SLUSBZ6A April   2016  – August 2016 TPS92515 , TPS92515-Q1 , TPS92515HV , TPS92515HV-Q1


  1. Features
  2. Applications
  3. Description
    1.     Simplified Buck LED Driver Application
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1. Table 1. Pin 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 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  General Operation
      2. 8.3.2  Current Sense Comparator
      3. 8.3.3  OFF Timer
      4. 8.3.4  OFF-Timer, Shunt FET Dimming or Shunted Output Condition
      5. 8.3.5  Internal N-channel MOSFET
        1. Drop-Out
      6. 8.3.6  VCC Internal Regulator and Undervoltage Lockout (UVLO)
      7. 8.3.7  Analog Adjust Input
        1. IADJ Pin Clamp
        2. IADJ Pin Clamp Characteristic
        3. Analog Adjust (IADJ Pin) Control Methods
        4. IADJ Control Method Notes
      8. 8.3.8  Thermal Protection
        1. Maximum Output Current and Junction Temperature
      9. 8.3.9  Junction Temperature Relative Estimation
      10. 8.3.10 BOOT and BOOT UVLO
        1. Start-Up, BOOT-UVLO and Pre-Charged Condition
      11. 8.3.11 PWM (UVLO and Enable)
        1. Using PWM for UVLO (Undervoltage Lockout) Protection
          1. UVLO Programming Resistors
        2. Using PWM for Digitally Controlled Enable
        3. UVLO: VIN, VCC and BOOT UVLO
        4. Analog and PWM Dimming - Normalized Results and Comparison
    4. 8.4 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 General Design Procedure
        1. Calculating Duty Cycle
        2. Calculate OFF-Time Estimate
        3. Calculate OFF-Time Resistor ROFF
        4. Calculate the Minimum Inductance Value
        5. Calculate the Sense Resistance
        6. Calculate Input Capacitance
        7. Calculate Output Capacitance
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
        1. Calculating Duty Cycle
        2. Calculate OFF-Time Estimate
        3. Calculate OFF-Time Resistor ROFF
        4. Calculate the Inductance Value
        5. Calculate the Sense Resistance
        6. Calculate Input Capacitance
        7. Verify Peak Current for Inductor Selection
        8. Calculate Output Capacitance
        9. Calculate UVLO Resistance Values
      4. 9.2.4 Application Curves
    3. 9.3 Dos and Don'ts
  10. 10Power Supply Recommendations
    1. 10.1 Input Source Direct from Battery
    2. 10.2 Input Source from a Boost Stage
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
        1. Related Links
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Maximum Output Current and Junction Temperature

As with all power converter controllers and regulators, practical limits to specification maximums must be considered for each application. For example, it is not possible to operate the TPS92515 with a switching frequency of 1 MHz, output current of 2 A, at an ambient temperature of 125°C and stay within operating limits. Conversion factors and environment must be considered. This section describes two conversion scenarios with different operating conditions that would result in approximately the same junction temperature. In each case all of the power loss factors combine to develop the device junction temperature.

Figure 24 describes a design with half the output current and a lower switching frequency compared to that shown in Figure 23. However, the design shown in Figure 24 has a higher ambient temperature, higher VIN and an additional external VCC load, resulting in similar junction temperature. Table 3 lists trade-offs and impact on temperature. In general, applications requiring high current (2 A) or a high switching frequency (> 1 MHz) provide reduced maximum ambient temperature levels.

TPS92515 TPS92515-Q1 TPS92515HV TPS92515HV-Q1 power_balance.gif
ILED = 1 A VIN = 14 V
fSW = 500 kHz TA = 85°C
Figure 23. Power Balanced
TPS92515 TPS92515-Q1 TPS92515HV TPS92515HV-Q1 power_notbalance.gif
ILED = 500 mA TA = 125°C
fSW = 300 kHz External VCC load = 500 µA
VIN = 60 V
Figure 24. Power Unbalanced

Table 3. Device Junction Temperature Factors

TA Ambient temperature An increase in the ambient temperatre will increase the junction temperature by the same amount.
VIN Input voltage A higher input voltage results in more power developed across the internal regulator resulting in higher internal losses. A higher voltage often yields a larger step-down conversion and lower efficiency.
ILED LED current A higher LED output current results in higher power (I2R) losses in current carrying elements like the internal MOSFET.
IVCC(ext) External VCC current Current used to supply additional loads external to the TPS92515 device draw from the internal regulator. More external current results in an increased junction temperature. When an external source supplies the BOOT current internal power dissipation decreases.
fSW Switching frequency Each time the internal FET is turned ON and OFF, current must flow from VCC to the gate driver. The current drawn by a switching gate approximately equals the gate charge times the switching frequency. Power loss associated with the switching edge transitions also increase with frequency.
η Efficiency Switching conversions requiring difficult conversions (small duty cycles) have higher overall losses. These losses increase the overall temperature of the application and the device temperature.