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

8.2.3.10 Overcurrent Limit Design.

The TPS548D22 device uses the ILIM pin to set the OCP level. Connect the ILIM pin to GND through the voltage setting resistor, RILIM. In order to provide both good accuracy and cost effective solution, this device supports temperature compensated MOSFET on-resistance (RDS(on)) sensing. Also, this device performs both positive and negative inductor current limiting with the same magnitudes. Positive current limit is normally used to protect the inductor from saturation therefore causing damage to the high-side and low-side FETs. Negative current limit is used to protect the low-side FET during OVP discharge.

The inductor current is monitored by the voltage between PGND pin and SW pin during the OFF time. The ILIM pin has 3000 ppm/°C temperature slope to compensate the temperature dependency of the on-resistance. The PGND pin is used as the positive current sensing node.

TPS548D22 has cycle-by-cycle over-current limiting control. The inductor current is monitored during the OFF state and the controller maintains the OFF state during the period that the inductor current is larger than the overcurrent ILIM level. The voltage on the ILIM pin (VILIM) sets the valley level of the inductor current. The range of value of the RILIM resistor is between 21 kΩ and 237 kΩ. The range of valley OCL is between 6.25 A and 75 A (typical). If the RILIM resistance is outside of the recommended range, OCL accuracy and function cannot be guaranteed. (see Table 8).

Table 8. Closed Loop EVM Measurement of OCP Settings

RILIM
(kΩ)		 OVERCURRENT PROTECTION VALLEY (A)
MIN NOM MAX
237 — 75 —
127 36 40 44
95.3 27 30 33
63.4 18 20 22
32.4 9 10 11
21 — 6.25 —

Use Equation 15 to relate the valley OCL to the RILIM resistance.

Equation 15. TPS548D22 eq_ocl_val_slusc70.gif

where

  • RILIM is in kΩ
  • OCLVALLEY is in A

In this design example, the desired valley OCL is 43 A, the calculated RILIM is 137 kΩ. Use Equation 16 to calculate the DC OCL to be 46 A.

Equation 16. TPS548D22 eq_ocl_dc_slusc70.gif

where

  • RILIM is in kΩ
  • OCLDC is in A

In an overcurrent condition, the current to the load exceeds the inductor current and the output voltage falls. When the output voltage crosses the under-voltage fault threshold for at least 1msec, the behavior of the device depends on the VSEL pin strap setting. If hiccup mode is selected, the device will restart after 16-ms delay (1-ms soft-start option). If the overcurrent condition persists, the OC hiccup behavior repeats. During latch-off mode operation the device shuts down until the EN pin is toggled or VDD pin is power cycled.