SNVS871M July   2012  – June 2020 LP8556

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Simplified Schematic
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Options
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 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  Electrical Characteristics — Boost Converter
    7. 7.7  Electrical Characteristics — LED Driver
    8. 7.8  Electrical Characteristics — PWM Interface
    9. 7.9  Electrical Characteristics — Logic Interface
    10. 7.10 I2C Serial Bus Timing Parameters (SDA, SCL)
    11. 7.11 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Boost Converter
        1. 8.3.1.1 Boost Converter Operation
        2. 8.3.1.2 Setting Boost Switching Frequency
        3. 8.3.1.3 Output Voltage Control
          1. 8.3.1.3.1 Adaptive Control
          2. 8.3.1.3.2 Manual Control
        4. 8.3.1.4 EMI Reduction
      2. 8.3.2 Brightness Control
        1. 8.3.2.1  BRT_MODE = 00
        2. 8.3.2.2  BRT_MODE = 01
        3. 8.3.2.3  BRT_MODE = 10
        4. 8.3.2.4  BRT_MODE = 11
        5. 8.3.2.5  Output Dimming Schemes
          1. 8.3.2.5.1 PWM Control
          2. 8.3.2.5.2 Pure Current Control
          3. 8.3.2.5.3 Adaptive Control
        6. 8.3.2.6  Setting Full-Scale LED Current
        7. 8.3.2.7  Setting PWM Dimming Frequency
        8. 8.3.2.8  Phase Shift PWM Scheme
        9. 8.3.2.9  Slope and Advanced Slope
        10. 8.3.2.10 Dithering
      3. 8.3.3 Fault Detection
        1. 8.3.3.1 LED Fault Detection
          1. 8.3.3.1.1 Open Detect
          2. 8.3.3.1.2 Short Detect
        2. 8.3.3.2 Undervoltage Detection
        3. 8.3.3.3 Overcurrent Protection
        4. 8.3.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Active Mode
    5. 8.5 Programming
      1. 8.5.1 I2C-Compatible Serial Bus Interface
        1. 8.5.1.1 Interface Bus Overview
        2. 8.5.1.2 Data Transactions
        3. 8.5.1.3 Acknowledge Cycle
        4. 8.5.1.4 Acknowledge After Every Byte Rule
        5. 8.5.1.5 Addressing Transfer Formats
        6. 8.5.1.6 Control Register Write Cycle
        7. 8.5.1.7 Control Register Read Cycle
        8. 8.5.1.8 Register Read and Write Detail
    6. 8.6 Register Maps
      1. 8.6.1 Register Bit Explanations
        1. 8.6.1.1 Brightness Control
        2. 8.6.1.2 Device Control
        3. 8.6.1.3 Status
        4. 8.6.1.4 Direct Control
        5. 8.6.1.5 LED String Enable
      2. 8.6.2 EPROM Bit Explanations
        1. 8.6.2.1  LP8556TM (DSBGA) Configurations and Pre-Configured EPROM Settings
        2. 8.6.2.2  LP8556TM (DSBGA) Configurations and Pre-configured EPROM Settings Continued
        3. 8.6.2.3  LP8556SQ (WQFN) Configurations and Pre-configured EPROM Settings
        4. 8.6.2.4  CFG98
        5. 8.6.2.5  CFG9E
        6. 8.6.2.6  CFG0
        7. 8.6.2.7  CFG1
        8. 8.6.2.8  CFG2
        9. 8.6.2.9  CFG3
        10. 8.6.2.10 CFG4
        11. 8.6.2.11 CFG5
        12. 8.6.2.12 CFG6
        13. 8.6.2.13 CFG7
        14. 8.6.2.14 CFG9
        15. 8.6.2.15 CFGA
        16. 8.6.2.16 CFGE
        17. 8.6.2.17 CFGF
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Using LP8556 With I2C Host
        1. 9.1.1.1 Setting Boost Switching and PWM Dimming Frequencies
        2. 9.1.1.2 Setting Full-Scale LED Current
      2. 9.1.2 Using LP8556 With Configuration Resistors and IO Pins
        1. 9.1.2.1 Setting Boost Switching and PWM Dimming Frequencies
        2. 9.1.2.2 Setting Full-Scale LED Current
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Recommended Inductance for the Boost Power Stage
        2. 9.2.2.2 Recommended Capacitances for the Boost and LDO Power Stages
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.2.7 Setting PWM Dimming Frequency

LP8556 PWM dimming frequency can be set by an external resistor, RFSET, or by pre-configuring EPROM Memory (CFG5 register, PWM_FREQ[3:0] bits). Table 4 summarizes setting of the PWM dimming frequency. Note that .

NOTE

The RFSET is shared for setting the boost switching frequency, too. Setting the boost switching frequency and PWM dimming frequency using an external resistor is shown in Table 5.

Table 4. Configuring PWM Dimming Frequency via EPROM

RFSET [kΩ] PWM_FSET_EN PWM_FREQ[3:0] ƒPWM [Hz] (Resolution)
don't care 0 0000 4808 (11-bit)
0001 6010 (10-bit)
0010 7212 (10-bit)
0011 8414 (10-bit)
0100 9616 (10-bit)
0101 12020 (9-bit)
0110 13222 (9-bit)
0111 14424 (9-bit)
1000 15626 (9-bit)
1001 16828 (9-bit)
1010 18030 (9-bit)
1011 19232 ((9-bit)
1100 24040 (8-bit)
1101 28848 (8-bit)
1110 33656 (8-bit)
1111 38464 (8-bit)
See(1) 1 don't care See(1)
(1) See Table 5.

Table 5. Setting Switching and PWM Dimming Frequency With an External Resistor

RFSET [Ω] (Tolerance) ƒSW [kHz] ƒPWM [Hz] (Resolution)
Floating or FSET pin pulled HIGH 1250 9616 (10-bit)
470k - 1M (±5%) 312 2402 (12-bit)
300k, 330k (±5%) 312 4808 (11-bit)
200k (±5%) 312 6010 (10-bit)
147k, 150k, 154k, 158k (±1%) 312 9616 (10-bit)
121k (±1%) 312 12020 (9-bit)
100k (±1%) 312 14424 (9-bit)
86.6k (±1%) 312 16828 (9-bit)
75.0k (±1%) 312 19232 (9-bit)
63.4k (±1%) 625 2402 (12-bit)
52.3k, 53.6k (±1%) 625 4808 (11-bit)
44.2k, 45.3k (±1%) 625 6010 (10-bit)
39.2k (±1%) 625 9616 (10-bit)
34.0k (±1%) 625 12020 (9-bit)
30.1k (±1%) 625 14424 (9-bit)
26.1k (±1%) 625 16828 (9-bit)
23.2k (±1%) 625 19232 (9-bit)
20.5k (±1%) 1250 2402 (12-bit)
18.7k (±1%) 1250 4808 (11-bit)
16.5k (±1%) 1250 6010 (10-bit)
14.7k (±1%) 1250 9616 (10-bit)
13.0k (±1%) 1250 12020 (9-bit)
11.8k (±1%) 1250 14424 (9-bit)
10.7k (±1%) 1250 16828 (9-bit)
9.76k (±1%) 1250 19232 (9-bit)
FSET pin shorted to GND 1250 Same as PWM input