LM2794 - Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control
Datasheet Packaging Samples & Pricing Eval. Boards Reliability Application Notes Knowledge Base

Features
•Regulated current sources with ±0.5% matching between any two outputs
•High efficiency 3/2 boost function
•Drives one, two, three or four white LEDs
•2.7V to 5.5V Input Voltage
•Up to 80mA output current
•Analog brightness control
•Active-low or high shutdown input ('94/95)
•Very small solution size and no inductor
•2.3µA (typ.) shutdown current
•325kHz switching frequency (min.)
•Constant Frequency generates predictable noise spectrum
•Standard Micro SMD-14 package: 2.08mm X 2.403mm X 0.845mm High
•Thin Micro SMD-14 package: 2.08mm X 2.403mm X 0.600mm High

General Description

The LM2794/95 is a fractional CMOS charge-pump that provides four regulated current sources. More...


Applications

•White LED Display Backlights
•White LED Keypad Backlights
•1-Cell Li-Ion battery-operated equipment including PDAs, hand-held PCs, cellular phones
  Typical Application
click for larger image


ParametersValues
Regulated LEDs 4
Total LED Current 80 mA
Current Matching 0.5%
Boost Type Switched Capacitor 1.5x
Switching Frequency 515 kHz
Efficiency (peak) 80 %
Input Min Voltage 2.7 Volt
Input Max Voltage 5.5 Volt
Boost Voltage Unregulated
LED Configuration Parallel
Supply Current 5.5 mA
Switching Type Fixed Freq
Special Features Active low shutdown
PWM BrightCtrl Yes
Analog-V BrightCtrl Yes
Ambient Light Compensation No
RGB-LED No
Temperature Min -30 deg C
Temperature Max 85 deg C
RegType WhiteLED Driver
PowerWise No


Typical Performance

click for larger image


  Also Recommended
LM2796▲Drives 7 LEDs
LM27966▲Advanced Brightness Control With 12C Interface, Higher Efficiency With Adaptive Gain Charge Pump
LM2793▲Drives 2 LEDs, LLP
LM2795▲Active-High Shutdown Pin
LM3595▲No Boost, LLP
Additional Resources
Application Notes


Block Diagram

click for larger image



Datasheet
RoHS Compliance Information Size in KbytesDate Click link below to Download
LM2794/LM2795 Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control 487
Kbytes		 22-Mar-04 Download
LM2794/LM2795 Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control (Japanese)
 518 Kbytes   Download

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Package Availability, Models, Samples & Pricing
Part NumberPackageFactory Lead TimeModelsSamples &
Electronic
Orders		Budgetary PricingStd
Pack
Size		Package
Marking
Format
TypePinsSpec.MSL
Rating		Peak
Reflow		RoHS
Report		CAD
Symbols		WeeksQtyQty$US each
LM2794EVALCurrent Regulated Switched Capacitor LED Supply with Analog and PWM Brightness ControlFull productionN/A
 
Buy Now 		1+$81.001-
6 weeksN/A
LM2794TLMICRO SMD14NOPB1260RoHS Download Full productionN/A
Samples
Buy Now 		1K+$0.76reel
of
250		XYTT
I LOG
6 weeksN/A
LM2794TLXMICRO SMD14NOPB1260RoHS Download Full productionN/A
 
Buy Now 		1K+$0.76reel
of
3000		XYTT
I LOG
6 weeksN/A

Obsolete Versions

Obsolete PartAlternate Part or SupplierSourceLast Time Buy Date
LM2794BL
NONE
NATIONAL SEMICONDUCTOR
24 Jul 2009
LM2794BLX
NONE
NATIONAL SEMICONDUCTOR
16 Nov 2008

General Description

The LM2794/95 is a fractional CMOS charge-pump that provides four regulated current sources. It accepts an input voltage range from 2.7V to 5.5V and maintains a constant current determined by an external sense resistor.

The LM2794/5 delivers up to 80mA of load current to accommodate four White LEDs. The switching frequency is 325kHz. (min.) to keep the conducted noise spectrum away from sensitive frequencies within portable RF devices.

Brightness can be controlled by both linear and PWM techniques. A voltage between 0V and 3.0V may be applied to the BRGT pin to linearly vary the LED current. Alternatively, a PWM signal can be applied to the SD pin to vary the perceived brightness of the LED. The SD pin reduces the operating current to 2.3µA (typ.) The LM2794 is shut down when the SD pin is low, and the LM2795 is shut down when the SD pin is high.

The LM2794/95 is available in a micro SMD-14 CSP package.

Reliability Metrics

Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
LM2794TLCS065238968520440200011249079519
LM2794TLXCS065238968520440200011249079519

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.


Application Notes

TitleSize in Kbytes Date Click link below to Download
AN-1251: Application Note 1251 Switched Capacitor Circuits Provide Efficient and Functional White LED Drive 55
Kbytes		 26-Sep-02 Download
AN-1218: Application Note 1218 LM2791/2/4/5 Evaluation Board 424
Kbytes		 13-May-04 Download

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More Application Notes

TitleSize in Kbytes Date Click link below to Download
AN-1321: Application Note 1321 LM2796 Evaluation Board 453
Kbytes		 25-May-04 Download
AN-1278: Application Note 1278 LM2793 Evaluation Board 213
Kbytes		 23-Mar-04 Download

If you have trouble printing or viewing PDF file(s), see Printing Problems.

[Information as of 8-Nov-2009]