SNVS606L June   2009  – December 2014 LM3530

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. I2C Device Options
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 I2C-Compatible Timing Requirements (SCL, SDA)
    7. 7.7 Simple Interface Timing
    8. 7.8 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Start-Up
      2. 8.3.2  Light Load Operation
      3. 8.3.3  Ambient Light Sensor
      4. 8.3.4  ALS Operation
      5. 8.3.5  ALS Averaging Time
        1. 8.3.5.1 Averager Operation
      6. 8.3.6  Zone Boundary Settings
      7. 8.3.7  Zone Boundary Trip Points and Hysteresis
      8. 8.3.8  Minimum Zone Boundary Settings
      9. 8.3.9  LED Current Control
      10. 8.3.10 Exponential or Linear Brightness Mapping Modes
      11. 8.3.11 PWM Input Polarity
      12. 8.3.12 I2C-Compatible Current Control Only
      13. 8.3.13 Simple Enable Disable With PWM Current Control
      14. 8.3.14 Ambient Light Current Control
      15. 8.3.15 Ambient Light Current Control + PWM
      16. 8.3.16 Interrupt Output
      17. 8.3.17 Overvoltage Protection
      18. 8.3.18 Hardware Enable
      19. 8.3.19 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown
      2. 8.4.2 I2C Mode
      3. 8.4.3 PWM + I2C Mode
      4. 8.4.4 ALS Mode
      5. 8.4.5 Simple Enable Mode
    5. 8.5 Programming
      1. 8.5.1 I2C-Compatible Interface
        1. 8.5.1.1 Start and Stop Condition
        2. 8.5.1.2 I2C-Compatible Address
        3. 8.5.1.3 Transferring Data
    6. 8.6 Register Maps
      1. 8.6.1 Register Descriptions
        1. 8.6.1.1 General Configuration Register (GP)
        2. 8.6.1.2 ALS Configuration Register
        3. 8.6.1.3 Brightness Ramp Rate Register
        4. 8.6.1.4 ALS Zone Information Register
        5. 8.6.1.5 ALS Resistor Select Register
        6. 8.6.1.6 Brightness Control Register
        7. 8.6.1.7 Zone Boundary Register
        8. 8.6.1.8 Zone Target Registers
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 LED Current Setting/Maximum LED Current
        2. 9.2.2.2 Maximum Duty Cycle
        3. 9.2.2.3 Peak Current Limit
        4. 9.2.2.4 Output Voltage Limitations
        5. 9.2.2.5 Output Capacitor Selection
        6. 9.2.2.6 Inductor Selection
        7. 9.2.2.7 Diode Selection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Output Capacitor Placement
      2. 11.1.2 Schottky Diode Placement
      3. 11.1.3 Inductor Placement
      4. 11.1.4 Input Capacitor Selection and Placement
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LM3530 incorporates a 40-V (maximum output) boost, a single current sink, and a dual ambient light sensor interface. The maximum boost output voltage is 40 V (min) for the LM3530-40 version. The LM3530 boost will drive the output voltage to whatever voltage necessary to maintain 400mV at the ILED input. The 40-V max output typically allows the LM3530 to drive from 2 series up to 12 series LEDs (3.2V max voltage per LED). For applications that do not use one or both of the ALS inputs, the ALS input can be connected to GND or left floating.

9.2 Typical Application

30086601.gifFigure 49. LM3530 Typical Application

9.2.1 Design Requirements

Example requirements for typical voltage inverter applications:

Table 12. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input voltage range 2.7 V to 5.5 V
Output current 0 mA to 30 mA
Boost switching frequency 500 kHz

Table 13. Application Circuit Component List

COMPONENT MANUFACTURER PART NUMBER VALUE SIZE CURRENT/VOLTAGE RATING
L TDK VLF3014ST100MR82 10 µH 3 mm × 3 mm × 1.4 mm ISAT = 820 mA
COUT Murata GRM21BR71H105KA12 1 µF 0805 50 V
CIN Murata GRM188B31A225KE33 2.2 µF 0603 10 V
D1 Diodes Inc. B0540WS Schottky SOD-323 40 V/500 mA
ALS1 Avago APDS-9005 Ambient Light Sensor 1.6 mm x 1.5 mm × 0.6 mm 0 to 1100 Lux
ALS2 Avago APDS-9005 Ambient Light Sensor 1.6 mm x 1.5 mm × 0.6 mm 0 to 1100 Lux

9.2.2 Detailed Design Procedure

9.2.2.1 LED Current Setting/Maximum LED Current

The maximum LED current is restricted by the following factors: the maximum duty cycle that the boost converter can achieve, the peak current limitations, and the maximum output voltage.

9.2.2.2 Maximum Duty Cycle

The LM3530 can achieve up to typically 94% maximum duty cycle. Two factors can cause the duty cycle to increase: an increase in the difference between VOUT and VIN and a decrease in efficiency. This is shown by Equation 12:

Equation 12. 30086635.gif

For a 9-LED configuration VOUT = (3.6 V x 9LED + VHR) = 33 V operating with η = 70% from a 3-V battery, the duty cycle requirement would be around 93.6%. Lower efficiency or larger VOUT to VIN differentials can push the duty cycle requirement beyond 94%.

9.2.2.3 Peak Current Limit

The LM3530 boost converter has a peak current limit for the internal power switch of 839 mA typical (739 mA minimum). When the peak switch current reaches the current limit, the duty cycle is terminated resulting in a limit on the maximum output current and thus the maximum output power the LM3530 can deliver. Calculate the maximum LED current as a function of VIN, VOUT, L, efficiency (η) and IPEAK as:

Equation 13. 30086605.gif

where

9.2.2.4 Output Voltage Limitations

The LM3530 has a maximum output voltage of 41 V typical (40 V minimum) for the LM3530-40 version and 24 V typical (23.6 V minimum) for the LM3530-25 version. When the output voltage rises above this threshold (VOVP) the overvoltage protection feature is activated and the duty cycle is terminated. Switching will cease until VOUT drops below the hysteresis level (typically 1 V below VOVP). For larger numbers of series connected LEDs the output voltage can reach the OVP threshold at larger LED currents and colder ambient temperatures. Typically white LEDs have a –3mV/°C temperature coefficient.

9.2.2.5 Output Capacitor Selection

The LM3530’s output capacitor has two functions: filtering of the boost converters switching ripple, and to ensure feedback loop stability. As a filter, the output capacitor supplies the LED current during the boost converters on time and absorbs inductor energy during the switch off time. This causes a sag in the output voltage during the on time and a rise in the output voltage during the off time. Because of this, the output capacitor must be sized large enough to filter the inductor current ripple that could cause the output voltage ripple to become excessive. As a feedback loop component, the output capacitor must be at least 1 µF and have low ESR otherwise the LM3530 boost converter can become unstable. This requires the use of ceramic output capacitors. Table 14 lists part numbers and voltage ratings for different output capacitors that can be used with the LM3530.

Table 14. Recommended Input/Output Capacitors

MANUFACTURER PART NUMBER VALUE (µF) SIZE RATING (V) DESCRIPTION
Murata GRM21BR71H105KA12 1 0805 50 COUT
Murata GRM188B31A225KE33 2.2 0805 10 CIN
TDK C1608X5R0J225 2.2 0603 6.3 CIN

9.2.2.6 Inductor Selection

The LM3530 is designed to work with a 10-µH to 22-µH inductor. When selecting the inductor, ensure that the saturation rating for the inductor is high enough to accommodate the peak inductor current. Equation 14 and Equation 15 calculate the peak inductor current based upon LED current, VIN, VOUT, and efficiency.

Equation 14. 30086629.gif

where:

Equation 15. 30086630.gif

When choosing L, the inductance value must also be large enough so that the peak inductor current is kept below the LM3530 switch current limit. This forces a lower limit on L given by Equation 16.

Equation 16. 30086631.gif

ISW_MAX is given in , efficiency (η) is shown in the Application Curves, and ƒSW is typically 500 kHz.

Table 15. Suggested Inductors

MANUFACTURER PART NUMBER VALUE (µH) SIZE (mm) RATING (mA) DC RESISTANCE (Ω)
TDK VLF3014ST-100MR82 10 2.8 × 3 × 1.4 820 0.25
TDK VLF3010ST-220MR34 22 2.8 × 3 × 1 340 0.81
TDK VLF3010ST-100MR53 10 2.8 × 3 × 1 530 0.41
TDK VLF4010ST-100MR80 10 2.8 × 3 × 1 800 0.25
TDK VLS252010T-100M 10 2.5 × 2 × 1 650 0.71
Coilcraft LPS3008-103ML 10 2.95 × 2.95 × 0.8 520 0.65
Coilcraft LPS3008-223ML 22 2.95 × 2.95 × 0.8 340 1.5
Coilcraft LPS3010-103ML 10 2.95 × 2.95 × 0.9 550 0.54
Coilcraft LPS3010-223ML 22 2.95 × 2.95 × 0.9 360 1.2
Coilcraft XPL2010-103ML 10 1.9 × 2 × 1 610 0.56
Coilcraft EPL2010-103ML 10 2 × 2 × 1 470 0.91
TOKO DE2810C-1117AS-100M 10 3 × 3.2 × 1 600 0.46

9.2.2.7 Diode Selection

The diode connected between SW and OUT must be a Schottky diode and have a reverse breakdown voltage high enough to handle the maximum output voltage in the application. Table 16 lists various diodes that can be used with the LM3530. For 25-V OVP devices a 30-V Schottky is adequate. For 40-V OVP devices, a 40-V Schottky diode should be used.

Table 16. Suggested Diodes

MANUFACTURER PART NUMBER VALUE SIZE (mm) RATING
Diodes Inc B0540WS Schottky SOD-323 (1.7 × 1.3) 40 V/500 mA
Diodes Inc SDM20U40 Schottky SOD-523 (1.2 × 0.8 × 0.6) 40 V/200 mA
On Semiconductor NSR0340V2T1G Schottky SOD-523 (1.2 × 0.8 × 0.6) 40 V/250 mA
On Semiconductor NSR0240V2T1G Schottky SOD-523 (1.2 × 0.8 × 0.6) 40 V/250 mA

9.2.3 Application Curves

30086651.png
IFULL_SCALE = 19 mA
Figure 50. Efficiency vs VIN
30086653.png
IFULL_SCALE = 19 mA
Figure 52. Efficiency vs VIN
30086654.png
Figure 54. Efficiency vs ILED
30086652.png
IFULL_SCALE = 19 mA
Figure 51. Efficiency vs VIN
30086654.png
Figure 53. Efficiency vs ILED
30086655.png
Figure 55. Efficiency vs ILED