SNOSB43C September   2011  – November 2016 LM3560

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 Specifications (SCL, SDA)
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Power Amplifier Synchronization (Tx1)
        1. 7.3.1.1 TX1 Shutdown
      2. 7.3.2 Independent LED Control
      3. 7.3.3 Hardware Torch
      4. 7.3.4 Fault Protections
        1. 7.3.4.1 Overvoltage Protection
        2. 7.3.4.2 Current Limit
        3. 7.3.4.3 Flash Timeout
        4. 7.3.4.4 Indicator LED/Thermistor (LED1/NTC)
          1. 7.3.4.4.1 Message Indicator Current Source (LEDI/NTC)
            1. 7.3.4.4.1.1 Message Indicator Example 1 (Single Pulse With Dead Time):
            2. 7.3.4.4.1.2 Message Indicator Example 2 (Multiple Pulses With Dead Time):
          2. 7.3.4.4.2 Updating The Message Indicator
      5. 7.3.5 Input Voltage Monitor
        1. 7.3.5.1 Input Voltage Flash Monitor (Flash Current Rising)
      6. 7.3.6 Last Flash Register
      7. 7.3.7 LED Voltage Monitor
      8. 7.3.8 ADC Delay
      9. 7.3.9 Flags Register and Fault Indicators
        1. 7.3.9.1 Flash Timeout
        2. 7.3.9.2 Thermal Shutdown
        3. 7.3.9.3 LED Fault
        4. 7.3.9.4 TX1 and TX2 Interrupt Flags
        5. 7.3.9.5 LED Thermal Fault (NTC Flag)
        6. 7.3.9.6 VIN Flash Monitor Fault
        7. 7.3.9.7 VIN Monitor Fault
    4. 7.4 Device Functional Modes
      1. 7.4.1  Start-Up (Enabling the Device)
      2. 7.4.2  Pass Mode
      3. 7.4.3  Flash Mode
      4. 7.4.4  Torch Mode
      5. 7.4.5  Privacy Indicator Mode
      6. 7.4.6  GPIO1 Mode
      7. 7.4.7  TX2/INT/GPIO2
      8. 7.4.8  TX2 Mode
        1. 7.4.8.1 TX2 Shutdown
      9. 7.4.9  GPIO2 Mode
      10. 7.4.10 Interrupt Output (INT Mode)
      11. 7.4.11 NTC Mode
      12. 7.4.12 Alternate External Torch (AET) Mode
      13. 7.4.13 Automatic Conversion Mode
      14. 7.4.14 Manual Conversion Mode
    5. 7.5 I2C-Compatible Interface
      1. 7.5.1 START and STOP Conditions
      2. 7.5.2 I2C-Compatible Chip Address
      3. 7.5.3 Transferring Data
    6. 7.6 Register Descriptions
      1. 7.6.1  Enable Register (Address 0x10)
      2. 7.6.2  Privacy Register (Address 0x11)
      3. 7.6.3  Indicator Register (Address 0x12)
      4. 7.6.4  Indicator Blinking Register (Address 0x13)
      5. 7.6.5  Privacy PWM Period Register (Address 0x14)
      6. 7.6.6  GPIO Register (Address 0x20)
      7. 7.6.7  LED Forward Voltage ADC (VLED Monitor Register, Address 0x30)
      8. 7.6.8  ADC Delay Register (Address 0x31)
      9. 7.6.9  VIN Monitor Register (Address 0x80)
      10. 7.6.10 Last Flash Register (Address 0x81)
      11. 7.6.11 Torch Brightness Register Descriptions (Address 0xA0)
      12. 7.6.12 Flash Brightness Register (Address 0xB0)
      13. 7.6.13 Flash Duration Register (Address 0xC0)
      14. 7.6.14 Flags Register (Address 0xD0)
      15. 7.6.15 Configuration Register 1 (Address 0xE0)
      16. 7.6.16 Configuration Register 2 (Address 0xF0)
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 LM3560 Typical Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Output Capacitor Selection
          2. 8.2.1.2.2 Input Capacitor Selection
          3. 8.2.1.2.3 Inductor Selection
      2. 8.2.2 NTC Thermistor Application
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Recommendations
    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 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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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 LM3560 is a synchronous boost flash driver with dual 1000-mA high-side current sources. The 2-MHz DC-DC boost regulator allows for the use of small external components. The device operates from a typical input voltage from 2.5 V to 5.5 V and an ambient temperature range of –40°C to +85°C.

8.2 Typical Application

8.2.1 LM3560 Typical Application

LM3560 30102801.gif Figure 41. LM3560 Typical Application

8.2.1.1 Design Requirements

For typical synchronous boost flash driver applications, use the parameters listed in Table 19.

Table 19. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Minimum input voltage 2.5 V
Minimum output voltage 1.8 V
Maximum output current 5 V
Maximum output current 1.8 A
Switching frequency 2 MHz

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Output Capacitor Selection

The LM3560 is designed to operate with at least a 10-µF ceramic output capacitor. When the boost converter is running the output capacitor supplies the load current during the boost converters on-time. When the NMOS switch turns off the inductor energy is discharged through the internal PMOS switch, supplying power to the load and restoring charge to the output capacitor. This causes a sag in the output voltage during the NFET on-time and a rise in the output voltage during the NFET off-time. Therefore chose the output capacitor to limit the output ripple to an acceptable level depending on load current and input/output voltage differentials and also to ensure the converter remains stable.

For proper operation the output capacitor must be at least a 10-µF ceramic. Larger capacitors such as a 22 µF or multiple capacitors in parallel can be used if lower output voltage ripple is desired. To estimate the output voltage ripple considering the ripple due to capacitor discharge (ΔVQ) and the ripple due to the equivalent series resistance (ESR) (ΔVESR) of the capacitor use Equation 1 and Equation 2:

For continuous conduction mode, the output voltage ripple due to the capacitor discharge is:

Equation 1. LM3560 30113827.gif

The output voltage ripple due to the output capacitors ESR is found by:

Equation 2. LM3560 30113828.gif

In ceramic capacitors the ESR is very low so a close approximation is to assume that 80% of the output voltage ripple is due to capacitor discharge and 20% from ESR. Table 20 lists different manufacturers for various output capacitors and their case sizes suitable for use with the LM3560.

8.2.1.2.2 Input Capacitor Selection

Choosing the correct size and type of input capacitor helps minimize the input voltage ripple caused by the switching of the LM3560’s boost converter, and reduces noise on the boost converters input terminal that can feed through and disrupt internal analog signals. In Figure 41 a 10-µF ceramic input capacitor works well. It is important to place the input capacitor as close as possible to the input (IN) pins of the LM3560 device. This reduces the series resistance and inductance that can inject noise into the device due to the input switching currents. Table 20 lists various input capacitors that are recommended for use with the LM3560.

Table 20. Recommended Input/Output Capacitors (X5r Dielectric)

MANUFACTURER PART NUMBER VALUE CASE SIZE VOLTAGE RATING
TDK Corporation C1608JB0J106M 10 µF 0603 (1.6 mm × 0.8mm × 0.8 mm) 6.3 V
TDK Corporation C2012JB1A106M 10 µF 0805 (2 mm ×1.25 mm × 1.25 mm) 10 V
Murata GRM21BR61A106KE19 10 µF 0805 (2 mm × 1.25 mm × 1.25 mm) 10 V

8.2.1.2.3 Inductor Selection

The LM3560 is designed to use a 1-µH or 2.2-µH inductor. Table 21 lists various inductors and their manufacturers that can work well with the LM3560. When the device is boosting (VOUT > VIN) the inductor is typically the largest area of efficiency loss in the circuit. Therefore, choosing an inductor with the lowest possible series resistance is important. Additionally, the saturation rating of the inductor must be greater than the maximum operating peak current of the LM3560. This prevents excess efficiency loss that can occur with inductors that operate in saturation. For proper inductor operation and circuit performance, ensure that the inductor saturation and the peak current limit setting of the LM3560 are greater than IPEAK in the following calculation:

Equation 3. LM3560 30113829.gif

where

Table 21. Recommended Inductors

MANUFACTURER L PART NUMBER DIMENSIONS (L × W × H) ISAT RDC
TOKO 2.2 µH FDSD0312-H-2R02M 3 mm × 3.2 mm × 1.2 mm 2.3 A 105 mΩ
TOKO 1 µH FDSD0312-H-1R0M 3 mm × 3.2 mm × 1.2 mm 3.4 A 43 mΩ
TDK 1 µH VLS252012T-1R0N 2 mm × 2.5 mm × 1.2 mm 2.45 A 73 mΩ
TDK 1 µH VLS4012ET-1R0N 4 mm × 4 mm × 1.2 mm 2.8 A 50 mΩ

8.2.2 NTC Thermistor Application

Programming bit [4] of Configuration register 1 with a 1 selects NTC mode and makes the LEDI/NTC pin a comparator input for flash LED thermal sensing. Figure 42 shows the LM3560 using the NTC thermistor circuit. The thermal sensor resistor divider is composed of R3 and R(T), where R(T) is the negative temperature coefficient thermistor, VBIAS is the bias voltage for the resistive divider, and R3 is used to linearize the response of the NTC around the NTC comparators trip point. CBYP is used to filter noise at the NTC input.

LM3560 30113836.gif Figure 42. Typical Application Circuit With Thermistor

In designing the NTC circuit, values for VBIAS, R(T) and R3, must be chosen. To begin with, NTC thermistors have a non-linear relationship between temperature and resistance:

Equation 4. LM3560 30113831.gif

where

  • β is given in the thermistor data sheet
  • R25C is the value of the thermistor at 25°C

R3 is chosen so that the temperature to resistance relationship becomes more linear and can be found by solving for R3 in the R(T) and R3 resistive divider:

Equation 5. LM3560 30113832.gif

where

  • R(T)TRIP is the thermistor's value at the temperature trip point
  • VTRIP = 1V (typical)

As an example, with VBIAS = 2.5 V and a thermistor whose nominal value at 25°C is 100 kΩ and a β = 4500 K, the trip point is chosen to be 93°C. The value of R(T) at 93°C is:

Equation 6. LM3560 q_rt_nosb43.gif

Figure 43 shows the linearity of the thermistor resistive divider of the previous example.

LM3560 30113834.gif Figure 43. Thermistor Resistive Divider Response vs Temperature

8.2.3 Application Curves

LM3560 301138100.gif
Highest 4 Flash Brightness Codes
Figure 44. LED Efficiency vs VIN, LED1 and LED2
LM3560 301138103.gif
Lower Middle 4 Flash Brightness Codes
Figure 46. LED Efficiency vs VIN, LED1 and LED2
LM3560 301138102.gif
Upper Middle 4 Flash Brightness Codes
Figure 45. LED Efficiency vs VIN, LED1 and LED2
LM3560 301138104.gif
Lowest 4 Flash Brightness Codes
Figure 47. LED Efficiency vs VIN, LED1 and LED2