SNVSAI4B November   2017  – November 2020 LM5145

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1. 6.1 Wettable Flanks
  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 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  Input Range (VIN)
      2. 8.3.2  Output Voltage Setpoint and Accuracy (FB)
      3. 8.3.3  High-Voltage Bias Supply Regulator (VCC)
      4. 8.3.4  Precision Enable (EN/UVLO)
      5. 8.3.5  Power Good Monitor (PGOOD)
      6. 8.3.6  Switching Frequency (RT, SYNCIN)
        1. 8.3.6.1 Frequency Adjust
        2. 8.3.6.2 Clock Synchronization
      7. 8.3.7  Configurable Soft Start (SS/TRK)
        1. 8.3.7.1 Tracking
      8. 8.3.8  Voltage-Mode Control (COMP)
      9. 8.3.9  Gate Drivers (LO, HO)
      10. 8.3.10 Current Sensing and Overcurrent Protection (ILIM)
      11. 8.3.11 OCP Duty Cycle Limiter
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
      4. 8.4.4 Diode Emulation Mode
      5. 8.4.5 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Design and Implementation
      2. 9.1.2 Power Train Components
        1. 9.1.2.1 Inductor
        2. 9.1.2.2 Output Capacitors
        3. 9.1.2.3 Input Capacitors
        4. 9.1.2.4 Power MOSFETs
      3. 9.1.3 Control Loop Compensation
      4. 9.1.4 EMI Filter Design
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – 20-A High-Efficiency Synchronous Buck Regulator for Telecom Power Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Custom Design With WEBENCH® Tools
        4. 9.2.1.4 Application Curves
      2. 9.2.2 Design 2 – High Density, 12-V, 10-A Rail With LDO Low-Noise Auxiliary Output for RF Power Applications
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Design 3 – 150-W, Regulated 24-V Rail for Commercial Drone Applications With Output Voltage Tracking Feature
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
      4. 9.2.4 Design 4 – Powering a Multicore DSP From a 24-V or 48-V Rail
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
        3. 9.2.4.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Power Stage Layout
      2. 11.1.2 Gate Drive Layout
      3. 11.1.3 PWM Controller Layout
      4. 11.1.4 Thermal Design and Layout
      5. 11.1.5 Ground Plane Design
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
      3. 12.1.3 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
        1. 12.2.1.1 PCB Layout Resources
        2. 12.2.1.2 Thermal Design Resources
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGY|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.5 Electrical Characteristics

Typical values correspond to TJ = 25°C. Minimum and maximum limits apply over the –40°C to 125°C junction temperature range unless otherwise stated. VIN = 48 V, VEN/UVLO = 1.5 V, RRT = 25 kΩ unless otherwise stated.(1)(2)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
INPUT SUPPLY
VIN Operating input voltage range 6 75 V
IQ-RUN Operating input current, not switching VEN/UVLO = 1.5 V, VSS/TRK = 0 V 1.8 2.1 mA
IQ-STBY Standby input current VEN/UVLO = 1 V 1.75 2 mA
IQ-SDN Shutdown input current VEN/UVLO = 0 V, VVCC < 1 V 13.5 16 µA
VCC REGULATOR
VVCC VCC regulation voltage VSS/TRK = 0 V, 9 V ≤ VVIN ≤ 75 V,
0 mA < IVCC ≤ 20 mA		 7.3 7.5 7.7 V
VVCC-LDO VIN to VCC dropout voltage VVIN = 6 V, VSS/TRK = 0 V, IVCC = 20 mA 0.25 0.63 V
ISC-LDO VCC short-circuit current VSS/TRK = 0 V, VVCC = 0 V 40 50 70 mA
VVCC-UV VCC undervoltage threshold VVCC rising 4.8 4.93 5.2 V
VVCC-UVH VCC undervoltage hysteresis Rising threshold – falling threshold 0.26 V
VVCC-EXT Minimum external bias supply voltage Voltage required to disable VCC regulator 8 V
IVCC External VCC input current, not switching VSS/TRK = 0 V, VVCC = 13 V 2.1 mA
ENABLE AND INPUT UVLO
VSDN Shutdown to standby threshold VEN/UVLO rising 0.42 V
VSDN-HYS Shutdown threshold hysteresis EN/UVLO rising – falling threshold 50 mV
VEN Standby to operating threshold VEN/UVLO rising 1.164 1.2 1.236 V
IEN-HYS Standby to operating hysteresis VEN/UVLO = 1.5 V 9 10 11 µA
ERROR AMPLIFIER
VREF FB reference voltage FB connected to COMP 792 800 808 mV
IFB-BIAS FB input bias current VFB = 0.8 V –0.1 0.1 µA
VCOMP-OH COMP output high voltage VFB = 0 V, COMP sourcing 1 mA 5 V
VCOMP-OL COMP output low voltage COMP sinking 1 mA 0.3 V
AVOL DC gain 94 dB
GBW Unity gain bandwidth 6.5 MHz
SOFT-START AND VOLTAGE TRACKING
ISS SS/TRK capacitor charging current VSS/TRK = 0 V 8.5 10 12 µA
RSS SS/TRK discharge FET resistance VEN/UVLO = 1 V, VSS/TRK = 0.1 V 11 Ω
VSS-FB SS/TRK to FB offset –15 15 mV
VSS-CLAMP SS/TRK clamp voltage VSS/TRK – VFB, VFB = 0.8 V 115 mV
POWER GOOD INDICATOR
PGUTH FB upper threshold for PGOOD high to low % of VREF, VFB rising 106% 108% 110%
PGLTH FB lower threshold for PGOOD high to low % of VREF, VFB falling 90% 92% 94%
PGHYS_U PGOOD upper threshold hysteresis % of VREF 3%
PGHYS_L PGOOD lower threshold hysteresis % of VREF 2%
TPG-RISE PGOOD rising filter FB to PGOOD rising edge 25 µs
TPG-FALL PGOOD falling filter FB to PGOOD falling edge 25 µs
VPG-OL PGOOD low state output voltage VFB = 0.9 V, IPGOOD = 2 mA 150 mV
IPG-OH PGOOD high state leakage current VFB = 0.8 V, VPGOOD = 13 V 100 nA
OSCILLATOR
FSW1 Oscillator Frequency – 1 RRT = 100 kΩ 100 kHz
FSW2 Oscillator Frequency – 2 RRT = 25 kΩ 380 400 420 kHz
FSW3 Oscillator Frequency – 3 RRT = 12.5 kΩ 780 kHz
SYNCHRONIZATION INPUT AND OUTPUT
FSYNC SYNCIN external clock frequency range % of nominal frequency set by RRT –20% +50%
VSYNC-IH Minimum SYNCIN input logic high 2 V
VSYNC-IL Maximum SYNCIN input logic low 0.8 V
RSYNCIN SYNCIN input resistance VSYNCIN = 3 V 20 kΩ
tSYNCI-PW SYNCIN input minimum pulsewidth Minimum high state or low state duration 50 ns
VSYNCO-OH SYNCOUT high state output voltage ISYNCOUT = –1 mA (sourcing) 3 V
VSYNCO-OL SYNCOUT low state output voltage ISYNCOUT = 1 mA (sinking) 0.4 V
tSYNCOUT Delay from HO rising to SYNCOUT leading edge VSYNCIN = 0 V, TS = 1/FSW,
FSW set by RRT		 TS/2 – 140 ns
tSYNCIN Delay from SYNCIN leading edge to HO rising 50% to 50% 150 ns
BOOTSTRAP DIODE AND UNDERVOLTAGE THRESHOLD
VBST-FWD Diode forward voltage, VCC to BST VCC to BST, BST pin sourcing 20 mA 0.75 0.9 V
IQ-BST BST to SW quiescent current, not switching VSS/TRK = 0 V, VSW = 48 V, VBST = 54 V 80 µA
VBST-UV BST to SW undervoltage detection VBST – VSW falling 3.4 V
VBST-HYS BST to SW undervoltage hysteresis VBST – VSW rising 0.42 V
PWM CONTROL
tON(MIN) Minimum controllable on-time VBST – VSW = 7 V, HO 50% to 50% 40 60 ns
tOFF(MIN) Minimum off-time VBST – VSW = 7 V, HO 50% to 50% 140 200 ns
DC100kHz Maximum duty cycle FSW = 100 kHz, 6 V ≤ VVIN ≤ 60 V 98% 99%
DC400kHz FSW = 400 kHz, 6 V ≤ VVIN ≤ 60 V 90% 94%
VRAMP(min) Ramp valley voltage (COMP at 0% duty cycle) 300 mV
kFF PWM feedforward gain (VIN / VRAMP) 6 V ≤ VVIN ≤ 75 V 15 V/V
OVERCURRENT PROTECT (OCP) – VALLEY CURRENT LIMITING
IRS ILIM source current, RSENSE mode Low voltage detected at ILIM 90 100 110 µA
IRDSON ILIM source current, RDS(on) mode SW voltage detected at ILIM, TJ = 25°C 180 200 220 µA
IRDSONTC ILIM current tempco RDS-ON mode 4500 ppm/°C
IRSTC ILIM current tempco RSENSE mode 0 ppm/°C
VILIM-TH ILIM comparator threshold at ILIM –8 –2 3.5 mV
SHORT-CIRCUIT PROTECT (SCP) – DUTY CYCLE CLAMP
VCLAMP-OS Clamp offset voltage – no current limiting CLAMP to COMP steady state offset voltage 0.2 + VVIN/75 V
VCLAMP-MIN Minimum clamp voltage CLAMP voltage with continuous current limiting 0.3 + VVIN/150 V
HICCUP MODE FAULT PROTECTION
CHICC-DEL Hiccup mode activation delay Clock cycles with current limiting before hiccup off-time activated 128 cycles
CHICCUP Hiccup mode off-time after activation Clock cycles with no switching followed by SS/TRK release 8192 cycles
DIODE EMULATION
VZCD-SS Zero-cross detect (ZCD) soft-start ramp ZCD threshold measured at SW pin
50 clock cycles after first HO pulse		 0 mV
VZCD-DIS Zero-cross detect disable threshold (CCM) ZCD threshold measured at SW pin
1000 clock cycles after first HO pulse		 200 mV
VDEM-TH Diode emulation zero-cross threshold Measured at SW with VSW rising –5 0 5 mV
GATE DRIVERS
RHO-UP HO high-state resistance, HO to BST VBST – VSW = 7 V, IHO = –100 mA 1.5 Ω
RHO-DOWN HO low-state resistance, HO to SW VBST – VSW = 7 V, IHO = 100 mA 0.9 Ω
RLO-UP LO high-state resistance, LO to VCC VBST – VSW = 7 V, ILO = –100 mA 1.5 Ω
RLO-DOWN LO low-state resistance, LO to PGND VBST – VSW = 7 V, ILO = 100 mA 0.9 Ω
IHOH, ILOH HO, LO source current VBST – VSW = 7 V, HO = SW, LO = AGND 2.3 A
IHOL, ILOL HO, LO sink current VBST – VSW = 7 V, HO = BST, LO = VCC 3.5 A
THERMAL SHUTDOWN
TSD Thermal shutdown threshold TJ rising 175 °C
TSD-HYS Thermal shutdown hysteresis 20 °C
(1) All minimum and maximum limits are specified by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
(2) The junction temperature (TJ in °C) is calculated from the ambient temperature (TA in °C) and power dissipation (PD in Watts) as follows: TJ = TA + (PD • RθJA) where RθJA (in °C/W) is the package thermal impedance provided in Section 7.4.