SLVSAA4G June   2010  – February 2018 TPS65251

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin 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  Adjustable Switching Frequency
      2. 8.3.2  Synchronization
      3. 8.3.3  Out-of-Phase Operation
      4. 8.3.4  Delayed Start-Up
      5. 8.3.5  Soft-Start Time
      6. 8.3.6  Adjusting the Output Voltage
      7. 8.3.7  Input Capacitor
      8. 8.3.8  Bootstrap Capacitor
      9. 8.3.9  Error Amplifier
      10. 8.3.10 Loop Compensation
      11. 8.3.11 Slope Compensation
      12. 8.3.12 Powergood
      13. 8.3.13 Current Limit Protection
      14. 8.3.14 Overvoltage Transient Protection
      15. 8.3.15 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Low-Power Mode 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  Loop Compensation Circuit
        2. 9.2.2.2  Selecting the Switching Frequency
        3. 9.2.2.3  Output Inductor Selection
        4. 9.2.2.4  Output Capacitor
        5. 9.2.2.5  Input Capacitor
        6. 9.2.2.6  Soft-Start Capacitor
        7. 9.2.2.7  Bootstrap Capacitor Selection
        8. 9.2.2.8  Adjustable Current Limiting Resistor Selection
        9. 9.2.2.9  Output Voltage and Feedback Resistors Selection
        10. 9.2.2.10 Compensation
        11. 9.2.2.11 3.3-V and 6.5-V LDO Regulators
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Power Dissipation
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

6 Pin Configuration and Functions

RHA Package
40-Pin VQFN
Top View
TPS65251 po_lvsaa4.gif

Pin Functions

PINI/ODESCRIPTION
NAMENO.
RLIM3 1 I Current limit setting for Buck 3. Fit a resistor from this pin to ground to set the peak current limit on the output inductor.
SS3 2 I Soft-start pin for Buck 3. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
COMP3 3 O Compensation for Buck 3. Fit a series RC circuit to this pin to complete the compensation circuit of this converter.
FB3 4 I Feedback input for Buck 3. Connect a divider set to 0.8V from the output of the converter to ground.
SYNC 5 I Synchronous clock input. If there is a sync clock in the system, connect to the pin. When not used connect to GND.
ROSC 6 I Oscillator set. This resistor sets the frequency of internal autonomous clock. If external synchronization is used resistor should be fitted and set to about 70% of external clock frequency.
FB1 7 I Feedback pin for Buck 1. Connect a divider set to 0.8 V from the output of the converter to ground.
COMP1 8 O Compensation pin for Buck 1. Fit a series RC circuit to this pin to complete the compensation circuit of this converter.
SS1 9 I Soft-start pin for Buck 1. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
RLIM1 10 I Current limit setting pin for Buck 1. Fit a resistor from this pin to ground to set the peak current limit on the output inductor.
EN1 11 I Enable pin for Buck 1. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.
BST1 12 I Bootstrap capacitor for Buck 1. Fit a 47-nF ceramic capacitor from this pin to the switching node.
VIN1 13 I Input supply for Buck 1. Fit a 10-µF ceramic capacitor close to this pin.
LX1 14 O Switching node for Buck 1
15
LX2 16 O Switching node for Buck 2
17
VIN2 18 I Input supply for Buck 2. Fit a 10-µF ceramic capacitor close to this pin.
BST2 19 I Bootstrap capacitor for Buck 2. Fit a 47-nF ceramic capacitor from this pin to the switching node.
EN2 20 I Enable pin for Buck 2. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.
RLIM2 21 I Current limit setting for Buck 2. Fit a resistor from this pin to ground to set the peak current limit on the output inductor.
SS2 22 I Soft-start pin for Buck 2. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
COMP2 23 O Compensation pin for Buck 2. Fit a series RC circuit to this pin to complete the compensation circuit of this converter
FB2 24 I Feedback input for Buck 2. Connect a divider set to 0.8 V from the output of the converter to ground.
LOW_P 25 I Low-power operation mode (active high) input for TPS65251
GND 26 Ground pin
PGOOD 27 O Powergood. Open-drain output asserted after all converters are sequenced and within regulation. Polarity is factory selectable (active high default).
V7V 28 O Internal supply. Connect a 10-μF ceramic capacitor from this pin to ground.
V3V 29 O Internal supply. Connect a 3.3-μF to 10-μF ceramic capacitor from this pin to ground.
AGND 30 Analog ground. Connect all GND pins and the power pad together.
GND 31 Ground pin
VIN 32 I Input supply
VIN 33 I Input supply
VIN 34 I Input supply
GND 35 Ground pin
LX3 36 O Switching node for Buck 3
37
VIN3 38 Input supply for Buck 3. Fit a 10-µF ceramic capacitor close to this pin.
BST3 39 I Bootstrap capacitor for Buck 3. Fit a 47-nF ceramic capacitor from this pin to the switching node.
EN3 40 I Enable pin for Buck 3. A low level signal on this pin disables it. If pin is left open a weak internal pullup to V3V will allow for automatic enable. For a delayed start-up add a small ceramic capacitor from this pin to ground.
PAD — — Power pad. Connect to ground.