= #NAME? pF 

0 

0.00 pF 

Frequency(Hz) 

0.00 pF 

Compensator Network Tuning 

Check if ITH pin is tied to INTVCC 

Voltage Loop Gain 

Calculated C th= 995.44 pF 

Calculated R th= 

1.45 kΩ 

ith 

Calculated Cthp= 132.63 pF 

1000 pF 

C th 

C 

2.40 kΩ 

thp 

220 pF 

R th 

V in 10 V 

I o 

2 A 

Actual voltage loop bandwidth, [fc_actual]= 76.20 kHz 

Frequency(Hz) 

Actual voltage loop phase margin, [Φm_actual]= 74.28 deg 

Magnitude(dB) 

Magnitude(dB) 



Interface with LTSpice 

Transient 

Response 

Estimation 

Load Transient Approximation (Second Order Approximation. Duty cycle and error amplifier 

saturation, subharmonic and switching delay not included, valid only with a stable system.) 

Load step= 

2.00 A 

Load step di/dt= 10.00 A/µsec 

Regulator 

di/dt 

I_step 

Vo(mV) 

Freeze current design 

Unfreeze 

Average Vout Overshoot/Undershoot Approximation during Load Transients 

0.2, 79.0 

Time(usec) 

Time Scale 

26 

LTSpice TM 

Simulation 

Layout Example 


14 

Start a New Design 

1. Double Click “LTpowerCAD” Shortcut on Windows Desktop or Start 

Menu to Start LTpowerCAD TM Design Tool 

Click to Start a New Design 

2. Click “Start New Design” Button 


Enter Supply Specification and Search 

LTC Part 

15 

3. Enter Design Specifications 

Enter Design Specifications 

Select Design Features 

Start to Search Suitable LTC Part 

Display All Supported Parts 

4. Click “Search” Button for the LTpowerCAD TM Design Tool Built-in Part 

Search Engine to Search for Suitable LTC Parts 

If Necessary, Click “All Parts” Button to Display All Supported LTC Parts 


Select LTC part --- If you already know 

the part# 

16 

5. Enter the LTC Partial Part Number to Refine and Narrow the Search 

Results 

Enter Partial Part Number 

to Refine the Search Results 


Search LTC Part --- Web Search (Optional) 

17 

If the LTpowerCAD TM 

Specification 

Design Tool Couldn’t Find the Part According to the 

Go To LTC Web 

LTC Web Search Engine 

1. Please Double Check Your 

Circuit Specifications 

2. Click “LTC Web Search” 

Button or “Go To LTC Web” 

Button to Search Among More 

Parts From Linear Technology 

Website 

3. Please Contact Your Local 

Sales Representative 

NOTE: Currently, the LTpowerCAD 

TM 

Design Tool Only Supports Limited Monolithic and 

uModule Parts. 

Please Visit www.linear.com or Call Your Local Sales Representative for More Information 


18 

Start Design 

6. Click “Start Design” Button to Save and Start a New Design 

Start Design 

Go To LTC Website 

7. Click “Web Link” Button to Open the Linear Tech Website for the 

Selected Part 


19 

Save Design File 

7. Before Starting a New Design, Select a Folder and Click “Save” 

Button to Save the New Design File 

Click “Save” Button 

8. User will be automatically directed to a Microsoft Excel Based Design 

Spreadsheet for the selected LTC Part 


Enable Macros to Use the Design 

Spreadsheet 

20 

User Needs to Enable Macros Feature in Microsoft Excel 2003 and 2007 

Microsoft Excel 2007 Microsoft Excel 2003 

Security Warning 

Enable this content 

Enable Macros 

• Click “Option…” Button 

• Select “Enable this content” 

t” 

• Click “Enable Macros” Button 


21 

Design Spreadsheet 

Control Loop Design Section 

Converter Spec. 

Section 

Power Component Design 

Section 

Load Transient Estimation 

Section 

Values in Yellow Boxes are Recommended by the Design Tool 

Values in Light Blue Boxes are Selected or Entered by the User 

Values in Red Fonts are Showing Warning Messages 


22 

Design and Optimize Power Components 

Power Component Design is Guided with a Schematic Based 

Interface 

Cin RMS Current 

Peak Inductor Current 

Output Ripple 

Vo Trim Resistor Value 

Click the Inductor or Capacitor 

Symbols to Link to the Build-in 

Component Library 


23 

Control Loop Compensation Design 

Design Control Loop By Simply Adjusting the Sliding 

Bar 

Sliding 

Bar 

Loop Bandwidth 

Gain Margin 

Loop Gain Prediction 

Output Impedance Prediction 


Export Design to LTspice TM 

(Optional) 

All Converter Design Parameters will 

Automatically be Exported to 

LTspice TM Simulator for Simulation 

Simulator 

24 

Free Download of LTspice TM at 

http://www.linear.com/designtools 

/software/ltspice.jsp 

/lt LTpowerCAD TM Design Tool Quick Start Guide Copyright © 2010 Linear Technology. All rights reserved

25 



26 

Summary of Design 

Click “Summary” Sheet to Review the Design Summary 

Power 

Component 

Summary 

Stress 

Analysis 


27 

Open an Existing Design 

1. Click “Open Existing Design” Button on the Main Menu 

Open an Existing Design 

2. Select the Design File and Click “Open” Button 


28 



Support 


29 

Help Document 

Click “Help” Button on the Main Menu 

Help 

A Separate PDF Help File is also Available on Linear Tech Website for Review 


30 

Sync Release 

Click “Sync Release” Button on the Main 

Menu 

Sync Release 

NOTE: 

The computer needs to have an internet connection before using the “Sync Release” function. 


31 

Technical Support 

Please Contact Us at LTpowerCAD@linear.com for Any 

Questions and Suggestions Regarding the 


Thank You For Using Linear Technology 




32 



Appendix 


33 

Download Microsoft .NET Framework 

1. Go To Microsoft Website “www.microsoft.com” 

Click “.NET Framework” 

2. Click “All Products” and “.NET Framework” Hyperlink 

Click “.NET Framework 3.5 SP1” 


34 

Download Microsoft .NET Framework (2) 

3. Click “Install it now” Button 

Click “Install it now” 

4. Click “Download” Button to Start Downloading .NET Framework 3.5 

Click to Start t Downloading 

.NET Framework 3.5

LTpowerCAD Quick Start Guide - Linear Technology

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