LM2756_0712 NSC [National Semiconductor], LM2756_0712 Datasheet

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LM2756_0712

Manufacturer Part Number
LM2756_0712
Description
Multi-Display Inductorless LED Driver with 32 Exponential Dimming Steps in micro SMD
Manufacturer
NSC [National Semiconductor]
Datasheet
© 2007 National Semiconductor Corporation
LM2756
Multi-Display Inductorless LED Driver with 32 Exponential
Dimming Steps in micro SMD
General Description
The LM2756 is a highly integrated, switched-capacitor, multi-
display LED driver that can drive up to 8 LEDs in parallel with
a total output current of 180mA. Regulated internal current
sources deliver excellent current and brightness matching in
all LEDs.
The LED driver current sinks are split into three independently
controlled groups. The primary group (Group A) can be con-
figured to drive four, five or six LEDs for use in the main phone
display, while the secondary group (Group B) can be config-
ured to drive one, two or three LEDs for driving secondary
displays, keypads and/or indicator LEDs. An additional driver,
D1C, is provided for additional indicator lighting functions.
The device provides excellent efficiency without the use of an
inductor by operating the charge pump in a gain of 3/2 or in
Pass-Mode. The proper gain for maintaining current regula-
tion is chosen, based on LED forward voltage, so that effi-
ciency is maximized over the input voltage range.
The LM2756 is available in National’s tiny 20-bump, 0.4mm
pitch, thin micro SMD package.
Typical Application Circuit
300097
Features
Applications
Drives up to 8 LEDs with up to 30mA of Diode Current
Each
32 Exponential Dimming Steps with 800:1 Dimming Ratio
for Group A (Up to 6 LEDs)
8 Linear Dimming States for Groups B (Up to 3 LEDs) and
D1C (1 LED)
Programmable Auto-Dimming Function
3 Independently Controlled LED Groups Via I
Compatible Interface
Up to 90% Efficiency
Total Solution Size < 21mm
Low Profile 20 Bump micro SMD Package
(1.615mm × 2.015mm × 0.6mm)
0.4% Accurate Current Matching
Internal Soft-Start Limits Inrush Current
True Shutdown Isolation for LED’s
Wide Input Voltage Range (2.7V to 5.5V)
Active High Hardware Enable
Dual Display LCD Backlighting for Portable Applications
Large Format LCD Backlighting
Display Backlighting with Indicator Light
2
30009701
December 5, 2007
www.national.com
2
C

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LM2756_0712 Summary of contents

Page 1

LM2756 Multi-Display Inductorless LED Driver with 32 Exponential Dimming Steps in micro SMD General Description The LM2756 is a highly integrated, switched-capacitor, multi- display LED driver that can drive LEDs in parallel with a total output current ...

Page 2

Connection Diagram Pin Descriptions Bump #s Pin Names TMD20AAA OUT A1, C1, B1, B2 C1+, C1-, C2+, C2- D3, E3,E4, D4 D1A-D4A C4, B4 D53, D62 B3 D1B C3 D1C D2 I SET E1 HWEN ...

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Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. V pin voltage IN SCL, SDIO, HWEN pin voltages I Pin Voltages Dxx Continuous Power Dissipation (Note 3) Junction ...

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Symbol Parameter I Shutdown Supply Current Pin Voltage SET SET I Output Current to Current Set Ratio DxA-B GroupA, GroupB, GroupC SET f Switching Frequency SW t Start-up Time START V HWEN Voltage Thresholds HWEN ...

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Note 10: The maximum total output current for the LM2756 should be limited to 180mA. The total output current can be split among any of the three Groups ( 30mA Max.). Under maximum output current ...

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Typical Performance Characteristics 3.6V; R LEDxA LEDxB LED1C SET LED Drive Efficiency vs Input Voltage Input Current vs Input Voltage GroupB Diode Current vs Input Voltage www.national.com Unless otherwise specified 11.8kΩ; C ...

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GroupA Current Matching vs Input Voltage 6 LEDs GroupB Current Matching vs Input Voltage 3 LEDs GroupB Diode Current vs GroupB Brightness Code GroupA Current Matching vs Input Voltage 30009716 GroupA Diode Current vs GroupA Brightness Code 30009718 GroupC Diode ...

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Quiescent Current in Gain 1.5× vs Input Voltage www.national.com Shutdown Current vs Input Voltage 30009714 8 30009715 ...

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Circuit Description OVERVIEW The LM2756 is a white LED driver system based upon an adaptive 3/2× - 1× CMOS charge pump capable of supplying up to 180mA of total output current. With three separately controlled Groups of constant current sinks, ...

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SDIO line (HIGH) during the acknowl- edge clock pulse. The LM2756 pulls down the SDIO line during the 9th clock pulse, signifying an acknowledge. The LM2756 generates an acknowledge after each byte is re- ceived. After the ...

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Internal Hex Address: 0xA0 (GroupA), 0xB0 (GroupB), 0xC0 (GroupC) Note: DxA4-DxA0, D53, D62: Sets Brightness for DxA pins (GroupA). 11111=Fullscale DxB2-DxB0: Sets Brightness for DxB pins (GroupB). 111=Fullscale DxC2-DxC0: Sets Brightness for D1C pin. 111 = Fullscale Full-Scale Current set ...

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GroupB and GroupC(D1C) have 8 ana- log current levels. Please refer to the Compatible Interface section of this datasheet for detailed instructions on how to adjust the bright- ness control registers. LED CURRENT ...

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LED current). The efficiency of the LM2756 can be predicted as follow × N × I LEDTOTAL LEDA A (V × N × LEDB B LEDB LEDC × ...

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Physical Dimensions www.national.com inches (millimeters) unless otherwise noted TMD20AAA: 20 Bump 0.4mm micro SMD X1 = 1.615mm X2 = 2.015mm X3 = 0.6mm 14 ...

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Notes 15 www.national.com ...

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