SLUSC70D March   2016  – July 2017 TPS548D22

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Application
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 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 40-A FET
      2. 7.3.2 On-Resistance
      3. 7.3.3 Package Size, Efficiency and Thermal Performance
      4. 7.3.4 Soft-Start Operation
      5. 7.3.5 VDD Supply Undervoltage Lockout (UVLO) Protection
      6. 7.3.6 EN_UVLO Pin Functionality
      7. 7.3.7 Fault Protections
        1. 7.3.7.1 Current Limit (ILIM) Functionality
        2. 7.3.7.2 VDD Undervoltage Lockout (UVLO)
        3. 7.3.7.3 Overvoltage Protection (OVP) and Undervoltage Protection (UVP)
        4. 7.3.7.4 Out-of-Bounds Operation
        5. 7.3.7.5 Overtemperature Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 DCAP3 Control Topology
      2. 7.4.2 DCAP Control Topology
    5. 7.5 Programming
      1. 7.5.1 Programmable Pin-Strap Settings
        1. 7.5.1.1 Frequency Selection (FSEL) Pin
        2. 7.5.1.2 VSEL Pin
        3. 7.5.1.3 DCAP3 Control and Mode Selection
          1. 7.5.1.3.1 Application Workaround to Support 4-ms and 8-ms SS Settings
      2. 7.5.2 Programmable Analog Configurations
        1. 7.5.2.1 RSP/RSN Remote Sensing Functionality
          1. 7.5.2.1.1 Output Differential Remote Sensing Amplifier
        2. 7.5.2.2 Power Good (PGOOD Pin) Functionality
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 TPS548D22 1.5-V to 16-V Input, 1-V Output, 40-A Converter
      2. 8.2.2 Design Requirements
      3. 8.2.3 Design Procedure
        1. 8.2.3.1  Switching Frequency Selection
        2. 8.2.3.2  Inductor Selection
        3. 8.2.3.3  Output Capacitor Selection
          1. 8.2.3.3.1 Minimum Output Capacitance to Ensure Stability
          2. 8.2.3.3.2 Response to a Load Transient
          3. 8.2.3.3.3 Output Voltage Ripple
        4. 8.2.3.4  Input Capacitor Selection
        5. 8.2.3.5  Bootstrap Capacitor Selection
        6. 8.2.3.6  BP Pin
        7. 8.2.3.7  R-C Snubber and VIN Pin High-Frequency Bypass
        8. 8.2.3.8  Optimize Reference Voltage (VSEL)
        9. 8.2.3.9  MODE Pin Selection
        10. 8.2.3.10 Overcurrent Limit Design.
      4. 8.2.4 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 Mounting and Thermal Profile Recommendation
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.3.1 Switching Frequency Selection

Select a switching frequency for the regulator. There is a trade off between higher and lower switching frequencies. Higher switching frequencies may produce smaller a solution size using lower valued inductors and smaller output capacitors compared to a power supply that switches at a lower frequency. However, the higher switching frequency causes extra switching losses, which decrease efficiency and impact thermal performance. In this design, a moderate switching frequency of 650 kHz achieves both a small solution size and a high-efficiency operation with the frequency selected.

Select one of four switching frequencies and FSEL resistor values from Table 6. The recommended high-side RFSEL value is 100 kΩ (1%). Choose a low-side resistor value from Table 6 based on the choice of switching frequency. For each switching frequency selection, there are multiple values of RFSEL(LS) to choose from. In order to select the correct value, additional considerations (internal ramp compensation and light load operation) other than switching frequency need to be included.

Table 6. FSEL Pin Selection

SWITCHING FREQUENCY
fSW (kHz)		 FSEL VOLTAGE
VFSEL (V)		 HIGH-SIDE RESISTOR
RFSEL(HS)
(kΩ) 1% or better		 LOW-SIDE RESISTOR
RFSEL(LS) (kΩ)
1% or better
MAXIMUM MINIMUM
1050 2.93 1.465 100 Open
187
165
147
133
121
110
100
875 1.396 0.869 100 90.9
82.5
75
68.1
60.4
53.6
47.5
42.2
650 0.798 0.366 100 37.4
33.2
29.4
25.5
22.1
19.1
16.5
14.3
425 0.317 0 100 12.1
10
7.87
6.19
4.64
3.16
1.78
0

There is some limited freedom to choose FSEL resistors that have other than the recommended values. The criteria is to ensure that for particular selection of switching frequency, the FSEL voltage is within the maximum and minimum FSEL voltage levels listed in Table 6. Use Equation 2 to calculate the FSEL voltage. Select FSEL resistors that include tolerances of 1% or better.

Equation 2. TPS548D22 eq_vfsel_slusc70.gif

where

  • VBP(det) is the voltage used by the device to program the level of valid FSEL pin voltage during initial device start-up (2.9 V typ)

In addition to serving the frequency select purpose, the FSEL pin can also be used to program internal ramp compensation (DCAP3) and light-load conduction mode. When DCAP3 mode is selected (see section 8.2.3.9), internal ramp compensation is used for stabilizing the converter design. The internal ramp compensation is a function of the switching frequency (fSW) and the duty cycle range (the output voltage-to-input voltage ratio). Table 7 summarizes the ramp choices using these functions.

Table 7. Switching Frequency Selection

SWITCHING FREQUENCY
SETTING
(fSW) (kHz)		 RAMP
SELECT
OPTION		 TIME
CONSTANT
t (µs)		 VOUT RANGE
(FIXED VIN = 12 V)		 DUTY CYCLE RANGE
(VOUT/VIN) (%)
MIN MAX MIN MAX
425 R/2 9 0.6 0.9 5 7.5
R × 1 16.8 0.9 1.5 7.5 12.5
R × 2 32.3 1.5 2.5 12.5 21
R × 3 55.6 2.5 5.5 >21
650 R/2 7 0.6 0.9 5 7.5
R × 1 13.5 0.9 1.5 7.5 12.5
R × 2 25.9 1.5 2.5 12.5 21
R × 3 44.5 2.5 5.5 >21
875 R/2 5.6 0.6 0.9 5 7.5
R × 1 10.4 0.9 1.5 7.5 12.5
R × 2 20 1.5 2.5 12.5 21
R × 3 34.4 2.5 5.5 >21
1050 R/2 3.8 0.6 0.9 5 7.5
R × 1 7.1 0.9 1.5 7.5 12.5
R × 2 13.6 1.5 2.5 12.5 21
R × 3 23.3 2.5 5.5 >21

The FSEL pin programs the light-load selection. TPS548D22 device supports either SKIP mode or FCCM operations. For optimized light-load efficiency, it is recommended to program the device to operate in SKIP mode. For better load regulation from no load to full load, it is recommended to program the device to operate in FCCM mode.

RFSEL(LS) can be determined after determining the switching frequency, ramp and light-load operation. Table 2 lists the full range of choices.