SNOSC68C April   2012  – September 2015 LM3533

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 I2C Timing Requirements
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Control Bank Mapping
        1. 7.3.1.1 High-Voltage Control Banks (A/B)
        2. 7.3.1.2 Low-Voltage Control Banks (C, D, E, And F)
      2. 7.3.2 Pattern Generator
      3. 7.3.3 Ambient Light Sensor Interface
      4. 7.3.4 PWM Input
      5. 7.3.5 HWEN Input
      6. 7.3.6 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1  High-Voltage Boost Converter
        1. 7.4.1.1 High-Voltage Current Sinks (HVLED1 And HVLED2)
        2. 7.4.1.2 High-Voltage Current String Biasing
        3. 7.4.1.3 Boost Switching-Frequency Select
      2. 7.4.2  Integrated Charge Pump
        1. 7.4.2.1 Charge Pump Disabled
        2. 7.4.2.2 Automatic Gain
        3. 7.4.2.3 Automatic Gain (Flying Capacitor Detection)
        4. 7.4.2.4 1× Gain
        5. 7.4.2.5 2× Gain
        6. 7.4.2.6 Low-Voltage Current Sinks (LVLED1 to LVLED5)
        7. 7.4.2.7 Low-Voltage LED Biasing
      3. 7.4.3  LED Current Mapping Modes
        1. 7.4.3.1 Exponential Mapping
        2. 7.4.3.2 Linear Mapping
      4. 7.4.4  LED Current Ramping
        1. 7.4.4.1 Start-Up/Shutdown Ramp
        2. 7.4.4.2 Run-Time Ramp
      5. 7.4.5  Brightness Register Current Control
      6. 7.4.6  PWM Control
        1. 7.4.6.1 PWM Input Frequency Range
        2. 7.4.6.2 PWM Input Polarity
      7. 7.4.7  ALS Current Control
        1. 7.4.7.1 ALS Brightness Zones (Zone Boundaries)
        2. 7.4.7.2 Zone Boundary Hysteresis
        3. 7.4.7.3 Zone Target Registers (ALSM1, ALSM2, ALSM3)
        4. 7.4.7.4 PWM Input in ALS Mode
      8. 7.4.8  ALS Functional Blocks
        1. 7.4.8.1  ALS Input
        2. 7.4.8.2  Analog Output Ambient Light Sensors (ALS Gain Setting Resistors)
        3. 7.4.8.3  PWM Output Ambient Light Sensors (Internal Filtering)
        4. 7.4.8.4  Internal 8-Bit ADC
        5. 7.4.8.5  ALS Averager
        6. 7.4.8.6  Initializing the ALS
        7. 7.4.8.7  ALS Algorithms
        8. 7.4.8.8  ALS Rules
        9. 7.4.8.9  Direct ALS Control
        10. 7.4.8.10 Up-Only Control
        11. 7.4.8.11 Down-Delay Control
      9. 7.4.9  Pattern Generator
        1. 7.4.9.1 Delay Time
        2. 7.4.9.2 Rise Time
        3. 7.4.9.3 Fall Time
        4. 7.4.9.4 High Period
        5. 7.4.9.5 Low Period
        6. 7.4.9.6 Low-Level Brightness
        7. 7.4.9.7 High-Level Brightness
        8. 7.4.9.8 ALS Controlled Pattern Current
        9. 7.4.9.9 Interrupt Output Mode
      10. 7.4.10 Fault Flags/Protection Features
        1. 7.4.10.1 Open LED String (HVLED)
        2. 7.4.10.2 Shorted LED String (HVLED)
        3. 7.4.10.3 Open LED (LVLED)
        4. 7.4.10.4 Shorted LED (LVLED)
        5. 7.4.10.5 Overvoltage Protection (Inductive Boost)
        6. 7.4.10.6 Current Limit (Inductive Boost)
        7. 7.4.10.7 Current Limit (Charge Pump)
    5. 7.5 Programming
      1. 7.5.1 I2C-Compatible Interface
        1. 7.5.1.1 Start and Stop Conditions
        2. 7.5.1.2 I2C-Compatible Address
        3. 7.5.1.3 Transferring Data
    6. 7.6 Register Maps
      1. 7.6.1 LM3533 Register Descriptions
        1. 7.6.1.1 Pattern Generator Registers
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Boost Converter Maximum Output Power (Boost)
        2. 8.2.2.2 Peak Current Limited
        3. 8.2.2.3 Output Voltage Limited
        4. 8.2.2.4 Maximum Output Power (Charge Pump)
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Boost
        1. 10.1.1.1 Boost Output Capacitor Selection and Placement
        2. 10.1.1.2 Schottky Diode Placement
        3. 10.1.1.3 Inductor Placement
        4. 10.1.1.4 Boost Input Capacitor Selection and Placement
      2. 10.1.2 Charge Pump
        1. 10.1.2.1 Flying Capacitor (CP)
        2. 10.1.2.2 Output Capacitor (CPOUT)
        3. 10.1.2.3 Charge Pump Input Capacitor Placement
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Related Documentation
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 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.

8.1 Application Information

The LM3533 is a dual-string (up to 40 V at up to 30 mA) backlight driver with five integrated low voltage indicator current sinks. The current through any LED can be controlled by the I2C bus, the PWM input, or via an external ambient light sensor. Any low voltage current sink can be made to blink via a programmable pattern. The programmable pattern can have variable high pulse time, low pulse time, delay from start, high time current, low time current, and ramp rates. The device operates from a typical VIN from 2.7 V to 5.5 V, and an ambient temperature range of -40°C to +85°C.

8.2 Typical Application

LM3533 30135701.gif Figure 37. LM3533 Typical Application

8.2.1 Design Requirements

For typical lighting power-source applications, use the parameters listed in Table 48.

Table 48. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Minimum input voltage 2.7 V
Minimum output voltage 0.6 V
Output current 0 to 750 mA
Switching frequency 2.4 MHz (typical)

8.2.2 Detailed Design Procedure

Table 49. Application Circuit Component List

COMPONENT MANUFACTURER VALUE PART NUMBER SIZE (mm) CURRENT/VOLTAGE RATING (RESISTANCE)
L TDK 10 µH VLF302512MT-100M 2.5 x 3 x 1.2 620 mA/0.25 Ω
COUT TDK 1 µF C2012X5R1H105 0805 50 V
CIN TDK 2.2 µF C1005X5R1A225 0402 10 V
CPOUT/CP TDK 1 µF C1005X5R1A105 0402 10 V
Diode On-Semi Schottky NSR0240V2T1G SOD-523 40 V, 250 mA

8.2.2.1 Boost Converter Maximum Output Power (Boost)

The LM3533 maximum output power is governed by two factors: the peak current limit (ICL = 880 mA minimum), and the maximum output voltage (VOVP). When the application causes either of these limits to be reached, it is possible that the proper current regulation and matching between LED current strings may not be met.

8.2.2.2 Peak Current Limited

In the case of a peak current limited situation, when the peak of the inductor current hits the LM3533 current limit, the NFET switch turns off for the remainder of the switching period. If this happens each switching cycle the LM3533 regulates the peak of the inductor current instead of the headroom across the current sinks. This can result in the dropout of the boost output connected current sinks, and the LED current dropping below its programmed level.

The peak current in a boost converter is dependent on the value of the inductor, total LED current in the boost (IOUT), the boost output voltage (VOUT) (which is the highest voltage LED string + 0.4 V regulated headroom voltage), the input voltage (VIN), the switching frequency, and the efficiency (Output Power/Input Power). Additionally, the peak current is different depending on whether the inductor current is continuous during the entire switching period (CCM), or discontinuous (DCM) where it goes to 0 before the switching period ends. For Continuous Conduction Mode the peak inductor current is given by:

Equation 16. LM3533 30135729.gif

For DCM the peak inductor current is given by:

Equation 17. LM3533 30135730.gif

To determine which mode the circuit is operating in (CCM or DCM) it is necessary to perform a calculation to test whether the inductor current ripple is less than the anticipated input current (IIN). If ΔIL is less than IIN then the device is operating in CCM. If ΔIL is greater than IIN then the device is operating in DCM.

Equation 18. LM3533 30135731.gif

Typically at currents high enough to reach the LM3533 device's peak current limit, the device is operating in CCM. When choosing the switching frequency and the inductor value, Equation 16 and Equation 17 must be used to ensure that IPEAK stays below ICL_MIN (see Electrical Characteristics).

8.2.2.3 Output Voltage Limited

In the case of a output voltage limited situation, when the boost output voltage hits the LM3533 OVP threshold, the NFET turns off and stays off until the output voltage falls below the hysteresis level (typically 1 V below the OVP threshold). This results in the boost converter regulating the output voltage to the programmed OVP threshold (16 V, 24 V, 32 V, or 40 V), causing the current sinks to go into dropout. The default OVP threshold is set at 16 V. For LED strings higher than typically 4 series LEDs, the OVP has to be programmed higher after power-up or after a HWEN reset.

8.2.2.4 Maximum Output Power (Charge Pump)

The maximum output power available from the LM3533 charge pump is determined by the maximum output voltage available from the charge pump. In 1× gain the charge pump operates in Pass Mode so that the voltage at CPOUT tracks VIN (less the drop across the charge pumps pass switch). In this case the maximum output power is given as:

Equation 19. LM3533 30135793.gif

where

  • RCP is the resistance from IN to CPOUT
  • ILVLED_TOTAL is the maximum programmed current in the LVLED strings.

In 2× gain the voltage at CPOUT (VCPOUT_2X) is regulated to typically 4.4 V. In this case the maximum output power is given by:

Equation 20. LM3533 30135794.gif

Equation 19 and Equation 20 both assume there is sufficient headroom at the top side of the low-voltage current sinks to ensure the LED current remains in regulation (VHR_LV) in the Electrical Characteristics.

8.2.3 Application Curves

VIN = 3.6 V, LEDs are WLEDs part number SML-312WBCW(A), typical application circuit with L = TDK (VLF302512, 4.7 µH, 10 µH, 22 µH where specified), Schottky = On-Semi (NSR0240V2T1G), TA = 25°C, unless otherwise specified. Efficiency is given as VOUT × (IHVLED1 + IHVLED2)/(VIN × IIN); matching curves are given as (ΔILED_MAX/ILED_AVE).
LM3533 30135747_nosc68.gif
L = 22 µH 20 mA/String ƒSW = 500 kHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9 (LEDs)
Figure 38. Efficiency vs VIN, Dual String
LM3533 30135749_nosc68.gif
L = 22 µH 20 mA/String ƒSW = 500 kHz
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 40. Efficiency vs VIN, Single String
LM3533 30135751_nosc68.gif
L = 10 µH 20 mA/String ƒSW = 500 kHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9 (LEDs)
Figure 42. Efficiency vs VIN, Dual String
LM3533 30135753_nosc68.gif
L = 10 µH 20 mA/String ƒSW = 500 kHz
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 44. Efficiency vs VIN, Single String
LM3533 30135745_nosc68.gif
L = 4.7 µH 20 mA/String ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9 (LEDs)
Figure 46. Efficiency vs VIN, Dual String
LM3533 30135758.gif
L = 22 µH VIN = 3.6 V ƒSW = 500 kHz
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 48. Efficiency vs ILED
LM3533 30135756.gif
L = 10 µH VIN = 3.6 V ƒSW = 500 kHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 50. Efficiency vs ILED
LM3533 30135755.gif
L = 4.7 µH VIN = 3.6 V ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 52. Efficiency vs ILED
LM3533 30135748_nosc68.gif
L = 22 µH 20 mA/String ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 39. Efficiency vs VIN, Dual String
LM3533 30135750_nosc68.gif
L = 22 µH 20 mA/String ƒSW = 1 MHz
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 41. Efficiency vs VIN, Single String
LM3533 30135752_nosc68.gif
L = 10 µH 20 mA/String ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 43. Efficiency vs VIN, Dual String
LM3533 30135754_nosc68.gif
L = 10 µH 20 mA/String ƒSW = 1 MHz
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 45. Efficiency vs VIN, Single String
LM3533 30135746_nosc68.gif
L = 4.7 µH 20 mA/String
Top To Bottom: 1×4, 1×5, 1×6, 1×7, 1×8, 1×9, 1×10 (LEDs)
Figure 47. Efficiency vs VIN, Single String
LM3533 30135759.gif
L = 22 µH VIN = 3.6 V ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 49. Efficiency vs ILED
LM3533 30135757.gif
L = 10 µH VIN = 3.6 V ƒSW = 1 MHz
Top To Bottom: 2×4, 2×5, 2×6, 2×7, 2×8, 2×9, 2×10 (LEDs)
Figure 51. Efficiency vs ILED