SLVS847A November   2008  – December 2016 TPS54917

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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 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  Undervoltage Lockout (UVLO)
      2. 8.3.2  Slow Start or Enable (SS/ENA)
      3. 8.3.3  VBIAS Regulator (VBIAS)
      4. 8.3.4  Voltage Reference
      5. 8.3.5  Oscillator and PWM Ramp
      6. 8.3.6  Error Amplifier
      7. 8.3.7  PWM Control
      8. 8.3.8  Dead-Time Control and MOSFET Drivers
      9. 8.3.9  Overcurrent Protection
      10. 8.3.10 Thermal Shutdown
      11. 8.3.11 Power Good (PWRGD)
    4. 8.4 Device Functional Modes
      1. 8.4.1 PWM Operation
      2. 8.4.2 Standby Operation
  9. 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 Component Selection
        2. 9.2.2.2 Input Filter
        3. 9.2.2.3 Feedback Circuit
        4. 9.2.2.4 Operating Frequency
        5. 9.2.2.5 Output Filter
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Estimated Circuit Area
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Developmental Support
    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

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

TPS54917 is a synchronous buck converter. It can convert an input voltage of 3 V to 4 V to a lower voltage. Maximum output current is 9 A.

9.2 Typical Application

Figure 10 shows the schematic diagram for a typical TPS54917 application. The TPS54917 (U1) can provide up to 9 A of output current at a nominal output voltage of 1.8 V. For proper thermal performance, the exposed thermal PowerPAD underneath the integrated circuit (TPS54917) package must be soldered to the printed-circuit board.

TPS54917 app_cir2_lvs847.gif
Analog and power grounds are tied at the pad under the package of the IC
Figure 10. Application Circuit

9.2.1 Design Requirements

Table 2 lists the design specifications for this application example.

Table 2. Application Circuit Specifications

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
INPUT CHARACTERSTICS
VIN Input voltage 3 3.3 4 V
OUTPUT CHARACTERSTICS
VOUT Output voltage 1 VIN = Nom, IOUT = Nom 1.8 V
IOUT 0 9
TRANSIENT RESPONSE
ΔVOUT Change from load transient ΔIOUT = 4.5 A 50 mV
Settling time to 1% of VOUT 0.5 ms
SYSTEMS CHARACTERSTICS
fSW Switching frequency 1600 kHz

9.2.2 Detailed Design Procedure

9.2.2.1 Component Selection

The values for the components used in this design example were selected for best load transient response and small PCB area. Additional design information is available at www.ti.com.

9.2.2.2 Input Filter

The input voltage is a nominal 3.3 VDC. The input filter capacitors (C1 and C2) are 10-µF ceramic capacitors (MuRata). C12 is a 0.01-µF ceramic capacitor that provides high-frequency decoupling of the TPS54917 from the input supply. C1, C2, and C12 must be placed as close as possible to the device. Input ripple current is shared among C1, C2, and C12.

9.2.2.3 Feedback Circuit

The values for these components are selected to provide fast transient response times.

The resistor divider network of R1 and R2 sets the output voltage for the circuit at 1.8 V. R1 along with R6, R7, C5, C7, and C10 forms the loop compensation network for the circuit. For this design, a Type-3 topology is used. The feedback loop is compensated so that the unity gain frequency is approximately 40 kHz.

9.2.2.4 Operating Frequency

In the application circuit, RT is grounded through a 27.4-kΩ resistor to select the operating frequency of 1.6 MHz. To set a different frequency, place a 27-kΩ to 180-kΩ resistor between RT (pin 29) and analog ground or leave RT floating to select the default of 350 kHz. The switching frequency in MHz can be approximated using Equation 4.

Equation 4. TPS54917 q_r_lvs847.gif

9.2.2.5 Output Filter

The output filter is composed of a 0.35-µH inductor and 2 × 100-µF capacitors. The inductor is a dual-coil type (Coilcraft SLC7530-820ML) with the coils wired in series. The capacitors used are 100-µF, 6.3-V ceramic types with X5R dielectric.

9.2.3 Application Curves

TPS54917 amb_lvs847.gif Figure 11. Efficiency vs Output Current
TPS54917 reg3_lvs847.gif
Figure 13. Line Regulation vs Input Voltage
TPS54917 ripp_lvs847.gif Figure 15. Output Ripple Voltage
TPS54917 slow2_lvs847.gif Figure 17. Slow-Start Timing
TPS54917 close_loop_lvs847.gif Figure 19. Closed-Loop Response
TPS54917 load2_lvs847.gif Figure 12. Load Regulation vs Output Current
TPS54917 amb2_lvs847.gif
Safe operating area is applicable to the test board conditions listed in Thermal Information.
Figure 14. Ambient Temperature vs Load Current
TPS54917 res4_lvs847.gif Figure 16. Transient Response
TPS54917 inripp_lvs847.gif Figure 18. Input Ripple