AS3688-T

AS3688-T Datasheet

General Description 4 Driving LEDs for Mobile Backlight Applications 4 LED Configuration Nomenclature 5 Product 6 Choosing the LED Congiguration 8 LED Configurations for 8 LED Configurations for DCDC 10 DCDC 12 AS3687xm/75/76 DCDC 12 AS3677 DCDC 13 AS3490/AS3492 DCDC 14 High Voltage Current Sink Overview 15 General DCDC Application Component 15 Single String Solutions 16 Single String Solutions with higher Forward Voltages 18 Multiple String Solutions 20 Multiple Strings for Tablets 21 What is the best 22 Increasing Efficiency in light load conditions 24 Driving the DCDC with Serial 25 Dimension of the external 25 Conclusion 27 Design Examples 28 Smartphone with Display 28 Smartphone with Display 30 Mid-range Smartphone, Backlight, Keypad, Torch and ALS 31 Table with 7Sx6 Configuration 42 LEDs + ALS 32 Smartphone backlight with higher Currents 32 Smartphone backlight + Button Backlight & ALS 33 7" Tablet Backlight 34 Headlamp for ebooks or e-ink 35 Feature phone - low size Backlight + 2x RGB LEDs 36 Feature phone - high efficiency backlight + 2x RGB 36 Contact 37

Part	Datasheet
AS3688-T	AS3688-T (pdf)

Related Parts	Information
AS3688	AS3688

PDF Datasheet Preview
Application Note DN[Document ID] Mobile Backlight Selection Guide For ams Lightning Management Units and Backlight Drivers ams Application Note [v1-02] 2014-Jul-18 Page 1 Document Feedback Mobile Backlight Selection Guide Content Guide 1 2 3 4 5 6 7 8 9 10 General Description 4 Driving LEDs for Mobile Backlight Applications 4 LED Configuration Nomenclature 5 Product 6 Choosing the LED Congiguration 8 LED Configurations for 8 LED Configurations for DCDC 10 DCDC 12 AS3687xm/75/76 DCDC 12 AS3677 DCDC 13 AS3490/AS3492 DCDC 14 High Voltage Current Sink Overview 15 General DCDC Application Component 15 Single String Solutions 16 Single String Solutions with higher Forward Voltages 18 Multiple String Solutions 20 Multiple Strings for Tablets 21 What is the best 22 Increasing Efficiency in light load conditions 24 Driving the DCDC with Serial 25 Dimension of the external 25 Conclusion 27 Design Examples 28 Smartphone with Display 28 Smartphone with Display 30 Mid-range Smartphone, Backlight, Keypad, Torch and ALS 31 Table with 7Sx6 Configuration 42 LEDs + ALS 32 Smartphone backlight with higher Currents 32 Smartphone backlight + Button Backlight & ALS 33 7" Tablet Backlight 34 Headlamp for ebooks or e-ink 35 Feature phone - low size Backlight + 2x RGB LEDs 36 Feature phone - high efficiency backlight + 2x RGB 36 Contact 37 ams Application Note [v1-02] 2014-Jul-18 Page 2 Document Feedback Mobile Backlight Selection Guide Copyrights & 38 ams Application Note [v1-02] 2014-Jul-18 Page 3 Document Feedback Mobile Backlight Selection Guide 1 General Description This guide enables the determination which LED driver product, LED configuration, and external component selection will give the best output in terms of efficiency and solution size for mobile lightning applications. 2 Driving LEDs for Mobile Backlight Applications Depending on the application or display size, the amount of LEDs is different. For smartphone and feature phones the LED requirements are quite similar. LEDs are used in the current range of 2~30mA. The bigger the display gets the more LEDs are needed, also the more pixels the display contains for higher resolution the more LEDs are required to brighten up the display. Typically all LEDs inside the display are driven with the same amount of current. Figure 1 Market Research of several on the market available phones display size vs. LED count ams Application Note [v1-02] 2014-Jul-18 Page 4 Document Feedback Mobile Backlight Selection Guide Figure 2 Example of a smartphone display with 10 LEDs 3 LED Configuration Nomenclature The ams display nomenclature can be used for any kind of display or non-display LED configurations. The nomenclature explains the relation of serial LEDs in a string to the amount of parallel strings. First number is the amount of LEDs in series. Second number is the amount of LED strings in parallel For example 6Sx2 = 6 LEDs in one string with 2 parallel strings Figure 3 ams Display Nomenclature Examples ams Application Note [v1-02] 2014-Jul-18 Page 5 Document Feedback Mobile Backlight Selection Guide 4 Product Overview Figure 4 Product Overview Keypad Display Camera Lighting Inductive DCDC Chargepump # Current Sinks ALS DLS Flash Current Flash Timeout Indicator LED Supply LDOs LED Test LED Dimming RGB Pattern Audio Sync ams Application Note [v1-02] 2014-Jul-18 AS3490 AS3492 AS3675 AS3676 AS3677 AS3687 AS3688 AS3689 XM 400mA 50mA 150mA 400mA 150mA 900mA 150mA

PDF Datasheet Preview

Application Note

DN[Document ID]

Mobile Backlight Selection Guide

For ams Lightning Management Units and Backlight Drivers
ams Application Note [v1-02] 2014-Jul-18

Page 1 Document Feedback

Mobile Backlight Selection Guide

Content Guide
1 2 3 4 5 6 7 8 9 10

General Description 4 Driving LEDs for Mobile Backlight Applications 4 LED Configuration Nomenclature 5 Product 6 Choosing the LED Congiguration 8 LED Configurations for 8 LED Configurations for DCDC 10 DCDC 12 AS3687xm/75/76 DCDC 12 AS3677 DCDC 13 AS3490/AS3492 DCDC 14 High Voltage Current Sink Overview 15 General DCDC Application Component 15 Single String Solutions 16 Single String Solutions with higher Forward Voltages 18 Multiple String Solutions 20 Multiple Strings for Tablets 21 What is the best 22 Increasing Efficiency in light load conditions 24 Driving the DCDC with Serial 25 Dimension of the external 25 Conclusion 27 Design Examples 28 Smartphone with Display 28 Smartphone with Display 30 Mid-range Smartphone, Backlight, Keypad, Torch and ALS 31 Table with 7Sx6 Configuration 42 LEDs + ALS 32 Smartphone backlight with higher Currents 32 Smartphone backlight + Button Backlight & ALS 33 7" Tablet Backlight 34 Headlamp for ebooks or e-ink 35 Feature phone - low size Backlight + 2x RGB LEDs 36 Feature phone - high efficiency backlight + 2x RGB 36 Contact 37
ams Application Note [v1-02] 2014-Jul-18

Page 2 Document Feedback

Mobile Backlight Selection Guide

Copyrights & 38
ams Application Note [v1-02] 2014-Jul-18

Page 3 Document Feedback

Mobile Backlight Selection Guide
1 General Description

This guide enables the determination which LED driver product, LED configuration, and external component selection will give the best output in terms of efficiency and solution size for mobile lightning applications.
2 Driving LEDs for Mobile Backlight Applications

Depending on the application or display size, the amount of LEDs is different. For smartphone and feature phones the LED requirements are quite similar. LEDs are used in the current range of 2~30mA. The bigger the display gets the more LEDs are needed, also the more pixels the display contains for higher resolution the more LEDs are required to brighten up the display. Typically all LEDs inside the display are driven with the same amount of current.

Figure 1 Market Research of several on the market available phones display size vs. LED count
ams Application Note [v1-02] 2014-Jul-18

Page 4 Document Feedback

Mobile Backlight Selection Guide

Figure 2 Example of a smartphone display with 10 LEDs
3 LED Configuration Nomenclature

The ams display nomenclature can be used for any kind of display or non-display LED configurations. The nomenclature explains the relation of serial LEDs in a string to the amount of parallel strings. First number is the amount of LEDs in series. Second number is the amount of LED strings in parallel For example 6Sx2 = 6 LEDs in one string with 2 parallel strings Figure 3 ams Display Nomenclature Examples
ams Application Note [v1-02] 2014-Jul-18

Page 5 Document Feedback

Mobile Backlight Selection Guide
4 Product Overview

Figure 4 Product Overview

Keypad Display Camera

Lighting Inductive DCDC Chargepump # Current Sinks ALS DLS Flash Current Flash Timeout Indicator LED Supply LDOs LED Test LED Dimming RGB Pattern Audio Sync
ams Application Note [v1-02] 2014-Jul-18

AS3490 AS3492 AS3675 AS3676 AS3677 AS3687 AS3688 AS3689 XM
400mA 50mA
150mA 400mA
150mA
900mA 150mA

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Datasheet ID: AS3688-T 519800