LM2737 Reference Design - 1 High Brightness LED, 2000 mA (Solar Cell)

Design Specifications

Inputs	Outputs #1
VinMin=12	Vout1=3
VinMax=14	Iout1=2.0

Design Resources

LM2737 Reference Design

Additional Resources

•	LM2737 Product Folder

Bill Of Materials

Part	Manufacturer	Part#	Attributes
A2	National Semiconductor	LMV321
Cb	Vishay	VJ1206Y104KXXAT	100n F
Cc1	Vishay	VJ1206A181KXX	180p F
Cc2	Vishay	VJ1206Y472KXX	4.7n F
Cc3	Vishay	VJ1206A681KXX	680p F
Cf1	TDK	C3216X7R1E105K	1u F
Cf2	Vishay	VJ1206Y104KXXAT	100n F
Cin	TDK	C3225X5R1C106	NumCaps=1, 10u F
Co	TDK	C3216X7R1A106M	10u F
Css	Vishay	VJ1206Y102KXX	1n F
D1	Vishay	MBR0520	0.3 V
L1	COILCRAFT	DO1813P-472HC	4.7u H, 0.054 Ohms
M1	Vishay	FDC6401N
Rc1	Vishay	CRCW12062211F	2.21k Ohms
Rf	Vishay	CRCW12061002F	10k Ohms
Rfrq	Vishay	CRCW12063012F	30.1k Ohms
Ri	Vishay	CRCW12064991F	4.99k Ohms
Rlm	Vishay	CRCW12064221F	4.22k Ohms
Rset	Vishay	CRCW1206R10J	0.1 Ohms
U1	National Semiconductor	LM2737
U3	National Semiconductor	LM78L05

Design Description

This circuit delivers a constant current of 2A to a multi-die IR LED device. The solar cell input requires very high efficiency, and a synchronous buck controller allows the use of a small FET at high frequency (800kHz) to achieve that efficiency. The LM78L05 provides a simple 5V rail for both the logic and FET drive of the LM2737 and the LMV321.

The LM2737 is especially well suited to PWM because the LM2737 discharges the output through the bottom power FET when disabled.

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.