SNVS697E January   2011  – December 2016 SM72485

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Control Circuit Overview
      2. 7.3.2 Current Limit
      3. 7.3.3 N-Channel Buck Switch and Driver
      4. 7.3.4 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Start-Up Regulator (VCC)
      2. 7.4.2 Regulation Comparator
      3. 7.4.3 Overvoltage Comparator
      4. 7.4.4 ON-Time Generator and Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Selection of External Components
          1. 8.2.2.1.1  RFB1 and RFB2
          2. 8.2.2.1.2  Fs and RT
          3. 8.2.2.1.3  L1
          4. 8.2.2.1.4  C3
          5. 8.2.2.1.5  C2 and R3
          6. 8.2.2.1.6  ESR and R3
          7. 8.2.2.1.7  RCL
          8. 8.2.2.1.8  D1
          9. 8.2.2.1.9  C1
          10. 8.2.2.1.10 C4
          11. 8.2.2.1.11 C5
        2. 8.2.2.2 Low Output Ripple Configurations
          1. 8.2.2.2.1 Reduced Ripple Configuration
          2. 8.2.2.2.2 Minimum Ripple Configuration
          3. 8.2.2.2.3 Alternate Minimum Ripple Configuration
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    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

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)(2)(3)
MIN MAX UNIT
VIN to GND –0.3 100 V
BST to GND –0.3 114 V
SW to GND (steady-state) –1 V
BST to VCC 100 V
BST to SW 14 V
VCC to GND 14 V
All other inputs to GND –0.3 7 V
Storage temperature, Tstg –55 150 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications.
(3) For detailed information on soldering plastic VSSOP and WSON packages, see Absolute Maximum Ratings for Soldering (SNOA549).

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN MAX UNIT
VIN Input voltage 6 95 V
TJ Operating junction temperature –40 125 °C

6.4 Thermal Information

THERMAL METRIC(1) SM72485 UNIT
DGK (VSSOP) NGU (WSON)
8 PINS 8 PINS
RθJA Junction-to-ambient thermal resistance 139.6 42.3 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 41.8 41.4 °C/W
RθJB Junction-to-board thermal resistance 68.4 20.1 °C/W
ψJT Junction-to-top characterization parameter 4.2 0.4 °C/W
ψJB Junction-to-board characterization parameter 67.5 20.3 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance — 4.1 °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report.

6.5 Electrical Characteristics

Typical values apply for TA = TJ = 25°C, Minimum and Maximum limits apply for TA = TJ = –40°C to 125°C, and VIN = 48 V (unless otherwise noted)(1)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VCC SUPPLY
VCCREG VCC regulator output VIN = 48 V 6.6 7 7.4 V
Dropout voltage, VIN – VCC VIN = 6 V to 8.5 V 100 mV
VCC bypass threshold VIN rising 8.5 V
VCC bypass hysteresis 300 mV
VCC output impedance VIN = 6 V 100 Ω
VIN = 10 V 8.8
VIN = 48 V 0.8
VCC current limit VIN = 48 V 9.2 mA
VCC UVLO VCC rising 5.3 V
VCC UVLO hysteresis 190 mV
VCC UVLO filter delay 3 µs
ICC Operating current VFB = 3 V, VIN = 48 V 550 750 µA
Shutdown current VRT/SD = 0 V 110 176 µA
SWITCH CHARACTERISTICS
Buckswitch RDS(ON) ITEST = 200 mA 2.2 4.6 Ω
Gate drive UVLO VBST – VSW rising 2.8 3.8 4.8 V
Gate drive UVLO hysteresis 490 mV
Precharge switch voltage At 1 mA 0.8 V
Precharge switch on-time 150 ns
CURRENT LIMIT
Current limit threshold 0.24 0.3 0.36 A
Current limit response time ISW overdrive = 0.1 A, time to switch OFF 350 ns
tOFF_1 Off-time generator VFB = 0 V, RCL = 100 kΩ 35 µs
tOFF_2 Off-time generator VFB = 2.3 V, RCL = 100 kΩ 2.56
ON-TIME GENERATOR
tON_1 On-time generator VIN = 10 V, RON = 200 kΩ 2.15 2.77 3.5 µs
tON_2 On-time generator VIN = 95 V, RON = 200 kΩ 200 300 420 ns
Remote shutdown threshold Rising 0.4 0.7 1.05 V
Remote shutdown hysteresis 35 mV
MINIMUM OFF-TIME
Minimum off-time VFB = 0 V 300 ns
REGULATION AND OV COMPARATORS
FB reference threshold Internal reference, trip point for switch = ON 2.445 2.5 2.55 V
FB overvoltage threshold Trip point for switch = OFF 2.875 V
FB bias current 100 nA
THERMAL SHUTDOWN
TSD Thermal shutdown temperature 165 °C
Thermal shutdown hysteresis 25 °C
(1) All limits are ensured. All electrical characteristics having room temperature limits are tested during production with TA = TJ = 25°C. All minimum and maximum limits are ensured by correlating the electrical characteristics to process and temperature variations and applying statistical process control.

6.6 Typical Characteristics

SM72485 30142324.png
Circuit of Figure 10
Figure 1. Efficiency vs Load Current and VIN
SM72485 30142325.png Figure 3. On-Time vs Input Voltage and RT
SM72485 30142326.png Figure 5. Maximum Frequency vs VOUT and VIN
SM72485 30142305.png
Figure 2. VCC vs VIN
SM72485 30142307.gif Figure 4. Current Limit OFF-Time vs VFB and RCL
SM72485 30142327.png Figure 6. ICC Current vs Applied VCC Voltage