SLUS851D October   2008  – October 2014 TPS54231

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Pin Configuration 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 Switching Characteristics
    7. 7.7 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  Fixed-Frequency PWM Control
      2. 8.3.2  Voltage Reference (Vref)
      3. 8.3.3  Bootstrap Voltage (BOOT)
      4. 8.3.4  Enable and Adjustable Input Undervoltage Lockout (VIN UVLO)
      5. 8.3.5  Programmable Slow Start Using SS Pin
      6. 8.3.6  Error Amplifier
      7. 8.3.7  Slope Compensation
      8. 8.3.8  Current-Mode Compensation Design
      9. 8.3.9  Overcurrent Protection and Frequency Shift
      10. 8.3.10 Overvoltage Transient Protection
      11. 8.3.11 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Eco-mode™
      2. 8.4.2 Operation With VIN < 3.5 V
      3. 8.4.3 Operation With EN Control
  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 Switching Frequency
        2. 9.2.2.2 Output Voltage Set Point
        3. 9.2.2.3 Input Capacitors
        4. 9.2.2.4 Output Filter Components
          1. 9.2.2.4.1 Inductor Selection
          2. 9.2.2.4.2 Capacitor Selection
        5. 9.2.2.5 Compensation Components
        6. 9.2.2.6 Bootstrap Capacitor
        7. 9.2.2.7 Catch Diode
        8. 9.2.2.8 Output Voltage Limitations
        9. 9.2.2.9 Power Dissipation Estimate
      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 Estimated Circuit Area
    4. 11.4 Electromagnetic Interference (EMI) Considerations
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Trademarks
    3. 12.3 Electrostatic Discharge Caution
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

7 Specifications

7.1 Absolute Maximum Ratings(1)

over operating free-air temperature range (unless otherwise noted)
MIN MAX UNIT
Input voltage VIN –0.3 30 V
EN –0.3 6
BOOT 38
VSENSE –0.3 3
COMP –0.3 3
SS –0.3 3
Output voltage BOOT-PH 8 V
PH –0.6 30
PH (10 ns transient from ground to negative peak) –5
Source current EN 100 μA
BOOT 100 mA
VSENSE 10 μA
PH 6 A
Sink current VIN 6 A
COMP 100 μA
SS 200
Operating junction temperature, TJ –40 150 °C
(1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

7.2 Handling Ratings

MIN MAX UNIT
Tstg Storage temperature range –65 150 °C
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) –2 2 kV
Charged device model (CDM), per JEDEC specification JESD22-C101, all pins(2) –500 500 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

7.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN MAX UNIT
Operating Input Voltage on (VIN pin) 3.5 28 V
TJ Operating junction temperature –40 150 °C

7.4 Thermal Information

THERMAL METRIC(1) D UNIT
8 PINS
RθJA Junction-to-ambient thermal resistance 116.3 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 53.7
RθJB Junction-to-board thermal resistance 57.1
ψJT Junction-to-top characterization parameter 12.9
ψJB Junction-to-board characterization parameter 56.5
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

7.5 Electrical Characteristics

TJ = –40°C to 150°C, VIN = 3.5 to 28 V (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
SUPPLY VOLTAGE (VIN PIN)
Internal undervoltage lockout threshold Rising and falling 3.5 V
Shutdown supply current EN = 0V, VIN = 12V, –40°C to 85°C 1 4 μA
Operating – non switching supply current VSENSE = 0.85 V 75 110 μA
ENABLE AND UVLO (EN PIN)
Enable threshold Rising and falling 1.25 1.35 V
Input current Enable threshold – 50 mV -1 μA
Input current Enable threshold + 50 mV -4 μA
VOLTAGE REFERENCE
Voltage reference 0.772 0.8 0.828 V
HIGH-SIDE MOSFET
On resistance BOOT-PH = 3 V, VIN = 3.5 V 115 200 mΩ
BOOT-PH = 6 V, VIN = 12 V 80 150
ERROR AMPLIFIER
Error amplifier transconductance (gm) –2 μA < I(COMP) < 2 μA, V(COMP) = 1 V 92 μmhos
Error amplifier DC gain(1) VSENSE = 0.8 V 800 V/V
Error amplifier unity gain bandwidth(1) 5 pF capacitance from COMP to GND pins 2.7 MHz
Error amplifier source/sink current V(COMP) = 1 V, 100-mV overdrive ±7 μA
Switch current to COMP transconductance VIN = 12 V 9 A/V
PULSE SKIPPING ECO-MODE
Pulse skipping Eco-mode™ switch current threshold 100 mA
CURRENT LIMIT
Current limit threshold VIN = 12 V 2.3 3.5 5.3 A
THERMAL SHUTDOWN
Thermal Shutdown 165 °C
SLOW START (SS PIN)
Charge current V(SS) = 0.4 V 2 μA
SS to VSENSE matching V(SS) = 0.4 V 10 mV
(1) Specified by design.

7.6 Switching Characteristics

TJ = –40°C to 150°C, VIN = 3.5 to 28 V (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
SWITCHING FREQUENCY
TPS54231 device switching frequency VIN = 12 V 400 570 740 kHz
Minimum controllable on time VIN = 12 V, 25°C 105 130 ns
Maximum controllable duty ratio(1) BOOT-PH = 6 V 90% 93%
(1) Specified by design.

7.7 Typical Characteristics

rdson_tj_lus851.gif
Figure 1. ON Resistance vs Junction Temperature
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Figure 3. Switching Frequency vs Junction Temperature
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Figure 5. Minimum Controllable ON Time vs Junction Temperature
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Figure 7. SS Charge Current vs Junction Temperature
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Figure 2. Shutdown Quiescent Current vs Input Voltage
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Figure 4. Voltage Reference vs Junction Temperature
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Figure 6. Minimum Controllable Duty Ratio vs Junction Temperature
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Figure 8. Current-Limit Threshold vs Input Voltage