LM2698 Reference Design - 8x4 LED array, with PWM dimming

Design Specifications

Inputs	Outputs #1
VinMin=5.0	Vout1=16
VinMax=5.0	Iout1=0.160

Design Resources

LM2698 Reference Design

Additional Resources

•	LM2698 Product Folder
•	LM2698EVAL Evaluation Board

Bill Of Materials

Part	Manufacturer	Part#	Attributes
Cc	Vishay	VJ0805Y472KXXAT	4.7n F
Cin	TDK	C3216X7R1A106M	NumCaps=1, 10u F
Co	TDK	C3216X7R1E106M	10u F
D1	Vishay	SS12	0.5 V
L1	TDK	SLF7032T-330MR75-2	33u H, 0.016 Ohms
Q1	Vishay	2N3906
Q2	Vishay	2N3906
Q3	Vishay	2N3906
Q4	Vishay	2N3906
Q5	Vishay	2N3906
Q6	Vishay	2N3906
Q7	Vishay	2N3906
Q8	Vishay	2N3906
R1	Vishay	CRCW080561R9F	61.9 Ohms
R2	Vishay	CRCW080561R9F	61.9 Ohms
R3	Vishay	CRCW080561R9F	61.9 Ohms
R4	Vishay	CRCW080561R9F	61.9 Ohms
R5	Vishay	CRCW080561R9F	61.9 Ohms
R6	Vishay	CRCW080561R9F	61.9 Ohms
R7	Vishay	CRCW080561R9F	61.9 Ohms
R8	Vishay	CRCW080561R9F	61.9 Ohms
Rc	Vishay	CRCW08052494F	24.9k Ohms
U1	National Semiconductor	LM2698

Design Description

This circuit consists of a power section optimized to deliver a total of 160mA to the LED array. The first string is controlled by the feedback loop to 20mA. The remaining strings are controlled by the current mirrors created by the PNP transistors at the top of each string.

Schematic

The WEBENCH® Electrical Simulator requires the Adobe Flash Player minimum version of 8,0,0,0.

A new browser window has been launched (a pop-up) to install the Flash player.
Please disable the appropriate browser pop-up blockers.

It appears that your web browser does not have any Flash plugin or at least not the required version.
We recommend that you close all browser windows (except this one, of course) before continuing.

After the correct version of Flash has been installed please refresh this page and proceed to use the WEBENCH Electrical Simulator.

Refresh this page
The installation/upgrade process will probably only require that you refresh this page. However, depending on your web browser, this upgrade might require closing and re-opening your web browser. It might even require that you reboot your system.

A separate installation window has been opened for you. If for some reason it does not appear, you can click here or the latest version of the Flash plugin for your browser can be downloaded from
Get Flash.

If you are still having trouble with the upgrade you can try the following;

Bookmark this page

Uninstall Flash using uninstaller from this page.

Close all web browser windows

Restart the web browser and return to this page.

Click here to test the version of Flash that is currently running on your system.

Adobe web site.

Example Schematic Showing Connection for all Components.