SLUS909B May   2009  – August 2014 TPS53126

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematics
  5. 5 Revision History
  6. 6 Pin Configurations and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 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  PWM Operation
      2. 8.3.2  Drivers
      3. 8.3.3  PWM Frequency And Adaptive On-time Control
      4. 8.3.4  5 Volt Regulator
      5. 8.3.5  Soft Start
      6. 8.3.6  Pre-Bias Support
      7. 8.3.7  Switching Frequency Selection
      8. 8.3.8  Output Discharge Control
      9. 8.3.9  Overcurrent Limit
      10. 8.3.10 Over/under Voltage Protection
      11. 8.3.11 UVLO Protection
      12. 8.3.12 Thermal Shutdown
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 350 kHz Operation Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Choose Inductor
        2. 9.2.2.2 Choose Output Capacitor
        3. 9.2.2.3 Choose Input Capacitor
        4. 9.2.2.4 Choose Bootstrap Capacitor
        5. 9.2.2.5 Choose VREG5 and V5FILT Capacitors
        6. 9.2.2.6 Choose Output Voltage Set Point Resistors
        7. 9.2.2.7 Choose Over Current Limit Set Point Resistors
      3. 9.2.3 350 kHz Application Curves
    3. 9.3 700 Khz Operation Application
      1. 9.3.1 Design Parameters
      2. 9.3.2 Detailed Design Procedure
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGE|24
  • PW|24
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Application and Implementation

9.1 Application Information

9.2 350 kHz Operation Application

The schematic of Figure 14 shows a typical 350 kHz application schematic. The 350 kHz switching frequency is selected by connecting TEST2 to the GND pin. The input voltage is 4.5 V to 24 V and the output voltage is 1.8 V for VO1 and 1.05 V for VO2.

typ_app_350_lus909.gifFigure 14. Typical Application Circuit at 350kHz Switching Frequency Selection (TEST2 Pin = GND)

9.2.1 Design Requirements

Table 1. Design Parameters

PARAMETERS CHANNEL 1 CHANNEL 2
Input voltage 4.5 V to 24 V 4.5 V to 24 V
Output voltage 1.8 V 1.05 V
Output Current 4 A 4 A
Switching Frequency 350 kHz 350 kHz

9.2.2 Detailed Design Procedure

9.2.2.1 Choose Inductor

The inductance value is selected to provide approximately 30% peak to peak ripple current at maximum load. Larger ripple current increases output ripple voltage, improve S/N ratio and contribute to stable operation. Equation 3 can be used to calculate L1.

Equation 3. eq3_l1_lus909.gif

The inductors current ratings needs to support both the RMS (thermal) current and the Peak (saturation) current. The RMS and peak inductor current can be estimated as follows:

Equation 4. eq4_il1_lus909.gif
Equation 5. eq5_il1_pk_lus909.gif
Equation 6. eq6_il1rms_lus909.gif

Note: The calculation above shall serve as a general reference. To further improve transient response, the output inductance could be reduced further. This needs to be considered along with the selection of the output capacitor.

9.2.2.2 Choose Output Capacitor

The capacitor value and ESR determines the amount of output voltage ripple and load transient response. Recommend to use ceramic output capacitor.

Equation 7. eq7_c1_lus909.gif
Equation 8. eq8_c1a_lus909.gif

Where:

Equation 9. eq9_k_lus909.gif
Equation 10. eq10_c1b_lus909.gif

Select the capacitance value greater than the largest value calculated from Equation 7, Equation 8 and Equation 10. The capacitance for C1 should be greater than 66 μF.

Where:

ΔVos = the allowable amount of overshoot voltage in load transition

ΔVus = the allowable amount of undershoot voltage in load transition

Tmin(off) = Min-off time

9.2.2.3 Choose Input Capacitor

The TPS53126 requires an input decoupling capacitor and a bulk capacitor is needed depending on the application. A minimum 10-μF high-quality ceramic capacitor is recommended for the input capacitor. The capacitor voltage rating needs to be greater than the maximum input voltage.

9.2.2.4 Choose Bootstrap Capacitor

The TPS53126 requires a bootstrap capacitor from SWx to VBSTx to provide the floating supply for the high-side drivers. A minimum 0.1-μF high-quality ceramic capacitor is recommended. The voltage rating should be greater than 6 V.

9.2.2.5 Choose VREG5 and V5FILT Capacitors

The TPS53126 requires both the VREG5 regulator and V5FILT input are bypassed. A minimum 4.7-μF high-quality ceramic capacitor must be connected between the VREG5 and GND for proper operation. A minimum 1.0-μF high-quality ceramic capacitor must be connected between the V5FILT and GND for proper operation. Both of these capacitors’ voltage ratings should be greater than 6 V.

9.2.2.6 Choose Output Voltage Set Point Resistors

The output voltage is set with a resistor divider from output voltage node to the VFBx pin. It is recommended to use 1% tolerance or better resisters. Select R2 between 10 kΩ and 100 kΩ and use Equation 11 and Equation 12 to calculate R1.

Equation 11. eq11_r1a_lus909.gif
Equation 12. eq12_r1b_lus909.gif

Where:

VFB1(ripple) = Ripple Voltage at VFB1

9.2.2.7 Choose Over Current Limit Set Point Resistors

Equation 13. eq13_vtrip_lus909.gif
Equation 14. eq14_rtrip_lus909.gif

Where:

RDS(on) = Low Side FET on-resistance
Itrip = TRIP pin source current （= 10 μA）
IOCL = Over current limit

9.2.3 350 kHz Application Curves

Application curves Figure 15, Figure 16, Figure 17, Figure 18, Figure 23 and Figure 24 apply to both the circuits of 350 kHz Operation Application and 700 Khz Operation Application.

g014_lus909.gif
IO1 = 3 A
Figure 15. SWITCHING FREQUENCY vs INPUT VOLTAGE (CH1)
g016_lus909.gif
VIN = 12 V
Figure 17. OUTPUT VOLTAGE vs OUTPUT CURRENT (CH1)
g018_lus909.gif
CH1, TEST2 = GND
Figure 19. 1.8V LOAD TRANSIENT RESPONSE
g022_lus909.gif
Figure 21. 1.8V START-UP WAVEFORMS
g026_lus909.gif
IO = 3 A
Figure 23. 1.8V OUTPUT VOLTAGE vs INPUT VOLTAGE
g028_lus909.gif
Figure 25. 1.8V OUTPUT RIPPLE VOLTAGE
g015_lus909.gif
IO2 = 3 A
Figure 16. SWITCHING FREQUENCY vs INPUT VOLTAGE (CH2)
g017_lus909.gif
VIN = 12 V
Figure 18. OUTPUT VOLTAGE vs OUTPUT CURRENT (CH2)
g020_lus909.gif
CH2, TEST2 = GND
Figure 20. 1.05V LOAD TRANSIENT RESPONSE
g024_lus909.gif
VIN = 12 V
Figure 22. 1.8V EFFICIENCY vs OUTPUT CURRENT (CH1)
g027_lus909.gif
IO = 3 A
Figure 24. 1.05V OUTPUT VOLTAGE vs INPUT VOLTAGE

9.3 700 Khz Operation Application

The schematic of Figure 26 shows a typical 700 kHz application schematic. The 700 kHz switching frequency is selected by connecting TEST2 to the V5FILT pin. The input voltage is 4.5 V to 24 V and the output voltage is 1.8 V for VO1 and 1.05 V for VO2.

typ_app_700_lus909.gifFigure 26. Typical Application Circuit at 700 kHz Switching frequency Selection (TEST2 Pin = V5FILT)

9.3.1 Design Parameters

PARAMETERS CHANNEL 1 CHANNEL 2
Input voltage 4.5 to 24 V 4.5 to 24 V
Output voltage 1.8 V 1.05 V
Output current 4 A 4 A
Switching Frequency 700 kHz 700 kHz

9.3.2 Detailed Design Procedure

For the Detailed Design Procedure, refer to Detailed Design Procedure.

700 kHz Application Curves

Application curves Figure 15, Figure 16, Figure 17, Figure 18, Figure 23 and Figure 24 apply to both the circuits of 350 kHz Operation Application and 700 Khz Operation Application.

g019_lus909.gif
CH1, TEST2 = V5FILT
Figure 27. 1.8V LOAD TRANSIENT RESPONSE
g023_lus909.gif
Figure 29. 1.05V START-UP WAVEFORMS
g029_lus909.gif
Figure 31. 1.05V OUTPUT RIPPLE VOLTAGE
g021_lus909.gif
CH2, TEST2 = V5FILT
Figure 28. 1.05V LOAD TRANSIENT RESPONSE
g025_lus909.gif
VIN = 12 V
Figure 30. 1.05V EFFICIENCY vs OUTPUT CURRENT (CH2)