Application· White LED Display Backlights
· White LED Keypad Backlights
· General Purpose LED LightingPinout
Specifications
| Regulated LEDs |
4 |
| Total LED Current |
120 mA |
| Current Matching |
0.2% |
| Boost Type |
Switched Capacitor Multi-Gain |
| Switching Frequency |
750 kHz |
| Efficiency (peak) |
85 % |
| Input Min Voltage |
3 Volt |
| Input Max Voltage |
5.5 Volt |
| LED Configuration |
Parallel |
| Supply Current |
1.3 mA |
| Switching Type |
Fixed Freq |
| Special Features |
Common anode current sink topology |
| PWM BrightCtrl |
Yes |
| Analog-V BrightCtrl |
No |
| Ambient Light Compensation |
No |
| RGB-LED |
No |
| Temperature Min |
-40 deg C |
| Temperature Max |
85 deg C |
| RegType |
WhiteLED Driver |
| PowerWise |
Yes |
| View Using Catalog |
If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
VIN ...............................................-0.3V to 6.0V
EN, PWM ...........................-0.3V to (VIN + 0.3V)
..........................................w/ 6.0V max
Continuous Power Dissipation
(Note 3) Internally Limited
Junction Temperature
(TJ-MAX-ABS) ...........................................150°C
Storage Temperature Range.... -65°C to 150°C
Lead Temp. (Soldering, 5 sec.)................. 260°C
ESD Rating (Note 4)
Human Body Model ........................................2kV
DescriptionThe LM27952 is a switched capacitor white-LED driver capable of driving up to 4 LEDs with 30mA through each LED. Its 4 tightly regulated current sinks ensure excellent LED current and brightness matching. LED drive current is programmed by an external sense resistor. The LM27952 operates over an input voltage range from 3.0V to 5.5V and requires only four low-cost ceramic capacitors.
The LM27952 provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2, or in a gain of 1. Maximum efficiency is achieved over the input voltage range by actively selecting the proper gain based on the LED forward voltage requirements.
The LM27952 uses constant frequency pre-regulation to minimize conducted noise on the input. It has a fixed 750kHz switching frequency optimized for portable applications. The LM27952 consumes less than 1µA of supply current when shut down.
The LM27952 is available in a 14-pin No-Pullback Leadless Leadframe Package: LLP-14.
Reliability Metrics
| Part Number |
Process |
EFR Reject |
EFR Sample Size |
PPM |
LTA Rejects |
LTA Device Hours |
FITS |
MTTF (Hours) |
| LM27952SD |
CMOS7 |
0 |
16561 |
0 |
0 |
954000 |
4 |
270700104 |
| LM27952SDX |
CMOS7 |
0 |
16561 |
0 |
0 |
954000 |
4 |
270700104 |
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.
Design Tools
| Title |
Size in Kbytes |
Date |
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| Want to Boost Battery Voltage in White LED Apps? |
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View |
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If you have trouble printing or viewing PDF file(s), see Printing Problems.
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More Application Notes
| Title |
Size in Kbytes |
Date |
|
| AN-1218: Application Note 1218 LM2791/2/4/5 Evaluation Board |
424 Kbytes |
13-May-04 |
Download |
| AN-1251: Application Note 1251 Switched Capacitor Circuits Provide Efficient and Functional White LED Drive |
55 Kbytes |
26-Sep-02 |
Download |
If you have trouble printing or viewing PDF file(s), see Printing Problems.
|
The LM27952 is a switched capacitor white-LED driver capable of driving up to 4 LEDs with 30mA through each LED.Its 4 tightly regulated current sinks ensure excellent LED current and brightness matching. LED drive current is programmed by an external sense resistor. The LM27952 operates over an input voltage range from 3.0V to 5.5V and
requires only four low-cost ceramic capacitors.
The LM27952 provides excellent efficiency without the use ofan inductor by operating the charge pump in a gain of 3/2,or in a gain of 1. Maximum efficiency is achieved over the input voltage range by actively selecting the proper gain
based on the LED forward voltage requirements.
The LM27952 uses constant frequency pre-regulation to minimize conducted noise on the input. It has a fixed 750kHz
switching frequency optimized for portable applications. The LM27952 consumes less than 1A of supply current when
shut down.
The LM27952 is available in a 14-pin No-Pullback Leadless Leadframe Package: LLP-14.
LM27952 Data Sheet
