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National LM2756 Data Handbook / Specifications

Summary

The LM2756 is a highly integrated, inductorless LED driver designed for complex display applications requiring precise illumination control. This component can simultaneously drive up to 8 LEDs across independently configurable groups—ideal for main displays, keypads, and indicator lights. It offers advanced features such as 32 exponential dimming steps and high efficiency in an ultra-compact micro SMD package (2.7V–5.5V input). The manual provides comprehensive technical specifications, pin descriptions, and application guidelines to ensure seamless implementation in portable electronics requiring superior LCD backlighting or multi-display functionality.

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lti-D is la In to rle riv r w ith tia l D im in te in ic ro

December 5, 2007

LM2756 Multi-Display Inductorless LED Driver with 32 Exponential Dimming Steps in micro SMD General Description Features The LM2756 is a highly integrated, switched-capacitor, multi- Drives up to 8 LEDs with up to 30m A of Diode Current display LED driver that can drive up to 8 LEDs in parallel with Each a total output current of 180m A. Regulated internal current 32 Exponential Dimming Steps with 800:1 Dimming Ratio sources deliver excellent current and brightness matching in for Group A (Up to 6 LEDs) all LEDs.

8 Linear Dimming States for Groups B (Up to 3 LEDs) and

The LED driver current sinks are split into three independently D1C (1 LED) controlled groups. The primary group (Group A) can be con- Programmable Auto-Dimming Function figured to drive four, five or six LEDs for use in the main phone

3 Independently Controlled LED Groups Via I2C

display, while the secondary group (Group B) can be config-

Compatible Interface

ured to drive one, two or three LEDs for driving secondary

Up to 90% Efficiency

displays, keypads and/or indicator LEDs. An additional driver,

Total Solution Size < 21mm2

D1C, is provided for additional indicator lighting functions.

Low Profile 20 Bump micro SMD Package

The device provides excellent efficiency without the use of an

(1.615mm × 2.015mm × 0.6mm)

inductor by operating the charge pump in a gain of 3/2 or in

Pass-Mode. The proper gain for maintaining current regula- 0.4% Accurate Current Matching

tion is chosen, based on LED forward voltage, so that effi- Internal Soft-Start Limits Inrush Current ciency is maximized over the input voltage range.

True Shutdown Isolation for LED’s

The LM2756 is available in National’s tiny 20-bump, 0.4mm

Wide Input Voltage Range (2.7V to 5.5V)

pitch, thin micro SMD package.

Active High Hardware Enable

Applications Dual Display LCD Backlighting for Portable Applications Large Format LCD Backlighting Display Backlighting with Indicator Light

Typical Application Circuit

© 2007 National Semiconductor Corporation www.national.com

Page Summary Contents For National LM2756 Data Handbook / Specifications

Page 1 lti-D is la In to rle riv r w ith tia l D im in te in ic ro December 5, 2007 LM2756 Multi-Display Inductorless LED Driver with 32 Exponential Dimming Steps in micro SMD General Description Features Th...
Page 2 Minimum Layout Connection Diagram 20 Bump micro SMD Package NS Package Number TMD20AAA Pin Descriptions Bump #s Pin Names Pin Descriptions TMD20AAA A3 VIN Input voltage. Input range: 2.7V to 5.5V. A2 ...
Page 3 Absolute Maximum Ratings (Notes 1, 2) Operating Rating If Military/Aerospace specified devices are required, (Notes 1, 2) please contact the National Semiconductor Sales Office/ Input Voltage Range 2....
Page 4 Symbol Parameter Condition Min Typ Max Units ISD Shutdown Supply Current All ENx bits = &quot;0&quot; 3.7 5.5 µA VSET ISET Pin Voltage 2.7V ≤ VIN ≤ 5.5V 1.25 IDx A-B-C / Output Current to Current Set ...
Page 5 Note 10: The maximum total output current for the LM2756 should be limited to 180m A. The total output current can be split among any of the three Groups (IDx A = IDx B = IDx C = 30m A Max.). Under ma...
Page 6 Typical Performance Characteristics Unless otherwise specified: TA = 25°C; VIN = 3.6V; VHWEN = VIN; VLEDx A = VLEDx B = VLED1C = 3.6V; RSET = 11.8kΩ; C1=C2= CIN = CVOUT = 1µF; ENA = ENB = ENC = '1'. L...
Page 7 Group A Current Matching vs Input Voltage Group A Current Matching vs Input Voltage 6 LEDs 4 LEDs Group B Current Matching vs Input Voltage Group A Diode Current vs Group A Brightness Code 3 LEDs Grou...
Page 8 Quiescent Current in Gain 1.5× vs Input Voltage Shutdown Current vs Input Voltage www.national.com
Page 9 ISTERS section of this datasheet for more information re- Circuit Description garding the delay ranges. OVERVIEW HWEN Pin The LM2756 is a white LED driver system based upon an The LM2756 has a hardwar...
Page 10 master releases the SDIO line (HIGH) during the acknowl- bit which is a data direction bit (R/W). The LM2756 address edge clock pulse. The LM2756 pulls down the SDIO line is 36h. For the eighth bit, a...
Page 11 Internal Hex Address: 0x A0 (Group A), 0x B0 (Group B), 0x C0 (Group C) Note: Dx A4-Dx A0, D53, D62: Sets Brightness for Dx A pins (Group A). 11111=Fullscale Dx B2-Dx B0: Sets Brightness for Dx B pins...
Page 12 to 32 different levels. Group B and Group C(D1C) have 8 ana- k HR – Headroom constant. This parameter models the mini- log current levels. mum voltage required to be present across the current sinks f...
Page 13 current (total LED current). The efficiency of the LM2756 can dissipation and/or poor thermal resistance causes the junc- be predicted as follow: tion temperature to exceed 105°C. PLEDTOTAL = (VLEDA ×...
Page 14 Physical Dimensions inches (millimeters) unless otherwise noted TMD20AAA: 20 Bump 0.4mm micro SMD X1 = 1.615mm X2 = 2.015mm X3 = 0.6mm www.national.com
Page 15 Notes www.national.com
Page 16 lt i- is la In to rl ri it ti l D im in te in ic ro Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifi...

Manual Details

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Frequently Asked Questions

How many dimming steps does the LM2756 offer?

It provides 32 Exponential Dimming Steps with an improvement ratio up to 800:1.

What is the operational input voltage range for this driver?

The device operates within an input voltage range of 2.7V to 5.5V.

Can I control multiple LED areas separately?

Yes, it supports three independently controlled groups: Group A (primary), Group B (secondary), and a separate indicator LED.

What physical package is used for this driver?

It comes in a low profile 20-bump micro SMD Package (1.615mm × 2.015mm × 0.6mm).

What ESD precautions are necessary when installing the device?

All integrated circuits must be handled with appropriate ESD precautions, specifically Human Body Model 2.0kV.